# Patent-Eligible Subject Matter Reform: Background and Issues for Congress

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URL: https://www.frixlaw.com/law-library/documents/crs%3AR45918

## Record

- **Collection:** Congressional research report
- **Document type:** Reports
- **Published:** March 31, 2025
- **Citation:** R45918

## Text

Patent-Eligible Subject Matter Reform:
Background and Issues for Congress
Updated March 31, 2025

Congressional Research Service
https://crsreports.congress.gov
R45918

SUMMARY

Patent-Eligible Subject Matter Reform:
Background and Issues for Congress

R45918
March 31, 2025
Kevin J. Hickey

Legislative Attorney
The statutory definition of patent-eligible subject matter under Section 101 of the Patent Act (35
U.S.C. § 101) has remained essentially unchanged for more than two centuries. As a result, the
scope of patentable subject matter—that is, the types of inventions that may be patented—has
largely been left to the federal courts to develop through “common law”-like adjudication. In the
20th century, the U.S. Supreme Court established that three main types of discoveries are
categorically patent-ineligible when claimed as such: laws of nature, natural phenomena, and abstract ideas.

A series of Supreme Court decisions in the 2010s broadened the scope of these three judicial exceptions to patent-eligible
subject matter. Over a five-year period, the Supreme Court rejected, as ineligible, patents on a business method for hedging
price-fluctuation risk (Bilski v. Kappos, 561 U.S. 593 (2010)); a method for calibrating the dosage of a particular drug (Mayo
Collaborative Services v. Prometheus Laboratories, 566 U.S. 66 (2012)); isolated human DNA segments (Ass’n for
Molecular Pathology v. Myriad Genetics, Inc., 569 U.S. 576 (2013)); and a method of mitigating settlement risk in financial
transactions using a computer (Alice Corp. Pty. v. CLS Bank International, 573 U.S. 208 (2014)). These cases established a
new two-step test, known as the Alice/Mayo framework, for determining whether a patent claims ineligible subject matter.
The first step of the Alice/Mayo test addresses whether the patent claims are “directed to” a law of nature, natural
phenomenon, or abstract idea. If not, the invention is patentable. If the claims are directed to one of the ineligible categories,
then the second step of the Alice/Mayo test asks whether the patent claims have an “inventive concept.” To have an inventive
concept, the patent claim must contain elements that transform the nature of the claim into a patent-eligible application of the
ineligible concept, so that the claim amounts, in practice, to something “significantly more” than a patent on the ineligible
concept itself. If the claimed invention lacks an inventive concept, then it is patent-ineligible.
The Supreme Court’s decisions have been widely recognized to effect a major change in the scope of patentable subject
matter, restricting the sorts of inventions that are patentable in the United States. The Alice/Mayo test has been the subject of
criticism, with some stakeholders arguing that the Alice/Mayo framework is vague and unpredictable, unduly restricts the
scope of patentable subject matter, reduces incentives to invest and innovate, and harms American industry’s
competitiveness. In particular, these stakeholders argue that the Alice/Mayo test creates uncertainty in the computer
technology and biotechnology industries as to whether innovations in medical diagnostics, personalized medicine, methods of
treatment, computer software, and artificial intelligence are patent-eligible. Such stakeholders—including academics, bar
associations, industry representatives, judges, and former U.S. Patent and Trademark Office (USPTO) officials—have called
for the Supreme Court or Congress to act to change the law of patentable subject matter.
Other stakeholders defend the legal status quo, arguing that the Alice/Mayo framework provides an important tool for
combating unmeritorious patent litigation, or that the revitalized limits on patentable subject matter have important benefits
for innovation. For example, some civil liberty and nonprofit organizations generally support the Alice/Mayo framework,
which they argue helps foster invention and innovation by preventing monopolies on basic research tools and concepts.
The past decade has seen a number of judicial, administrative, and legislative developments in patent-eligible subject matter
law and potential reforms responding to the Alice/Mayo decisions. On the judicial front, the Supreme Court has declined to
hear further cases on the topic, despite calls by prominent stakeholders and judges on the U.S. Court of Appeals for the
Federal Circuit. On the administrative front, the USPTO issued updated guidance in 2019 and 2024 to clarify and improve
predictability in how USPTO patent examiners make Section 101 determinations, and released several reports on the topic. In
Congress, several bills introduced in the 117th and 118th Congresses would have abrogated the Supreme Court’s recent
decisions on patent-eligible subject matter and otherwise reformed the statutory standards for patent-eligible subject matter.
Proposed changes to patent-eligible subject matter standards could have significant effects as to the types of technologies that
are patentable. The availability of patent rights, in turn, affects incentives to invest and innovate in particular fields, as well as
consumer costs and public access to technological innovation. Understanding the legal background and context of this
complex issue may aid Congress as it debates the legal and practical effects that legislative Section 101 reforms would have
if enacted.

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Contents
Patent Law Background .................................................................................................................. 4
Requirements for Patentability .................................................................................................. 5
Section 101: Utility ............................................................................................................. 5
Section 102: Novelty........................................................................................................... 5
Section 103: Nonobviousness ............................................................................................. 6
Section 112(a): Written Description, Enablement, Best Mode ........................................... 6
Patent Claims ............................................................................................................................ 7
Section 112(b): Definiteness ............................................................................................... 7
Section 112(f): Functional Claiming ................................................................................... 7
Rights of Patent Holders ........................................................................................................... 8
Defending Against Patent Suits ................................................................................................. 9
The Law of Section 101 .................................................................................................................11
Historical Development of the Judicial Exceptions to Patent-Eligible Subject Matter ........... 12
Nineteenth Century ........................................................................................................... 12
Twentieth Century ............................................................................................................. 14
The Modern Alice/Mayo Framework ...................................................................................... 16
The Debate Over Alice/Mayo and Section 101 Reform ................................................................ 20
Criticisms of the Alice/Mayo Framework ............................................................................... 20
Defenses of the Alice/Mayo Framework ................................................................................. 23
Views on the Purposes of Section 101 .................................................................................... 24
Potential Options for Section 101 Reform .............................................................................. 26
Continued Common Law Judicial Development .............................................................. 26
Specific Statutory List of Included or Excluded Subject Matter Categories .................... 27
Replace Judicial Exceptions with a Different Standard .................................................... 28
Eliminate Implied Patentable Subject Matter Limits ........................................................ 29
Post-Alice Developments in Patent-Eligible Subject Matter Law and Proposed Reforms............ 30
Judicial Developments ............................................................................................................ 30
Administrative Developments in the USPTO ......................................................................... 31
The 2019 Revised Patent Subject Matter Eligibility Guidance ........................................ 31
2022 USPTO Report on Stakeholder Views ..................................................................... 34
2024 Artificial Intelligence Eligibility Guidance .............................................................. 34
Legislative Developments ....................................................................................................... 36
The 116th Congress .......................................................................................................... 36
The 117th Congress .......................................................................................................... 40
The 118th Congress .......................................................................................................... 42
Conclusion ..................................................................................................................................... 43

Tables
Table 1. Major Supreme Court Decisions on Patentable Subject Matter ...................................... 18

Contacts
Author Information........................................................................................................................ 43

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T

he statutory language governing patent-eligible subject matter—that is, the types of
inventions that may be patented—has remained remarkably constant over the nearly 250year history of U.S. patent law.1 Under the Patent Act of 1793, which Thomas Jefferson
authored,2 “any new and useful art, machine, manufacture or composition of matter, or any new
and useful improvement [of the same]” was patentable.3 Current law—Section 101 of the Patent
Act of 1952—permits the patenting of “any new and useful process, machine, manufacture, or
composition of matter, or any new and useful improvement thereof.”4 Through these four
expansive statutory categories,5 Congress sought to ensure that nearly “anything under the sun
made by man” is patentable6 if it meets all the requirements for patentability, such as novelty,
enablement, and nonobviousness.7
Consistent with its broad statutory language, Section 101 permits patenting in fields of applied
technology such as pharmaceuticals, biotechnology, chemistry, computer hardware and software,
electrical engineering, agriculture, mechanical engineering, and manufacturing processes.8 Even
so, the Supreme Court has long read Section 101 as categorically prohibiting patents on three
types of discoveries: “laws of nature, natural phenomena, and abstract ideas.”9 Even if “not
required by the statutory text” of Section 101, the Court has held that these three judicial

1 See generally Diamond v. Chakrabarty, 447 U.S. 303, 308–09 (1980) (tracing the history of statutory language on

patentable subject matter). This observation—and this report more generally—is limited to traditional utility patents on
useful inventions and discoveries. See 35 U.S.C. §§ 100–135. Congress did not provide patent protection for “original
and ornamental designs for an article of manufacture” (design patents), id. §§ 171–173, and for “distinct and new
variet[ies] of plants” (plant patents), id. §§ 161–164, until 1842 and 1930, respectively. See An Act in addition to an act
to promote the progress of the useful arts, and to repeal all acts and parts of acts heretofore made for that purpose, Pub.
L. No. 27-263, 5 Stat. 543 (1842); An Act to provide for plant patents, Pub. L. No. 71-245, 46 Stat. 376 (1930).
2 Graham v. John Deere Co. of Kan. City, 383 U.S. 1, 7 (1966) (describing Jefferson as “the author of the 1793 Patent
Act”).
3 An Act to promote the progress of useful Arts; and to repeal the act heretofore made for that purpose, Pub. L. No. 211, § 1, 1 Stat. 318, 319 (1793). The first Patent Act, enacted in 1790, had phrased things slightly differently: “any
useful art, manufacture, engine, machine, or device, or any improvement therein.” See An Act to promote the progress
of useful Arts, Pub. L. No. 1-7, § 1, 1 Stat. 109, 110 (1790). The Patent Acts of 1836 and 1870 used nearly identical
language as the 1793 Patent Act. See An Act to promote the progress of useful arts, and to repeal all acts and parts of
acts heretofore made for that purpose, Pub. L. No. 24-357, § 6, 5 Stat. 117, 119 (1836); An Act to revise, consolidate,
and amend the Statutes relating to Patents and Copyrights, Pub. L. No. 41-230, § 24, 16 Stat. 198, 201 (1870). In 1952,
Congress replaced the term “art,” historically used to mean a process or method, with the more modern term “process,”
while defining “process” to mean “process, art, or method.” Patent Act of 1952, Pub. L. No. 82-593, §§ 100–101, 66
Stat. 792, 797; see also 1 CHISUM ON PATENTS, Overview: Historical Development of Patent Law, § 2 n.4 (2019) (“[As
used in the 1793 Patent Act, t]he term ‘art’ meant process or method.”); Bilski v. Kappos, 561 U.S. 593, 639 (2010)
(Stevens, J., concurring) (“That change [from ‘art’ to ‘process’] was made for clarity and did not alter the scope of a
patentable ‘process.’” (citing Diamond v. Diehr, 450 U.S. 175, 184 (1981))); The Telephone Cases, 126 U.S. 1, 532
(1888) (“this art—or, what is the same thing under the patent law, this process . . .”).
4 35 U.S.C. § 101.
5 Chakrabarty, 447 U.S. at 308 (“In choosing such expansive terms as ‘manufacture’ and ‘composition of matter,’
modified by the comprehensive ‘any,’ Congress plainly contemplated that the patent laws would be given wide
scope.”).
6 Id. at 309 (quoting S. Rep. No. 1979, 82d Cong., 2d Sess., 5 (1952); H. R. Rep. No. 1923, 82d Cong., 2d Sess., 6
(1952)).
7 See 35 U.S.C. §§ 102–103, 112; see generally infra “Requirements for Patentability.”
8 See Patent Technology Centers Management, U.S. PAT. & TRADEMARK OFF., https://www.uspto.gov/patent/contactpatents/patent-technology-centers-management (last visited Mar. 6, 2025) (listing technological divisions for USPTO
examiners).
9 Diehr, 450 U.S. at 185.

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exceptions “define[] the reach of the statute as a matter of statutory stare decisis going back 150
years.”10
In a series of decisions in the 2010s, the Supreme Court relied on Section 101 to reject patent
claims on
•
•
•
•

a method for hedging price-fluctuation risks in commodity markets;11
a method for measuring metabolites in human blood to calibrate the dosage of
particular drug;12
isolated human DNA segments;13 and
a method of mitigating settlement risk in financial transactions using a
computer.14

These cases established a two-step test for patentable subject matter sometimes called the
“Alice/Mayo test” or the “Alice/Mayo framework.”15 The Court’s decisions have been widely
recognized to effect a major change in the scope of patentable subject matter, restricting the sorts
of inventions that are patentable in the United States.16 The Alice/Mayo framework has thus
shifted, for better or worse, the balance between encouraging innovation and the social costs of
exclusive rights that is at the heart of patent law.17 The effects of this change have been
particularly pronounced for computer technologies and biomedical technologies.18
As a result, there is a significant and ongoing debate about the Alice/Mayo framework, with a
number of patent law stakeholders questioning the Court’s patentable subject matter rulings.19
Critics argue that the Alice/Mayo framework is vague, unpredictable, and not administrable;20
10 Bilski v. Kappos, 561 U.S. 593, 602 (2010) (citing Le Roy v. Tatham, 55 U.S. (14 How.) 156, 174–75 (1853)).
11 Id. at 611–12.
12 Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 77–80 (2012).
13 Ass’n for Molecular Pathology v. Myriad Genetics, Inc., 569 U.S. 576, 590–94 (2013).
14 Alice Corp. Pty. v. CLS Bank Int’l, 573 U.S. 208, 218–26 (2014).
15 See, e.g., Aatrix Software, Inc. v. Green Shades Software, Inc., 882 F.3d 1121, 1126, 1128 (Fed. Cir. 2018) (referring

to the inquiry as the “Alice/Mayo test” or the “Alice/Mayo analysis”). The Supreme Court refers to the two-step process
first set forth in Mayo as a “framework.” Alice, 573 U.S. at 217.
16 See U.S. PATENT & TRADEMARK OFF., PATENT ELIGIBLE SUBJECT MATTER: REPORT ON VIEWS AND
RECOMMENDATIONS FROM THE PUBLIC 23 (2017), https://www.uspto.gov/sites/default/files/documents/101Report_FINAL.pdf [hereinafter USPTO PSM REPORT] (“In general, commentators agreed that the Court decisions in
Bilski, Mayo, Myriad, and Alice have had a significant impact on the scope of patent eligible subject matter.”); Jeffrey
A. Lefstin et al., Final Report of the Berkeley Center for Law & Technology Section 101 Workshop: Addressing Patent
Eligibility Challenges, 33 BERKELEY TECH. L.J. 551, 555–59 (2018) [hereinafter BCLT Report] (describing these
Supreme Court opinions as a “sea-change”).
17 See Bonito Boats, Inc. v. Thunder Craft Boats, Inc., 489 U.S. 141, 146 (1989) (“From their inception, the federal
patent laws have embodied a careful balance between the need to promote innovation and the recognition that imitation
and refinement through imitation are both necessary to invention itself and the very lifeblood of a competitive
economy.”); Mark A. Lemley, Property, Intellectual Property, and Free Riding, 83 TEX. L. REV. 1031, 1031 (2005)
(“[Traditionally,] the proper goal of intellectual property law is to give as little protection as possible consistent with
encouraging innovation.”).
18 See USPTO PSM REPORT, supra note 16, at 34–35 (finding “a general consensus that two industries have been most
directly affected by the recent Supreme Court jurisprudence: life sciences and computer-related technologies”).
19 See generally id. at 27–34 (summarizing public comments that the Alice/Mayo framework is legally flawed, overly
broad, unpredictable, and harmful to innovation).
20 Id. at 29–30 (describing public views that the Supreme Court “has failed to articulate objective, predictable criteria”
for patentable subject matter); Hon. Paul R. Michel, The Supreme Court Saps Patent Certainty, 82 GEO. WASH. L. REV.
1751, 1758 (2014) (criticizing Court’s modern Section 101 jurisprudence as “subjective,” “indeterminate,” and “highly
(continued...)

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muddies patent law by confusing patent eligibility with distinct patent law concerns, such as
nonobviousness;21 reduces incentives to innovate and invest in particular industries, such as
biotechnology;22 or puts U.S. industry at a disadvantage with international competitors.23 Other
stakeholders defend the Alice/Mayo framework, arguing that the Court’s decisions are a part of
the ordinary common law development of Section 101;24 an important tool for combating
unmeritorious litigation25 or preventing overbroad or otherwise harmful patents;26 or beneficial to
American consumers by lowering prices.27
In response to stakeholder concerns, there have been a number of administrative and legislative
developments that seek to clarify or reform the law of Section 101. In 2019, the U.S. Patent and
Trademark Office (USPTO) issued Revised Patent Subject Matter Eligibility Guidance designed
to assist USPTO patent examiners in determining patent eligibility with greater clarity and
predictability.28 In the 116th Congress, the Senate Judiciary Committee’s Intellectual Property
Subcommittee held a series of hearings on Section 101 reform, seeking input on reform proposals

unpredictable”); David O. Taylor, Confusing Patent Eligibility, 84 TENN. L. REV. 157, 158–60 (2016) (arguing that the
Supreme Court’s Section 101 jurisprudence has created a “crisis of confusion” in patent law and that the doctrine
“lacks administrability”).
21 See USPTO PSM REPORT, supra note 16, at 31–32; Michael Risch, Everything Is Patentable, 75 TENN. L. REV. 591,
598–606 (2008) (arguing that patentability criteria such as obviousness, novelty, utility, inventorship, written
description, and enablement motivate the Supreme Court’s patentable subject matter decisions). But see Mark A.
Lemley et al., Life After Bilski, 63 STAN. L. REV. 1315, 1319–32 (2011) (arguing that the preemption/overbreadth
concerns driving Section 101 are distinct from disclosure and definiteness concerns under Section 112).
22 See, e.g., USPTO PSM REPORT, supra note 16, at 32–33, 35–38; BCLT Report, supra note 16, at 582–84; Taylor,
supra note 20, at 240 (“[The Alice/Mayo framework] substantially reduces incentives to invest in research and
development, particularly in the biotechnology and software technology areas.”).
23 See USPTO PSM REPORT, supra note 16, at 34; Ryan Davis, Kappos Calls for Abolition of Section 101 of Patent
Act, LAW360 (Apr. 12, 2016), https://www.law360.com/articles/783604/kappos-calls-for-abolition-of-section-101-ofpatent-act (quoting former USPTO Director David Kappos as stating that international competitors “no longer have to
steal U.S. technology in [biotechnology and software], since they can now take it for free”); Robert L. Stoll, Courts Are
Making Bad Patent Law, THE HILL (July 16, 2015), https://thehill.com/blogs/pundits-blog/the-judiciary/248054-courtsare-making-bad-patent-law (“The courts’ focus on subject matter eligibility as a mechanism to deny patents for
[inventions in diagnostics and personalized medicine] will drive investment into research in these technologies to other
areas. We will lose our edge in the world . . . .”).
24 See USPTO PSM REPORT, supra note 16, at 23–24.
25 See id. at 24; BCLT Report, supra note 16, at 555 (“Many technology companies that rely on software innovation . . .
welcomed the tightening of patent eligibility standards on software claims and the opportunity to seek early dismissals
of lawsuits.”); Paul R. Gugliuzza, Quick Decisions in Patent Cases, 106 GEO. L.J. 619, 652–53 (2018) (“The
invigoration of the [patent] eligibility requirement can help courts resolve infringement disputes more quickly and
cheaply by allowing validity to be resolved on the pleadings as a matter of law.”).
26 See The State of Patent Eligibility in America: Part I: Hearing Before the S. Judiciary Comm., Subcomm. on
Intellectual Property, 116th Cong. (2019) (statement of Prof. Joshua D. Sarnoff, DePaul University College of Law), at
3–8, https://www.judiciary.senate.gov/download/sarnoff-testimony [hereinafter Sarnoff Testimony]; accord Mayo
Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 86 (2012) (“[E]ven though rewarding with patents those
who discover new laws of nature and the like might well encourage their discovery, those laws and principles,
considered generally, are the basic tools of scientific and technological work. And so there is a danger that the grant of
patents that tie up their use will inhibit future innovation . . . .” (citations omitted)); Lemley et al., supra note 21, at
1329 (arguing that Section 101’s abstract ideas doctrine is “about encouraging cumulative innovation and furthering
societal norms regarding access to knowledge”).
27 USPTO PSM REPORT, supra note 16, at 27.
28 Notice, 2019 Revised Patent Subject Matter Eligibility Guidance, 84 Fed. Reg. 50 (Jan. 7, 2019). The USPTO
subsequently issued an update to this guidance in October 2019. See U.S. PAT. & TRADEMARK OFF., October 2019
Update: Subject Matter Eligibility (Oct. 2019),
https://www.uspto.gov/sites/default/files/documents/peg_oct_2019_update.pdf.

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from various patent stakeholders.29 These efforts led to the introduction of the Patent Eligibility
Restoration Act in the 117th and 118th Congresses.30 Separately, the Restoring America’s
Leadership in Innovation Act has been introduced in recent Congresses and would have reformed
Section 101 (along with several other changes to patent law).31
This report provides the necessary background and context to understand the legal and practical
effects that these legislative reforms would have if enacted.32 First, the report reviews the basic
legal principles of the U.S. patent system. Second, it examines the historical development and
current state of patentable subject matter law. Third, it reviews several articulated rationales for
Section 101 and potential options for Section 101 reform. Finally, it examines recent judicial,
administrative, and legislative developments concerning patent-eligible subject matter, including
the proposed legislative reforms to Section 101.
This report focuses on patent-eligible subject matter reform from a legal perspective. For an
analysis of these issues as they relate to innovation policy, see CRS Report R47267, Patents and
Innovation Policy, by Emily G. Blevins (2022).

Patent Law Background
Congress’s authority to grant patents derives from the Intellectual Property (IP) Clause of the U.S.
Constitution, which grants Congress the power “[t]o promote the Progress of Science and useful
Arts, by securing for limited Times to . . . Inventors the exclusive Right to their . . .
Discoveries.”33 Patents are generally available to any person who “invents or discovers any new
and useful process, machine, manufacture, or composition of matter, or any new and useful
improvement thereof.”34
Patent rights do not arise automatically. Rather, to obtain patent protection under the Patent Act,35
an inventor must formally apply for a patent with the USPTO, beginning a process called patent
prosecution.36 During prosecution, a USPTO patent examiner evaluates the patent application to
29 See generally Sen. Chris Coons & Sen. Thom Tillis, What Coons and Tillis Learned at Patent Reform Hearings,

LAW360 (June 21, 2019), https://www.law360.com/articles/1171672/. Video of the hearings and the written testimony
are available online. See The State of Patent Eligibility in America: Part I: Hearing Before the S. Judiciary Comm.,
Subcomm. on Intellectual Property, 116th Cong. (2019), https://www.judiciary.senate.gov/meetings/the-state-of-patenteligibility-in-america-part-i; The State of Patent Eligibility in America: Part II: Hearing Before the S. Judiciary
Comm., Subcomm. on Intellectual Property, 116th Cong. (2019), https://www.judiciary.senate.gov/meetings/the-stateof-patent-eligibility-in-america-part-ii; The State of Patent Eligibility in America: Part III: Hearing Before the S.
Judiciary Comm., Subcomm. on Intellectual Property, 116th Cong. (2019),
https://www.judiciary.senate.gov/meetings/the-state-of-patent-eligibility-in-america-part-iii [hereinafter, collectively,
Patent Eligibility Hearings].
30 See Patent Eligibility Restoration Act of 2024, H.R. 9474, 118th Cong. (2024); Patent Eligibility Restoration Act of
2023, S. 2140, 118th Cong. (2023); Patent Eligibility Restoration Act of 2022, S. 4734, 117th Cong. (2022).
31 See Restoring America’s Leadership in Innovation Act of 2024, H.R. 8134, 118th Cong. § 7 (2024); Restoring
America’s Leadership in Innovation Act of 2021, H.R. 5874, 117th Cong. § 7 (2021); Restoring America’s Leadership
in Innovation Act of 2020, H.R. 7366, 116th Cong. § 7 (2020); Restoring America’s Leadership in Innovation Act of
2018, H.R. 6264, 115th Cong. § 7 (2018).
32 For a succinct overview of this topic, see CRS In Focus IF12563, Patent-Eligible Subject Matter Reform: An
Overview, by Emily G. Blevins and Kevin J. Hickey (2024).
33 U.S. CONST. art. I, § 8, cl. 8.
34 35 U.S.C. § 101.
35 See Patent Act of 1952, Pub. L. No. 82-593, 66 Stat. 792 (codified as amended at 35 U.S.C. §§ 1–390).
36 See Applying for Patents, U.S. PAT. & TRADEMARK OFF., https://www.uspto.gov/patents/basics/apply (last visited
Mar. 6, 2025).

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ensure that it meets all the applicable legal requirements to merit the grant of a patent.37 To be
patentable, an invention must be (1) directed at patent-eligible subject matter, (2) useful, (3) new,
(4) nonobvious, and (5) adequately disclosed and claimed in the patent application.38 If the
USPTO finds these requirements met, it will issue (i.e., grant) the patent.39 Patents typically
expire 20 years after the initial patent application.40
The current law of patent-eligible subject matter will be discussed separately in detail below.41
The remainder of this section briefly reviews the other requirements for patentability, the scope
and effect of patent claims, and the legal rights granted to the holder of a valid patent.

Requirements for Patentability
Section 101: Utility
Along with its subject matter requirements, Section 101 contains a requirement that a patented
invention must be “useful.”42 In particular, courts have held that an invention must have both a
specific and substantial utility to be patentable.43 The utility requirement derives from the
Constitution’s command that patent laws exist to “promote the Progress of . . . useful Arts.”44 The
constitutional purpose of patent law thus requires a “benefit derived by the public from an
invention with substantial utility,” where the “specific benefit exists in currently available
form.”45 This standard for utility is low, however, requiring only that the claimed invention have
some “significant and presently available benefit to the public” that “is not so vague as to be
meaningless.”46

Section 102: Novelty
Perhaps the most fundamental requirement for patentability is that the claimed invention must be
new. The USPTO will not issue a patent if “the claimed invention was patented, described in a
printed publication, or in public use, on sale, or otherwise available to the public before the
effective filing date of the claimed invention.”47 In other words, if every element of the claimed
invention is already disclosed in the “prior art”—the information available to the public at the
time of the patent application—then the alleged inventor “has added nothing to the total stock of
knowledge,” and no valid patent may issue to her.48

37 35 U.S.C. § 131.
38 See id. §§ 101–103, 112.
39 Id. § 131.
40 Id. § 154(a)(2).
41 See infra “The Law of Section 101.”
42 35 U.S.C. § 101.
43 Brenner v. Manson, 383 U.S. 519, 534–35 (1966); In re Fisher, 421 F.3d 1365, 1371 (Fed. Cir. 2005).
44 Stiftung v. Renishaw PLC, 945 F.2d 1173, 1180 (Fed. Cir. 1991) (citing Brenner, 383 U.S. at 528–29).
45 Brenner, 383 U.S. at 534–35.
46 In re Fisher, 421 F.3d at 1371–72.
47 35 U.S.C. § 102(a)(1). There are certain exceptions to this requirement when, for example, the prior-art disclosure

derives from the inventor and the patent application is made within one year of the disclosure. Id. § 102(b)(1).
48 Great Atl. & Pac. Tea Co. v. Supermarket Equip. Corp., 340 U.S. 147, 153 (1950); Graham v. John Deere Co. of
Kan. City, 383 U.S. 1, 6 (1966) (“Congress may not authorize the issuance of patents whose effects are to remove
existent knowledge from the public domain, or to restrict free access to materials already available.”).

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Section 103: Nonobviousness
Even if a claimed invention is novel in the narrow sense that it is not “identically disclosed” in a
prior-art reference (such as an earlier patent or publication), the invention must further be
nonobvious to be patentable.49 Specifically, an invention cannot be patented if “the differences
between the claimed invention and the prior art are such that the claimed invention as a whole
would have been obvious . . . to a person having ordinary skill” in the relevant technology.50
When determining obviousness, courts also evaluate secondary considerations (also known as
“objective indicia”) of nonobviousness such as “commercial success, long felt but unsolved
needs, [or] failure of others . . . to give light to the circumstances surrounding the origin of the
subject matter sought to be patented.”51 By its nature, obviousness is an “expansive and flexible”
inquiry that cannot be reduced to narrow, rigid tests.52 Nonetheless, if an invention merely
combines “familiar elements according to known methods,” yielding only “predictable results,” it
is likely to be obvious.53

Section 112(a): Written Description, Enablement, Best Mode
Finally, the Patent Act imposes several requirements relating to the technical disclosures in the
patent application. These provisions are intended to ensure that the patent adequately describes
the invention such that the public can use the invention after the expiration of the patent term. 54
Section 112(a) of the Patent Act requires that patents must contain a “specification” that includes
a written description of the invention, and of the manner and process of making and using
it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to
. . . make and use the same, and shall set forth the best mode contemplated by
the inventor or joint inventor of carrying out the invention.55

This statutory language yields three basic disclosure requirements for patentability.56 First, to
satisfy the written description requirement, the specification must “reasonably convey[] to those
skilled in the art that the inventor had possession of the claimed subject matter as of the filing
date” of the patent application.57 Second, to satisfy the enablement requirement, the specification
must contain enough information to teach a person skilled in the art how “to make and use the
invention without undue experimentation.”58 Finally, to satisfy the best mode requirement, if the
inventor knew of a preferred way of practicing her invention at the time of the patent application,
the specification must disclose that “preferred embodiment[]” of the invention.59
49 35 U.S.C. § 103.
50 Id. Patent law often relies on the concept of a “person having ordinary skill in the art,” a “hypothetical person” with a

typical level of skill in the relevant technology who is “presumed to be aware of all the pertinent prior art” in the
particular field. See Standard Oil Co. v. Am. Cyanamid Co., 774 F.2d 448, 454 (Fed. Cir. 1985).
51 Graham, 383 U.S. at 17–18; see also Apple Inc. v. Samsung Elecs. Co., 839 F.3d 1034, 1048 (Fed. Cir. 2016) (en
banc) (“Objective indicia of nonobviousness must be considered in every case where present.).
52 KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 415–19 (2007).
53 Id. at 416.
54 See Kewanee Oil Co. v. Bicron Corp., 416 U.S. 470, 480–81 (1974).
55 35 U.S.C. § 112(a) (emphases added).
56 See Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 736 (2002); Ariad Pharms., Inc. v. Eli
Lilly & Co., 598 F.3d 1336, 1344 (Fed. Cir. 2010) (en banc).
57 Ariad, 598 F.3d at 1351.
58 In re Wands, 858 F.2d 731, 735 (Fed. Cir. 1988).
59 Eli Lilly & Co. v. Barr Labs., Inc., 251 F.3d 955, 963 (Fed. Cir. 2001). Failure to disclose the best mode is not a basis
on which a patent claim can be invalidated in subsequent patent infringement proceedings. 35 U.S.C. § 282(b)(3)(A).

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Patent Claims
Section 112(b): Definiteness
If granted, the legal scope of the patent is defined by the patent claims, a sequence of statements
that formally set forth the patentee’s asserted rights. In essence, while the specification explains
the invention in a technical sense, the claims set forth the legal effect of the patent.60 Much as a
deed may describe the boundaries of a tract of land, the claims define the “metes and bounds” of
the patent right.61 Patent claims must be sufficiently definite to be valid—that is, they must
“particularly point[] out and distinctly claim[] the subject matter which the inventor . . . regards as
the invention.”62 In other words, when the claims are read in context, they must “inform, with
reasonable certainty, those skilled in the art about the scope of the invention.”63

Section 112(f): Functional Claiming
For the most part, the current Patent Act uses a system of peripheral claiming, in which the patent
claims formally set out the outer boundaries of the patentee’s rights.64 However, the Patent Act
still retains elements of its former system of central claiming, in which the patentee would
describe the core principles or examples of what he had invented, but need not formally delineate
the outer boundaries of his rights.65 For example, under the doctrine of equivalents, an accused
infringer may be found liable even if his product does not literally meet every element of the
patent claims, if the differences between a claim element and its alleged equivalent in the accused
product are “insubstantial.”66

60 See Ariad, 598 F.3d at 1347 (Fed. Cir. 2010); In re Vamco Mach. & Tool, Inc., 752 F.2d 1564, 1577 n.5 (Fed. Cir.

1985).
61 Corning Glass Works v. Sumitomo Elec. U.S.A., Inc., 868 F.2d 1251, 1257 (Fed. Cir. 1989).
62 35 U.S.C. § 112(b); Laitram Corp. v. NEC Corp., 163 F.3d 1342, 1347 (Fed. Cir. 1998) (“[I]t is the claims, not the
written description, which define the scope of the patent right.”).
63 Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898, 901 (2014).
64 See 35 U.S.C. § 112(b); Mark A. Lemley, Software Patents and the Return of Functional Claiming, 2013 WIS. L.
REV. 905, 911 (2013) (“Today, peripheral claiming is universal [in patent law]; patentees write claims in an effort to
define the outer boundaries of their invention.”); Jeanne C. Fromer, Claiming Intellectual Property, 76 U. CHI. L. REV.
719, 725–30 (2009) (explaining the distinction between peripheral and central claiming systems for intellectual
property). Until the late 19th century, however, central claiming prevailed: the patentee had only to describe the core
principle or an example of his invention, and courts would decide whether the accused infringer’s product or method
was sufficiently similar to the patentee’s invention to infringe the patent. See Lemley, supra, at 910–11; Fromer, supra,
at 731–33. Peripheral claiming began as a defensive strategy by patentees to describe their invention at a higher level of
generality, and the gradual switch toward the modern patent claiming was eventually codified in the Patent Act in 1870.
See An Act to revise, consolidate, and amend the Statutes relating to Patents and Copyrights, Pub. L. No. 41-230 § 26,
16 Stat. 198, 201 (1870) (requiring patent applicant to “particularly point out and distinctly claim the part,
improvement, or combination which he claims as his invention or discovery”); see generally Fromer, supra, at 731–35
(reviewing American patent law’s historical shift from central to peripheral claiming); Dan L. Burk & Mark A. Lemley,
Fence Posts or Sign Posts? Rethinking Patent Claim Construction, 157 U. PA. L. REV. 1743, 1766–71 (2009) (same).
This account of patent-claiming history is somewhat simplified: notably, despite the 1870 statutory shift, the Patent Act
retained (and retains) features of central claiming. See Burk & Lemley, supra, at 1771 (“[I]t may be fairer to say that
during the twentieth century we had not a peripheral-claiming system, but a hybrid peripheral claiming system.”).
65 See Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17, 27 n.4 (1997) (“[T]he abandonment of
‘central’ claiming [in American patent law] may be overstated.”); Fromer, supra note 64, at 735–41 (describing
“vestiges” of central claiming in the modern Patent Act).
66 See Warner-Jenkinson, 520 U.S. at 39–40; Graver Tank & Mfg. Co. v. Linde Co., 339 U.S. 605, 608–09 (1950)
(laying out factors to consider in determining equivalence).

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A potential danger of a peripheral claiming system is that patentees may seek to claim more than
they invented by couching the patent claims in broad, functional language—that is, by claiming a
result or goal without limitation to any specific structure or device that accomplishes the result.67
In Halliburton Oil Well Cementing Co. v. Walker, the Supreme Court limited this practice,
invalidating as indefinite a “functional” patent claim, in which the invention—an apparatus for
determining the location of an obstruction in an oil well—was claimed not in terms of specific
machinery, but instead as a “means for” performing various functions.68
Functional claims (also known as “means-plus-function” claims) such as those in Halliburton
may be convenient for the patentee, who can express a claim element in terms of a general end,
rather than an “exhaustive list” of every possible apparatus that could be used to perform that
goal.69 On the other hand, as Halliburton recognized, functional claims may be overbroad and
ambiguous, or permit the patentee to claim more than he actually invented.70 In the Patent Act of
1952, Congress enacted current Section 112(f) as a compromise for functional claims, overruling
Halliburton71 but providing a standard to make functional claims more definite.72
Under Section 112(f), a patentee may opt to express a claim element as “a means or step for
performing a specified function without the recital of structure, material, or acts in support
thereof.”73 If the patentee chooses to claim functionally, however, the claim is construed not to
cover all possible means of performing the function, but only “the corresponding structure,
material, or acts described in the specification and equivalents thereof.”74 Courts have held that a
patentee is presumed to invoke Section 112(f) when the term “means” is used in the claims.75
Conversely, there is a presumption that the patentee does not invoke Section 112(f) if she does not
use the term “means,” but that presumption may be overcome, such that Section 112(f) will apply
to any claim that fails to recite a “sufficiently definite structure” for performing a function.76

Rights of Patent Holders
With some exceptions, a patent is generally granted “for a term beginning on the date on which
the patent issues and ending 20 years from the date on which the application for the patent was

67 See Lemley, supra note 64, at 911–13. Such claiming should in theory be prohibited on novelty or enablement

grounds, see 35 U.S.C. §§ 102, 112(a), but the problem persists, for example, in modern software patents. See Lemley,
supra note 64, at 921–23 (citing examples).
68 See 329 U.S. 1, 8–9, 12–13 (1946).
69
Stephen Winslow, Means for Improving Modern Functional Patent Claiming, 98 GEO. L.J. 1891, 1892 (2010) (“A
patent can be clearer, more concise, and more comprehensible when the patentee drafts her claims using language
describing what a particular element does, rather than giving an exhaustive list of the various structures that could
provide that function within her invention.”).
70 See Halliburton, 329 U.S. at 12.
71 See Williamson v. Citrix Online, LLC, 792 F.3d 1339, 1347 (Fed. Cir. 2015) (en banc) (“In enacting [§ 112(f)],
Congress struck a balance in allowing patentees to express a claim limitation by reciting a function to be performed
rather than by reciting structure for performing that function, while placing specific constraints on how such a
limitation is to be construed . . . .”); P.J. FEDERICO, COMMENTARY ON THE NEW PATENT ACT (West 1954), reprinted in
75 J. PAT. & TRADEMARK OFF. SOC’Y 161, 186 (1993) (observing that “[t]he last paragraph of section 112” means that
“decisions such as that in [Halliburton Oil] are modified or rendered obsolete . . . .”).
72 Valmont Indus. v. Reinke Mfg. Co., 983 F.2d 1039, 1042 (Fed. Cir. 1993).
73 35 U.S.C. § 112(f).
74
Id. (emphasis added).
75 Williamson, 792 F.3d at 1348 (quoting Watts v. XL Sys., Inc., 232 F.3d 877, 880 (Fed. Cir. 2000)).
76 Id.

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filed.”77 The Patent Act includes provisions that may modify the 20-year term, including to
account for excessive delays in patent examination at the USPTO,78 or delays associated with
obtaining marketing approval from other federal agencies.79
Once granted, a valid patent gives the patent holder the exclusive right to make, use, offer to sell,
sell, or import the invention in the United States until the patent expires.80 Any other person who
practices the invention (i.e., makes, uses, offers to sell, sells, or imports it) without permission
from the patent holder infringes the patent and may be liable for monetary damages and
injunctive relief if sued by the patentee.81 To obtain relief from infringement, the patentee must
generally sue in court.82 Patent law is an area of exclusive federal jurisdiction,83 and the
traditional forum for most patent disputes is federal district court.84 Although patent suits may be
filed in any district court across the country with jurisdiction over the defendant and proper
venue,85 a single specialized court, the U.S. Court of Appeals for the Federal Circuit (Federal
Circuit), hears all appeals in patent cases.86

Defending Against Patent Suits
Parties accused of patent infringement may defend on several grounds. First, the accused
infringer may claim an “absence of liability” because of noninfringement.87 In other words, even
presuming the patent is valid, the patentee may fail to prove that the activities of the accused
infringer fall within the scope of the patent claims—that is, the accused infringer is not making,
using, selling, or importing the patented invention.88 Second, although patents benefit from a
77 35 U.S.C. § 154(a).
78 Id. § 154(b)(1).
79 Id. § 156. In the pharmaceutical context, patents claiming a drug product or medical device (or a method of using or

manufacturing the same) may be extended for up to five years to account for delays in obtaining regulatory approval, if
certain statutory conditions are met. See Eli Lilly & Co. v. Medtronic, Inc., 496 U.S. 661, 670–71 (1990); Merck & Co.
v. Hi-Tech Pharmacal Co., 482 F.3d 1317, 1320–21 (Fed. Cir. 2007); Stephanie Plamondon Bair, Adjustments,
Extensions, Disclaimers, and Continuations: When Do Patent Term Adjustments Make Sense?, 41 CAP. U. L. REV. 445,
460 (2013).
80 35 U.S.C. § 271(a).
81 Id. §§ 271, 281, 283–85.
82 35 U.S.C. § 281.
83 28 U.S.C. § 1338.
84 In 2023, roughly 3,108 patent lawsuits were filed in federal district courts, as compared to 1,192 petitions filed
before the Patent Trial and Appeal Board (PTAB). See 2023 Patent Dispute Report: Year in Review, UNIFIED PATENTS
(Jan. 8, 2024), https://www.unifiedpatents.com/insights/2024/1/8/patent-dispute-report-2023-in-review. The third main
forum for patent disputes is the International Trade Commission (ITC), which has authority to conduct administrative
trials (called “Section 337 investigations”) into whether imported goods violate patent and other intellectual property
rights. See 19 U.S.C. § 1337. The ITC usually receives fewer than 100 complaints per year (and not all of these are
patent cases). See Section 337 Statistics: Number of New, Completed, and Active Investigations by Fiscal Year
(Updated Quarterly), ITC,
https://www.usitc.gov/intellectual_property/337_statistics_number_new_completed_and_active.htm (last updated Feb.
3, 2025).
85 See generally TC Heartland LLC v. Kraft Foods Grp., 137 S. Ct. 1514, 1518–21 (2017) (addressing scope of patent
venue statute); Gunn v. Minton, 568 U.S. 251 (2013) (addressing scope of federal patent subject matter jurisdiction);
Xilinx, Inc. v. Papst Licensing GmbH & Co. KG, 848 F.3d 1346 (Fed. Cir. 2017) (addressing personal jurisdiction in
patent dispute).
86 28 U.S.C. § 1295(a)(1).
87 35 U.S.C. § 282(b)(1).
88 To prove direct infringement, the plaintiff must show that each element contained in a patent claim is practiced by
(continued...)

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presumption of validity, the accused infringer may assert that the patent is invalid.89 To prove
invalidity, the accused infringer must show, by clear and convincing evidence, that the USPTO
should not have granted the patent because it failed to meet the requirements for patentability.90
Thus, for example, the accused infringer may argue that the invention lacks novelty, is obvious, or
claims nonpatentable subject matter; that the patent fails to enable the invention; or that the patent
claims are indefinite.91 Finally, the accused infringer may assert as a defense that the patent is
unenforceable based on the inequitable or illegal activities of the patent holder, such as obtaining
the patent through fraud on the USPTO.92 While the patent holders bears the burden of proving
infringement,93 the accused infringer bears the burden of proving invalidity or inequitable
conduct.94
Following the passage of the 2011 Leahy-Smith America Invents Act (AIA),95 the Patent Trial
and Appeal Board (PTAB) has become an increasingly important forum for patent disputes.96 The
AIA created several new administrative procedures for challenging patent validity, including (1)
post-grant review (PGR), which allows any person to challenge patent validity based on any of
the requirements of patentability if the PGR petition is filed within nine months of the patent’s
issuance;97 (2) inter partes review (IPR), which allows any person other than the patentee to
challenge patent validity on limited grounds (novelty or obviousness based on prior patents or
printed publications) at any time more than nine months following the patent’s issuance;98 and (3)
a transitional program for covered business method patents (CBM), a PGR-like process limited to
certain patents claiming “business methods” that was available only through September 2020.99
Of these procedures, IPR is by far the most widely used.100 IPRs can only be used to seek
cancellation of patents based on a lack of novelty or nonobviousness, and not on Section 101
grounds (i.e., claiming ineligible subject matter).101

the alleged infringer, either literally or by an equivalent. Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S.
17, 29–30 (1997). Often, whether or not the accused infringer’s activities fall within the patent claims depends upon
claim construction: how the words used in the patent claims are interpreted. See generally Markman v. Westview
Instruments, Inc., 517 U.S. 370, 372–74 (1996); Phillips v. AWH Corp., 415 F.3d 1303, 1312–19 (Fed. Cir. 2005) (en
banc).
89 35 U.S.C. § 282(a), (b)(2)–(3).
90 Id. § 282(b)(2)–(3); Microsoft Corp. v. i4i Ltd. P’ship, 564 U.S. 91, 95–96 (2011).
91 See supra “Requirements for Patentability.”
92 35 U.S.C. § 282(b)(1); Therasense, Inc. v. Becton, Dickinson & Co., 649 F.3d 1276, 1285, 1290–91 (Fed. Cir. 2011)
(en banc).
93 Medtronic, Inc. v. Mirowski Fam. Ventures, LLC, 571 U.S. 191, 193 (2014).
94 35 U.S.C. § 282(a); Therasense, 649 F.3d at 1291.
95 Pub. L. No. 112-29, 125 Stat. 284 (2011).
96 See generally CRS Report R48016, The Patent Trial and Appeal Board and Inter Partes Review, by Christopher T.
Zirpoli and Kevin J. Hickey (2024); Rochelle Cooper Dreyfuss, Giving the Federal Circuit a Run for Its Money:
Challenging Patents in the PTAB, 91 NOTRE DAME L. REV. 235, 249 (2015).
97 35 U.S.C. §§ 321–329.
98 Id. §§ 311–319.
99 Pub. L. No. 112-29, § 18, 125 Stat 284, 329–30 (2011) (not codified in U.S.C.).
100 See PTAB Trial Statistics: FY23 End of Year Outcome Roundup, USPTO,
https://www.uspto.gov/sites/default/files/documents/ptab_aia_fy2023__roundup.pdf (last visited Mar. 6, 2025), at 3
(98% of petitions filed with PTAB in FY2023 were IPRs).
101 35 U.S.C. § 311(b).

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The Law of Section 101
At a general level, there are two basic requirements for an invention to claim patent-eligible
subject matter. First, the invention must fit into one or more of the four statutory categories in
Section 101—the claimed invention must be a (1) process, (2) machine, (3) manufacture, or (4)
composition of matter.102 Given the (intentionally) expansive nature of these terms, nearly all
claimed inventions will satisfy this requirement.103 Still, exceptions to this rule do exist. For
example, in In re Nuijten, the Federal Circuit held that a transitory electromagnetic signal was
neither a process, machine, manufacture, or composition of matter, and was therefore not patenteligible subject matter.104
Because most claimed inventions fit into one of the four statutory categories, the second
requirement tends to be more practically important, and receives more attention.105 The second
patentable subject matter requirement is that the invention cannot claim one of the judicially
created categories of ineligible subject matter. That is, the claimed invention must not be a (1) law
of nature, (2) natural phenomenon, or (3) abstract idea.106 As explained below, the modern
Supreme Court has articulated a two-step test for this second requirement, known as the
Alice/Mayo framework.107
The Supreme Court has justified the three ineligible categories as necessary to prevent patent
monopolies on the “‘basic tools of scientific and technological work,’” which “might tend to
impede innovation more than it would tend to promote it.”108 Thus, the Court has explained that
“a new mineral discovered in the earth or a new plant found in the wild is not patentable subject
matter. Likewise, Einstein could not patent his celebrated law that E=mc2; nor could Newton have
102 35 U.S.C. § 101.
103 See Lemley et al., supra note 21, at 1328 (“[P]atent claims almost never fall outside of the four fundamental

categories of § 101 . . . .”).
104 500 F.3d 1346, 1354–57 (Fed. Cir. 2007).
105 See Kevin Emerson Collins, Patent-Ineligibility As Counteraction, 94 WASH. U. L. REV. 955, 968 (2017)
(“Contemporary debates over patent-ineligibility rarely parse the plain meanings of [the four statutory categories].
They focus instead on a set of judicial exclusions from patent-eligibility that are not expressly codified in the statute:
laws of nature, products of nature, and abstract ideas . . . .”).
106 Diamond v. Diehr, 450 U.S. 175, 185 (1981). Diehr’s modern distillation of patentable subject matter doctrine to
these three categories is a somewhat simplified version of the doctrine’s historical development, which often identified
patent-ineligible categories in addition to these three. See, e.g., Daniel J. Klein, The Integrity of Section 101: A ‘New
and Useful’ Test for Patentable Subject Matter, 93 J. PAT. & TRADEMARK OFF. SOC’Y 287, 288 (2011) (listing eight
terms that the Court has used to denote patent-ineligible subject matter); Michel, supra note 20, at 1757 (counting six
categories of patent-ineligible subject matter); accord Emily Michiko Morris, Intuitive Patenting, 66 S.C. L. REV. 61,
66 n.31 (2014) (describing the Supreme Court’s patentable subject matter jurisprudence as “insolubly murky”).
In addition to the three modern patent-ineligible categories and their close variants (such as “products of nature” or
“physical phenomena” as synonyms for natural phenomena, see Diamond v. Chakrabarty, 447 U.S. 303, 309, 313
(1980), or “scientific truth” as a synonym for a law of nature, see Mackay Radio & Tel. Co. v. Radio Corp. of Am., 306
U.S. 86, 94 (1939)), courts have at times referenced “principles,” “natural agencies,” “functions of a machine,” “effects
of a machine,” “mathematical formulas,” “algorithms,” “mental processes,” “mental steps,” and “printed matter” as
patent-ineligible categories. See Le Roy v. Tatham, 55 U.S. 156, 175 (1852) (“principle[s]” and “natural agencies”);
Corning v. Burden, 56 U.S. 252, 268 (1853) (“function or abstract effect of a machine”); Gottschalk v. Benson, 409
U.S. 63, 67, 72 (1972) (“mathematical formula,” “algorithm,” “mental processes”); Diamond v. Diehr, 450 U.S. 175,
195–200 (1981) (Stevens, J., dissenting) (reviewing history of “mental steps” doctrine that prohibited patents on
“processes involving mental operations”); Praxair Distribution, Inc. v. Mallinckrodt Hosp. Prod. IP Ltd., 890 F.3d
1024, 1031–33 (Fed. Cir. 2018) (“printed matter”).
107 See infra “The Modern Alice/Mayo Framework.”
108 Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 71 (2012) (quoting Gottschalk v. Benson, 409
U.S. 63, 67 (1972)).

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patented the law of gravity.”109 At the same time, the Court has said that even if a mathematical
formula or law of nature is not patentable “in the abstract,” a practical application of such a
principle or law “to a new and useful end” is patent-eligible.110
Beyond such broad illustrations, it is not easy to define what an “abstract idea,” “law of nature,”
or “natural phenomenon” is.111 Because these exceptions to patent-eligible subject matter are
judicially created, they have no formal statutory definition; their meaning has instead been
developed through two centuries of case-by-case “common law” adjudication in the federal
courts.112 As a result, the scope of patentable subject matter has waxed and waned over time,
depending on the trends in judicial decisions.113
This section overviews the leading Supreme Court cases addressing patent-eligible subject matter,
beginning with formative cases from the 19th century and culminating in the series of 2010s
Supreme Court decisions that have led some to call for legislative reform of Section 101.114

Historical Development of the Judicial Exceptions to
Patent-Eligible Subject Matter
Nineteenth Century
The 1853 case of Le Roy v. Tatham, the “fountainhead” of American patentable subject matter
jurisprudence,115 concerned a patent on machinery to manufacture metal pipes that exploited a
109 Diamond v. Chakrabarty, 447 U.S. 303, 309 (1980).
110 See, e.g., Diehr, 450 U.S. at 187; Funk Bros. Seed Co. v. Kalo Inoculant Co., 333 U.S. 127, 130 (1948); Mackay

Radio & Telegraph Co. v. Radio of Am., 306 U.S. 86, 94 (1939); Le Roy, 55 U.S. at 174–75.
111 See Morris, supra note 106, at 62 (describing the Supreme Court’s patentable subject matter jurisprudence as
“insolubly murky”); Klein, supra note 106, at 289 (describing the three categories of nonpatentable subject matter as
“metaphysically vague and extra-statutory”); Funk Bros., 333 U.S. at 134–35 (Frankfurter, J., concurring) (“It only
confuses the issue, however, to introduce such terms as ‘the work of nature’ and the ‘laws of nature.’ For these are
vague and malleable terms infected with too much ambiguity and equivocation. Everything that happens may be
deemed ‘the work of nature,’ and any patentable composite exemplifies in its properties ‘the laws of nature.’”).
112 See, e.g., Peter S. Menell, Forty Years of Wondering in the Wilderness and No Closer to the Promised Land:
Bilski’s Superficial Textualism and the Missed Opportunity to Return Patent Law to Its Technology Mooring, 63 STAN.
L. REV. 1289, 1307 (2011) (“Since the founding of our nation, courts have evolved [patentable subject matter limits]
within a hybrid constitutional/common law tradition.”); Lemley et al., supra note 21, at 1325 (describing the three
judicially created ineligible categories as “common law exceptions” to patentable subject matter).
113 The evolving standards applied to the patentability of computer software over the last 50 years are just one notable
example. See generally Lemley et al., supra note 21, at 1317–19 (reviewing the “tortured history” of the patentability
of software). Compare, e.g., Benson, 409 U.S. 63 (method for converting binary-coded decimal numerals into pure
binary numerals on computer is not patentable subject matter) with State Street Bank v. Signature Fin. Grp., 149 F.3d
1368, 1373 (Fed. Cir. 1998) (Rich, J.) (transformations of data are patentable so long as they produce “a useful,
concrete and tangible result”), abrogated by In re Bilski, 545 F.3d 943, 960 (Fed. Cir. 2008) (en banc) and Alice Corp.
Pty. v. CLS Bank Int’l, 573 U.S. 208, 224–26 (2014) (computer-implemented business method not patentable because
it is an abstract idea lacking an “inventive concept”). For a broader review of the history of patentable subject matter
jurisprudence, see, e.g., Jeffrey A. Lefstin, Inventive Application: A History, 67 FLA. L. REV. 565, 570–645 (2015);
Max Stul Oppenheimer, Patents 101: Patentable Subject Matter and Separation of Powers, 15 VAND. J. ENT. & TECH.
L. 1, 5–28 (2012); Joshua D. Sarnoff, Patent-Eligible Inventions After Bilski: History and Theory, 63 HASTINGS L.J.
53, 63–90 (2011); John F. Duffy, Rules and Standards on the Forefront of Patentability, 51 WM. & MARY L. REV. 609,
623–46 (2009).
114 See infra Table 1.
115 See, e.g., Lefstin, supra note 113, at 594 (describing Le Roy as “the fountainhead of subject-matter exclusion in
American patent law”); Menell, supra note 112, at 1296 (describing Le Roy as “the foundation for much patentable
subject matter jurisprudence”).

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newly developed property of lead.116 Although the Court ultimately did not decide the case on
subject matter grounds,117 Le Roy relied on influential English patent cases118 to set forth a basic
distinction between abstract “principles” and natural laws (which may not be patented) and
practical applications of those principles (which may be patented).119 The Court stated that “[a]
principle, in the abstract, is a fundamental truth; an original cause; a motive; these cannot be
patented, as no one can claim in either of them an exclusive right.”120 On the other hand, a “new
property discovered in matter, when practically applied, in the construction of a useful article of
commerce or manufacture, is patentable,” for the “invention is not in discovering [the natural
principles], but in applying them to useful objects.”121
In its next term, the Court applied this rule to Samuel Morse’s patent on the telegraph in the
famous case O’Reilly v. Morse.122 Although the Court found that Morse was the first inventor of
the telegraph and sustained much of his patent,123 the Court rejected Morse’s eighth claim to any
“use of the motive power of the electric or galvanic current . . . however developed for marking
or printing intelligible characters, signs, or letters, at any distances, being a new application of
that power of which I claim to be the first inventor or discoverer.”124 Observing that “the
discovery of a principle in natural philosophy or physical science, is not patentable,”125 Chief
Justice Roger Taney’s majority opinion held that Morse’s eighth claim was “too broad” because
he had not discovered “that the electric or galvanic current will always print at a distance, no
matter what may be the form of the machinery” used, but only that the specific machinery
disclosed in the patent specification would do so.126
In the second half of the 19th century, the Court issued a series of important decisions on the
patentability of processes. The result of these cases was a move away from an earlier rule that
prohibited “pure” method patents as ineligible (i.e., a process claimed independently of the
specific machinery used to accomplish the method) either by construing nominal process patents
as claiming a machine or limiting the process patents to the machinery disclosed and its
equivalents.127 In Cochrane v. Deener, which involved a patent on an improved manufacturing
process for flour, the Court defined a patentable process as “a mode of treatment of certain
materials to produce a given result. It is an act, or a series of acts, performed upon the subjectmatter to be transformed and reduced to a different state or thing.”128 Cochrane held that such
116 55 U.S. (14 How.) 156, 176–77 (1853).
117 The dispositive issue in the case was the scope of the patent claims. See infra note 181; Lefstin, supra note 113, at

595 (“The outcome in Le Roy therefore turned entirely on the Court’s narrow construction of the claim.”).
118 For a full historical account of these English cases and how they shaped the Supreme Court’s jurisprudence, see
Lefstin, supra note 113, at 577–644.
119 Le Roy, 55 U.S. at 174–75.
120 Id. at 175.
121 Id.
122 56 U.S. 62 (1853).
123 Id. at 111–12, 123–24.
124 Id. at 112–20.
125 Id. at 116.
126 Id. at 117, 119.
127 See, e.g., Corning v. Burden, 56 U.S. (15 How.) 252, 268–70 (1853) (construing “equivocal” patent to claim a
machine, and not a process, to save its validity because a “process” in the sense of “the function of a machine, or the
effect produced by it” cannot be patented); see generally Sarnoff, supra note 113, at 67 (“[A]t the end of the eighteenth
century, pure method patents—methods claiming all future applications and not merely those substantially similar to
the disclosed implementing machinery and their equivalents—were ineligible for protection and remained so until the
late nineteenth century.”) & id. n. 88 (collecting cases).
128 94 U.S. 780, 788 (1876).

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methods are patentable “irrespective of the particular form of the instrumentalities used.”129
Similarly, in Tilghman v. Proctor, the Court held that a method for separating fat into glycerin and
fatty acids using water, pressure, and heat was patentable.130
In The Telephone Cases, the Court distinguished Morse to allow Alexander Graham Bell’s patent
claim on a “method of and apparatus for transmitting vocal or other sounds telegraphically, as
herein described, by causing electrical undulations, similar in form to the vibrations of the air
accompanying the said vocal or other sounds, substantially as set forth.”131 Chief Justice Edward
Douglass White interpreted Morse as holding that “the use of magnetism as a motive power,
without regard to the particular process with which it was connected in the patent, could not be
claimed, but that its use in that connection could.”132 The Court found that Bell’s claim, unlike
Morse’s, did not reach uses of electricity to transmit speech that are “distinct from the particular
process with which it is connected in [Bell’s] patent,” and upheld the claim, so construed.133

Twentieth Century
In the first half of the 20th century, the Court decided two major cases on the patentability of
natural phenomena. In American Fruit Growers v. Brogdex Co., the Court rejected patent claims
on citrus fruit treated with a solution of borax to render it resistant to mold.134 The Court held that
treated fruit was not a “manufacture” under Section 101, but a patent-ineligible “natural article”;
treatment with borax did not effect a “change in the name, appearance, or general character of the
fruit” or imbue it with a “new or distinctive form, quality, or property.”135 In Funk Brothers Seed
Co. v. Kalo Inoculant Co., the Court rejected patent claims on an inoculant for leguminous plants
consisting of multiple species of bacteria, where the particular bacterial strains were selected to
avoid inhibiting each other (as prior multispecies combinations had).136 Because the patentee’s
combination “produces no new bacteria [and] no change in the six species of bacteria,” Justice
William Douglas’s majority opinion held that it was only “the discovery of some of the
handiwork of nature and hence is not patentable.”137
From 1972 to 1981, the Supreme Court decided four patentable subject matter cases.138 In
Gottschalk v. Benson, the Court held that an algorithm for converting binary-coded decimal
numerals into pure binary numerals (either by hand, or, more practically, on a computer) was
patent-ineligible.139 Justice Douglas reasoned that “one may not patent an idea” and that
upholding this patent would “wholly pre-empt the mathematical formula and in practical effect
would be a patent on the algorithm itself.”140 Second, in Parker v. Flook, the Court rejected a
129 Id. at 787.
130 102 U.S. 707, 728–30 (1880).
131 Dolbear v. Am. Bell Tel. Co. (The Telephone Cases), 126 U.S. 1, 531, 534–35 (1888).
132 Id. at 534.
133 Id. at 534–35.
134 283 U.S. 1, 6, 11–12 (1931).
135 Id. at 11–12.
136 333 U.S. 127, 130–32 (1948).
137 Id.
138 Three of these four (Benson, Flook, and Diehr), which concern the patentability of inventions relating to

mathematical formulas and computers, are often referred to as a “trilogy.” See, e.g., Michel, supra note 20, at 1755;
Menell, supra note 112, at 1290. This usage leaves out Chakrabarty, which was also decided in the same time frame,
because that case concerned the exception for products of nature.
139 409 U.S. 63, 64, 71–73 (1972).
140 Id. at 71–72.

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patent on a method for updating alarm limits during catalytic conversion of hydrocarbons (such as
petroleum), which relied in part on a mathematical formula, because the only novel feature of the
method was the mathematical formula.141 Third, in Diamond v. Chakrabarty, the Court upheld a
patent on a genetically engineered bacterium useful in breaking down oil (e.g., in cleaning up oil
spills).142 Chief Justice Warren Burger distinguished American Fruit Growers and Funk Brothers
because this bacterium, although a living organism, was human-made and possessed “markedly
different characteristics from any [bacteria] found in nature.”143 Finally, in Diamond v. Diehr, the
Court distinguished Flook to uphold a patent on a process for molding synthetic rubber that relied
on a mathematical formula (the Arrhenius equation).144 Justice William Rehnquist’s majority
opinion reached back to Cochrane v. Deener, holding that the process at issue was patentable
because it transformed an article (uncured rubber) into a different state or thing.145 Even though
the method used a mathematical formula, the patent in Diehr did not claim the formula itself and
would not “pre-empt the use of that equation” in other fields.146
After Diehr, the Court did not decide a major patentable subject matter case for nearly 30
years.147 Development of patent-eligible subject matter law was mainly left to the Federal Circuit,
whose decisions generally expanded patent-eligible subject matter,148 such that by the late 1990s
Section 101 became perceived as “a dead letter.”149

141 437 U.S. 584, 585, 591–92 (1978).
142 447 U.S. 303, 305, 309–10 (1980).
143 Id. at 310.
144 450 U.S. 175, 177, 183–93 (1981).
145 Id. at 184.
146 Id. at 187. In the view of many commentators, Diehr effectively overturned Flook (or at least some statements in

Flook) without explicitly saying so. See, e.g., Michel, supra note 20, at 1756 (“Diehr, to my eye, overruled Flook five
to four.”); Menell, supra note 112, at 1298 (“Justice Rehnquist [in Diehr] effectively overrode Flook’s statutory subject
matter test.”); BCLT Report, supra note 16, at 554 (“Flook was effectively overruled three years later in Diamond v.
Diehr . . . .”); Athena Diagnostics, Inc. v. Mayo Collaborative Servs., 927 F.3d 1333, 1346 (Fed. Cir. 2019) (Chen, J.,
concurring in the denial of rehearing en banc) (“Given Diehr’s evident disagreement with Flook’s analysis, Diehr, as
the later opinion, was widely understood to be the guiding, settled precedent on § 101 for three decades.”); Dennis
Crouch, Revival of Parker v. Flook II, PATENTLYO (Jan. 4, 2018), https://patentlyo.com/patent/2018/01/revival-parkerflook.html (presenting data showing that courts rarely cited Flook between 1982 and 2007).
The Supreme Court does not appear to view matters this way, however—it continues to cite and rely on Flook as good
law. See, e.g., Alice Corp. Pty. v. CLS Bank Int’l, 573 U.S. 208, 218, 222 (2014).
147 See Lemley et al., supra note 21, at 1317; Menell, supra note 112, at 1298. There are two partial exceptions to this
generalization. The first is J.E.M. Ag Supply, Inc. v. Pioneer Hi-Bred Int’l, Inc., in which the Court held that humanmade plant varieties were patentable under Section 101. 534 U.S. 124, 127 (2001). However, that case turned not on
general patent-eligibility principles, but on whether two specialized statutes for protection of plant varieties precluded
utility patents on plants under the general provisions of Section 101. Id. at 132–44. Second, although the Supreme
Court ultimately did not decide the case, Justice Breyer’s 2006 dissent from the dismissal of a writ of certiorari as
improvidently granted in Laboratory Corporation of America Holdings v. Metabolite Laboratories, Inc., served as an
important signal of the Court’s renewed interest in patentable subject matter. See 548 U.S. 124 (2006). Metabolite
involved claims for diagnosing vitamin deficiencies, much like the claims the Supreme Court would address years later
in Mayo, when the Court largely adopted the reasoning of Justice Breyer’s Metabolite dissent. See id. at 129, 135–38.
148 See generally Menell, supra note 112, at 1298–99; Julie E. Cohen & Mark A. Lemley, Patent Scope and Innovation
in the Software Industry, 89 CAL. L. REV. 1, 9–14 (2001). The canonical examples are In re Alappat, 33 F.3d 1526,
1542–45 (Fed. Cir. 1994) (en banc) (permitting software claims if tied to a machine, including a programmed generalpurpose computer) and State Street Bank v. Signature Financial Group, 149 F.3d 1368, 1373 (Fed. Cir. 1998) (Rich, J.)
(holding that computer-implemented business methods are patentable if tied to a machine that produces “a useful,
concrete and tangible result”). Both cases were later abrogated. See In re Bilski, 545 F.3d 943, 959–60 (Fed. Cir. 2008)
(en banc), aff’d, sub nom. Bilski v. Kappos, 561 U.S. 593 (2010).
149 Lemley et al., supra note 21, at 1318 (“[A]fter 1998, patentable subject matter was effectively a dead letter”).

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The Modern Alice/Mayo Framework
In 2010, the Supreme Court reentered the field of patent-eligible subject matter, deciding four
cases on the issue within five years.150 These cases established the two-step Alice/Mayo test for
patentable subject matter.
The first step of the Alice/Mayo test addresses whether the patent claims are “directed to” an
ineligible concept: a law of nature, a natural phenomenon, or an abstract idea.151 The inquiry at
step one focuses on the “claim as whole.”152 To be “directed to” an eligible concept at step one of
Alice/Mayo, the claims must not simply involve a patent-ineligible concept.153 Rather, the “focus
of the claims” must be a patent-ineligible concept, and not the improvement of a technological
process.154 If the patent claims are not directed to an ineligible concept, then the subject matter is
patent-eligible.155
If the claims are directed to an ineligible category, then the invention is not patentable unless the
patent claims have an “inventive concept” under the second step of the Alice/Mayo test.156 Step
two of Alice/Mayo considers the elements of each patent claim both individually and as an
ordered combination in the search for an “inventive concept”—additional elements that
“transform the nature of the claim” into a patent-eligible application of an ineligible concept.157
To have an “inventive concept,” the patent claims must contain elements “sufficient to ensure that
the patent in practice amounts to significantly more than a patent upon the [ineligible concept]
itself.”158 Claim limitations that are “conventional, routine and well understood,” such as generic
computer implementation, cannot supply an inventive concept.159
Bilski v. Kappos, the first in the series of Supreme Court cases that developed what became
known as the Alice/Mayo framework, concerned a patent on a business method for hedging
against price-fluctuation risks in energy and commodity markets.160 The Federal Circuit had held
that this method was not patentable as a “process” under Section 101 because it failed the
“machine-or-transformation test”—that is, it was neither “tied to a particular machine or
apparatus” nor “transform[ed] a particular article into a different state or thing.”161 All nine
members of the Supreme Court agreed with that result—that the business method at issue was not
150 Bilski v. Kappos, 561 U.S. 593 (2010); Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66 (2012);

Ass’n for Molecular Pathology v. Myriad Genetics, Inc., 569 U.S. 576 (2013); Alice Corp. Pty. v. CLS Bank Int’l, 573
U.S. 208 (2014).
151 Alice, 573 U.S. at 217.
152 Athena Diagnostics, Inc. v. Mayo Collaborative Servs., 915 F.3d 743, 750 (Fed. Cir. 2019) (citing Elec. Power Grp.,
v. Alstom S.A., 830 F.3d 1350, 1353 (Fed. Cir. 2016)).
153 Enfish, LLC v. Microsoft Corp., 822 F.3d 1327, 1335–36 (Fed. Cir. 2016).
154 Id.; see also Athena, 915 F.3d at 750 (“To determine whether a claim is directed to an ineligible concept, we have
frequently considered whether the claimed advance improves upon a technological process or merely an ineligible
concept, based on both the written description and the claim.”) (citations omitted).
155 Alice, 573 U.S. at 217.
156 Id.
157 Alice, 573 U.S. at 217–28 (quotations omitted).
158 Id. (quoting Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 73 (2012)).
159 Ariosa Diagnostics, Inc. v. Sequenom, Inc., 788 F.3d 1371, 1378 (Fed. Cir. 2015); accord Alice, 573 U.S. at 225;
Mayo, 566 U.S. at 79 (“Purely ‘conventional or obvious’ ‘[pre]-solution activity’ is normally not sufficient to transform
an unpatentable law of nature into a patent-eligible application of such a law.” (quoting Parker v. Flook, 437 U.S. 584,
590 (1978))).
160 Bilski, 561 U.S. at 598–99.
161 In re Bilski, 545 F.3d 943, 954 (Fed. Cir. 2008) (en banc) (Michel, C.J.).

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patent-eligible—but differed significantly as to their reasoning. Writing for five Justices, Justice
Anthony Kennedy held that the machine-or-transformation test was not the “sole test” for
determining whether a process is patent-eligible but still “a useful and important clue.”162 While
the majority rejected the “atextual” notion that business methods were categorically unpatentable
under Section 101,163 it relied on Benson and Flook to conclude that this particular patent
attempted to claim an unpatentable abstract idea: the “concept of hedging risk.”164 Concurring
only in the judgment, Justice John Paul Stevens wrote for four Justices who would have held,
based on the history of the Patent Act and its constitutional purpose, that business methods were
always patent-ineligible.165
In Mayo Collaborative Services v. Prometheus Laboratories, the Court addressed the scope of the
“law of nature” exception.166 The patent in Mayo claimed a method for measuring metabolites in
human blood in order to calibrate the dosage of thiopurine drugs in the treatment of autoimmune
disorders.167 Writing for a unanimous Court, Justice Stephen Breyer’s opinion held that the patent
claims were addressed to a law of nature: “namely, relationships between concentrations of
certain metabolites in the blood and the likelihood that a dosage of a thiopurine drug will prove
ineffective or cause harm.”168 Because the claims were little “more than an instruction to doctors
to apply the applicable laws when treating their patients,” the patent lacked any inventive concept
and was held to be patent-ineligible.169
The next case, Association for Molecular Pathology v. Myriad Genetics, Inc., concerned the
applicability of the “natural phenomena” exception to the patentability of human DNA.170 The
inventor in Myriad had discovered the precise location and genetic sequence of two human genes
associated with an increased risk of breast cancer.171 Based on this discovery, the patentee claimed
two molecules associated with the genes: (1) an isolated DNA segment and (2) a complementary
DNA (cDNA) segment, in which the nucleotide sequences that do not code for amino acids were
removed in the laboratory.172 Justice Clarence Thomas’s unanimous opinion in Myriad held that
isolated DNA segments were nonpatentable products of nature because the patent claimed
naturally occurring genetic information.173 The Court held, however, that cDNA, as a synthetic
molecule distinct from naturally occurring DNA, was patentable even though the underlying
nucleotide sequence was dictated by nature.174
Most recently, Alice Corp. v. CLS Bank International examined the scope of the “abstract idea”
category of nonpatentable subject matter.175 Alice concerned a patent on a system for mitigating
162 Bilski, 561 U.S. at 604.
163 Id. at 609.
164 Id. at 609–12.
165 Id. at 626–57 (Stevens, J., concurring in the judgment).
166 566 U.S. 66, 77 (2012).
167 Id. at 73–75.
168 Id. at 77.
169 Id. at 79.
170 569 U.S. 576 (2013).
171 Id. at 579.
172 Id. at 580–85.
173 Id. at 591–94. Justice Antonin Scalia joined the opinion save for the “fine details of molecular biology,” as he found

himself “unable to affirm those details on my own knowledge or even my own belief.” Id. at 596 (Scalia, J., concurring
in part and in the judgment).
174 Id. at 594–95.
175 573 U.S. 208 (2014).

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“settlement risk”—the risk that only one party to a financial transaction will pay what it owes—
using a computer as an intermediary.176 The Court first held, relying on Bilski, that the invention
was directed at “the abstract idea of intermediated settlement.”177 Although this idea was
implemented on a computer (which is, of course, a physical machine), the patent lacked an
inventive concept because the claims merely “implement[ed] the abstract idea of intermediated
settlement on a generic computer.”178
Table 1 summarizes the facts and holding of the Supreme Court’s major patentable subject matter
cases, in reverse chronological order.
Table 1. Major Supreme Court Decisions on Patentable Subject Matter
Case Citation

Claimed Inventions

Holding and Rationale

Alice Corp. Pty. v. CLS
Bank Int'l, 573 U.S.
208 (2014)

Computer-implemented method and
system for mitigating settlement risk in
financial transactions using a third-party
intermediary

Ineligible: The claims are drawn to the
abstract idea of intermediated settlement;
implementation on a generic computer does
not transform an ineligible abstract idea into a
patent-eligible invention.

Ass'n for Molecular
Pathology v. Myriad
Genetics, Inc., 569
U.S. 576 (2013)

Isolated human DNA segments and
exon-only complementary DNA (cDNA)
segments corresponding to genes
discovered to be linked to an increased
risk of breast cancer

Certain Claims Ineligible: Isolated human
DNA segments are patent-ineligible because
the nucleotide sequence is a product of
nature and isolation from the rest of the
genome is insufficient to render them
patentable; however, cDNA is patentable
because it is not naturally occurring.

Mayo Collaborative
Servs. v. Prometheus
Labs., Inc., 566 U.S.
66 (2012)

Method for optimizing dosage of
thiopurine drugs for treating
autoimmune disease, by administering
the drug, measuring a metabolite, and
adjusting the dosage based on the
measurement

Ineligible: The relationship between the
concentration of particular metabolites in the
blood and a drug’s effectiveness is directed to
a law of nature, and the claims lack an
inventive concept beyond conventional postsolution activity.

Bilski v. Kappos, 561
U.S. 593 (2010)

Business method for hedging against
price-fluctuation risks in energy and
commodity markets

Ineligible: Although business methods are
not categorically patent-ineligible, the process
at issue was not patentable because it claimed
the abstract idea of hedging risk.

J.E.M. Ag. Supply v.
Pioneer Hi-Bred Int’l,
Inc., 534 U.S. 124
(2001)

Human-developed inbred and hybrid
corn plant varieties and seeds

Eligible: Newly developed plant varieties are
human-made manufactures or compositions
of matter, even though protection may also
be available under the Plant Patent Act or the
Plant Variety Protection Act.

Diamond v. Diehr, 450
U.S. 175 (1981)

Process for molding raw, uncured
synthetic rubber into cured products,
relying on the Arrhenius equation and a
programmed computer to calculate the
curing time

Eligible: The invention does not claim a
mathematical formula or a law of nature as
such, but applies a natural law to a particular
industrial process that transforms an article
into a different state or thing.

Diamond v.
Chakrabarty, 447 U.S.
303 (1980)

Genetically engineered bacterium
capable of breaking down components in
crude oil

Eligible: The genetically engineered
bacterium was not naturally occurring and
possessed markedly different characteristics
from any bacteria found in nature.

176

Id. at 212.

177 Id. at 221.
178 Id. at 225.

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Case Citation

Claimed Inventions

Holding and Rationale

Parker v. Flook, 437
U.S. 584 (1978)

Method of updating alarm limits used in
catalytic conversion of hydrocarbons
(e.g., in oil refining) relying on a
mathematical formula

Ineligible: The only novel feature of the
invention was a mathematical formula,
conventionally applied to a specific field.

Gottschalk v. Benson,
409 U.S. 63 (1972)

Method for converting binary-coded
decimal numerals into pure binary
numerals on digital computer

Ineligible: The patent claims cover all
practical uses of a mathematical algorithm and
would, in effect, amount to a patent on the
algorithm itself.

Funk Bros. Seed Co. v.
Kalo Inoculant Co.,
333 U.S. 127 (1948)

Inoculant for leguminous plants
comprising several strains of mutually
noninhibitive species of bacteria to
improve nitrogen fixation

Ineligible: Each bacterial strain is naturally
occurring, and discovery of the noninhibitive
qualities of certain strains was not invention
but merely the discovery of a nonpatentable
natural phenomenon.

Mackay Radio & Tel.
Co. v. Radio Corp. of
Am., 306 U.S. 86
(1939)179

Radio antenna in which the angle of the
wires and their length are determined by
a mathematical formula

Assumed to be patentable: Although a
mathematical expression of a scientific truth
is not patentable, a novel and useful structure
created with the aid of knowledge of scientific
truth may be patentable.

Am. Fruit Growers v.
Brogdex Co., 283 U.S.
1 (1931)

Citrus fruit treated with borax solution
to render it resistant to mold

Ineligible: Treatment with borax did not
transform the fruit (a product of nature) into
a manufacture with a new or distinctive form,
quality, or property.

The Telephone Cases,
126 U.S. 1 (1888)

Method and apparatus for transmitting
sound telegraphically by causing
electrical undulations, similar to air
vibrations accompanying speech and
other sounds

Eligible: The patentee did not claim all uses
of electricity to transmit speech at a distance,
but only the particular process and apparatus
disclosed in the patent.

Tilghman v. Proctor,
102 U.S. 707 (1881)

Process for separating fat into glycerin
and fatty acids using water, pressure, and
heat

Eligible: New and useful manufacturing
processes are “arts” that may be patented
independently of the apparatus used.

Cochrane v. Deener,
94 U.S. 780 (1877)

Improved industrial process for
manufacturing flour

Eligible: A process (“a series of acts,
performed upon the subject-matter to be
transformed and reduced to a different state
or thing”) is patentable independent of the
machinery used.

Rubber-Tip Pencil Co.
v. Howard, 87 U.S.
(20 Wall.) 498
(1874)

Rubber cap with cavity designed to be
attached to lead pencils for convenient
use as an eraser

Ineligible: An “idea of itself” (here, the idea
of attaching a piece of rubber to the end of a
pencil for use as an eraser) is not patentable.

Corning v. Burden, 56
U.S. (15 How.) 252
(1854)

Machine for rolling puddle balls and
other masses of iron used in the
manufacture of iron products

Eligible: The patentee did not claim the
function or abstract effect of a machine, but
only the machine that produced the result.

179 Although Mackay Radio is widely quoted in subsequent jurisprudence for the proposition that useful applications of

laws of nature are patentable, see, for example, Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 71
(2012); Diamond v. Diehr, 450 U.S. 175, 188 (1981), Justice Harlan Stone’s statement is dicta because the Court
merely “assume[d], without deciding” that the invention was patentable, ruling instead on grounds of noninfringement,
see Mackay Radio, 306 U.S. at 94, 101.

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Case Citation

Claimed Inventions

Holding and Rationale

O'Reilly v. Morse, 56
U.S. (15 How.) 62
(1854)180

Any use of electro-magnetism for
printing intelligible characters, signs, or
letters, at a distance

Ineligible: The discovery of a scientific
principle is not patentable, nor can a patentee
claim a useful result in the abstract, apart
from the particular process or machine by
which the result is accomplished.

Le Roy v. Tatham, 55
U.S. (14 How.) 156
(1853)181

Machinery for manufacturing wrought
metal pipes exploiting a newly
discovered property of lead

Potentially patentable: Although a
principle in the abstract is not patentable, a
practical application of such a principle to a
new and useful end is patentable.

Source: CRS.

The Debate Over Alice/Mayo and Section 101
Reform
A substantial group of patent law stakeholders, including inventors, academics, industry
representatives, patent attorneys, current and former Federal Circuit judges, and former USPTO
officials, has criticized the Alice/Mayo framework on various grounds.182 Other patent law
stakeholders defend the Supreme Court’s Section 101 decisions.183

Criticisms of the Alice/Mayo Framework
Generally, critics of the Court’s patentable subject matter jurisprudence raise four principal
concerns. First, the Alice/Mayo framework is criticized as excessively vague, subjective, and
unpredictable in application. For example, the Federal Circuit has stated that when determining
whether a patent claim is “directed to” an ineligible concept at step one, courts must determine
whether the “focus” of the claims is on that concept.184 At the same time, the Federal Circuit has
cautioned that this “focus” must be articulated “with enough specificity to ensure the step one

180 The specific doctrinal basis of O’Reilly v. Morse is unclear, as the Court speaks in language that, when cast in

modern terms, sounds at times like enablement and at times like patentable subject matter. Compare 56 U.S. at 113
(“The court is of opinion that the claim is too broad . . . .”) with id. at 116 (“[T]he discovery of a principle in natural
philosophy or physical science, is not patentable.”). Many patent scholars regard Morse as a case not about Section 101
but about enablement under Section 112 of the modern Patent Act. See, e.g., Taylor, supra note 20, at 205 (“In modern
terms, it is quite clear that the problem with Claim 8 in Morse’s patent was based on the enablement and written
description requirements located in § 112 and not in § 101.”); Lefstin, supra note 113, at 597 (“Morse is about
disclosure and scope, not patent-eligible subject matter.”). The Supreme Court, however, appears to regard Morse as
primarily a subject matter decision. See, e.g., Mayo, 566 U.S. at 70, 73 (citing to Morse to support notion that “laws of
nature” or claims that “preempt the use of a natural law” are “not patentable”).
181 Statements in Le Roy to the effect that a “principle, in the abstract” is not patentable, but a practical application of
such a principle may be patentable, 55 U.S. at 174–75, are widely quoted and influential in subsequent American
jurisprudence. See supra note 115. Nonetheless, because the result in Le Roy turned primarily on claim construction,
see 55 U.S. at 176, these general statements were dicta and did not entail the holding of the case.
182
See infra “Criticisms of the Alice/Mayo Framework.”
183 See infra “Defenses of the Alice/Mayo Framework.”
184 Elec. Power Grp. v. Alstom S.A., 830 F.3d 1350, 1353 (Fed. Cir. 2016).

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inquiry is meaningful.”185 The appropriate level of specificity can vary from patent to patent and
from judge to judge.186
Thus, in the view of many stakeholders, the Supreme Court’s patentable subject matter case law
and the Federal Circuit’s implementation of the Alice/Mayo framework fail to articulate
“objective, predictable criteria” for making patent-eligibility determinations.187 Key terms, such
as what an “abstract idea” is, or precisely how claim elements can make an invention
“significantly more” than an ineligible category (the “inventive concept”), are largely left
undefined, making it difficult for patent applicants and litigants to know whether their patent
claims will survive judicial scrutiny.188 Moreover, the Federal Circuit has explicitly recognized
that the two steps of the analysis are not clearly defined and may overlap.189 As a result, many
observers characterize the court’s Section 101 jurisprudence as a “highly subjective,” “I know it
when I see it” approach.190 This subjectivity, in the view of critics, injects unpredictability and
uncertainty into whether an invention is of a type that is patentable.191
Second, the Alice/Mayo framework is criticized as legally flawed on various grounds. Some
stakeholders argue that the Alice/Mayo framework misinterprets Section 101, imposing “extrastatutory” requirements for patent eligibility, contrary to congressional intent or the constitutional
purpose of patent law.192 Others argue that Mayo’s requirement of an “inventive concept” rests on
a historically inaccurate understanding of 19th century English patent law, first imported into
185 Thales Visionix Inc. v. United States, 850 F.3d 1343, 1347 (Fed. Cir. 2017).
186 See Visual Memory LLC v. NVIDIA Corp., 867 F.3d 1253, 1262 (Fed. Cir. 2017) (Hughes, J., dissenting)

(disagreeing with the majority over whether characterizing the claims as directed to “categorical data storage” views
the invention “at an unduly ‘high level of abstraction’”) (quoting Enfish, LLC v. Microsoft Corp., 822 F.3d 1327, 1337
(Fed. Cir. 2016)).
187
USPTO PSM REPORT, supra note 16, at 29.
188 See id. at 30 (describing comments that the Alice/Mayo test “fails to define crucial terms, such as ‘abstract’ and
‘substantially more’”); Taylor, supra note 20, at 231 (“[N]o one really knows what an inventive concept is.”); Lemley
et al., supra note 21, at 1316 (“[N]o one understands what makes an idea ‘abstract,’ and hence ineligible . . . .”);
Morris, supra note 106, at 68 (arguing that the judicially created patentable subject matter decisions are “merely post
hoc rationalizations”). Some Supreme Court Justices have echoed this criticism. See, e.g., Bilski v. Kappos, 561 U.S.
593, 621 (2010) (Stevens, J., concurring in the judgment) (“The Court . . . never provides a satisfying account of what
constitutes an unpatentable abstract idea.”); Fred Funk Seed Bros. Co. v. Kalo Inoculant Co., 333 U.S. 127, 134–35
(1948) (Frankfurter, J., concurring) (“It only confuses the issue, however, to introduce such terms as ‘the work of
nature’ and the ‘laws of nature.’ For these are vague and malleable terms infected with too much ambiguity and
equivocation.”). To some extent, uncertainty in Section 101 is not a new phenomenon. See, e.g., Duffy, supra note 113,
at 623–38 (reviewing history of failed patentable subject matter rules and observing that “instability in the law of
patentable subject matter” is a recurring issue). However, at least in the decade before Mayo, uncertainty was less
practically important for patentees because courts and the USPTO only “rarely” rejected patents based on Section 101.
See BCLT Report, supra note 16, at 575–76 (reviewing data showing a “dramatic” increase in the number of Section
101 district court decisions following Mayo, with a “10-fold” increase following Alice).
189 Elec. Power Grp., 830 F.3d at 1353 (“[T]he two stages are plainly related: not only do many of our opinions make
clear that the two stages involve overlapping scrutiny of the content of the claims, but we have noted that there can be
close questions about when the inquiry should proceed from the first stage to the second.”) (citations omitted).
190 See, e.g., USPTO PSM REPORT, supra note 16, at 30 (quoting stakeholder view that Alice/Mayo is “hopelessly
subjective”); Taylor, supra note 20, at 227–30 (arguing that Alice/Mayo framework has “no objective guidance” and
“leaves the determination of eligibility to the unconstrained, subjective opinion of a patent examiner or judge”); Klein,
supra note 106, at 288 (criticizing patentable subject matter case law as amounting to “an ‘I know it when I see it’
approach”).
191 See, e.g., BCLT Report, supra note 16, at 561 (describing “uncertainty and confusion resulting from the Court’s
recent [patentable subject matter] jurisprudence”); accord USPTO PSM REPORT, supra note 16, at 30–31 (describing
views that the Alice/Mayo test yields “unpredictable” and “inconsistent” results).
192 See USPTO PSM REPORT, supra note 16, at 28; Klein, supra note 106, at 289–91 (criticizing the three judicially
created categorical exclusions as “extra-statutory” and proposing test that focuses on text of Section 101).

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American jurisprudence in cases such as Le Roy and Morse.193 Finally, many commentators and
stakeholders argue that the Alice/Mayo framework confuses patent law by conflating eligibility
under Section 101 with policy concerns—such as the obviousness of the invention and claim
breadth—that are better addressed by other provisions in the Patent Act, such as Sections 102,
103, and 112.194 For example, patent claims have been found to lack an inventive concept at
Alice/Mayo step two where they implement an abstract idea on conventional computer
hardware.195 Issues about what was “conventional” or “well-understood” at the time of the
invention, however, are questions usually reserved for novelty or nonobviousness analysis.196
Third, the Alice/Mayo framework is alleged to have detrimental effects on incentives to innovate,
especially in the biotechnology and computer software industries. Given the patent claims at issue
in Alice (a computer-implemented business method), Myriad (an isolated human DNA segment),
and Mayo (a drug dose optimization method), most observers agree that these two industries have
been the most affected by the Supreme Court’s Section 101 rulings.197 In the biotechnology
industry, stakeholders argue that the Alice/Mayo framework has limited their ability to obtain
patents on diagnostic methods and kits, personalized medicine, and isolated natural substances.198
Views in the computer industry are “sharply divided,” but at least some stakeholders argue that
Alice has devalued their patents and created uncertainty for their business.199 In both fields, some
stakeholders argue that the law of Section 101 is reducing incentives to innovate in these areas
and driving investment elsewhere.200
Finally, the uncertainty and unpredictability caused by Alice/Mayo is alleged to put the United
States at a disadvantage relative to international competitors. Some stakeholders argue that U.S.
competitiveness may be harmed because a lack of patent availability will drive investment in
certain industries to other countries where such inventions are more clearly patent-eligible.201
Lefstin, supra note 113, at 565 (arguing that Alice/Mayo test’s “inventive application” requirement rests on a “basic
misapprehension” of the 19th century English case cited by the Supreme Court); USPTO PSM REPORT, supra note 16,
at 27–28 (same).
194 See USPTO PSM REPORT, supra note 16, at 31–32; Taylor, supra note 20, at 157 (“[T]he current approach to
determining patent eligibility confuses the relevant policy concerns underlying numerous discrete patent law
doctrines.”); see also Risch, supra note 21, at 594 (arguing that the Court’s patentable subject matter doctrine would be
more consistent and rigorous if replaced with a strict application of other patentability doctrines such as obviousness,
novelty, utility, inventorship, written description, and enablement). This criticism has been echoed by Supreme Court
Justices. See Parker v. Flook, 437 U.S. 584, 600 (1978) (Stewart, J., dissenting) (“[The majority] strikes what seems to
me an equally damaging blow at basic principles of patent law by importing into its inquiry under 35 U.S.C. § 101 the
criteria of novelty and inventiveness.”).
195 See, e.g., Elec. Power Grp., 830 F.3d at 1355.
196 See, e.g., Berkheimer v. HP Inc., 881 F.3d 1360, 1368–69 (Fed. Cir. 2018) (noting that Alice/Mayo step two
determination of whether claims are “well-understood, routine and conventional” overlaps with Section 102 novelty
inquiry).
197 USPTO PSM REPORT, supra note 16, at 34–35 (“Among members of the public, there was a general consensus that
two industries have been most directly affected [by the Alice/Mayo framework]: life sciences and computer-related
technologies.”); see also BCLT Report, supra note 16, at 582–85 (examining the Alice/Mayo framework’s effects on
diagnostics, personalized medicine, biosciences, software, and information technology).
198 See USPTO PSM REPORT, supra note 16, at 34–35; BCLT Report, supra note 16, at 582–84.
199 See USPTO PSM REPORT, supra note 16, at 37–38 (characterizing the views on Alice/Mayo in the computer
industry as “sharply divided”); BCLT Report, supra note 16, at 582–84.
200 See USPTO PSM REPORT, supra note 16, at 35, 38; BCLT Report, supra note 16, at 583.
201 See, e.g., Stoll, supra note 23 (“The courts’ focus on subject matter eligibility as a mechanism to deny patents for
[inventions in diagnostics and personalized medicine] will drive investment into research in these technologies to other
areas. We will lose our edge in the world . . . .”); accord USPTO PSM REPORT, supra note 16, at 34; Kevin Madigan &
Adam Mossoff, Turning Gold into Lead: How Patent Eligibility Doctrine Is Undermining U.S. Leadership in
(continued...)
193

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Others argue that one effect of Alice/Mayo is a loss of any patent protection for certain inventions,
which will enable competitors to “free ride” off of American innovation.202

Defenses of the Alice/Mayo Framework
Defenders of the current law of Section 101 respond that these criticisms of Alice/Mayo are
overstated, or that the Supreme Court’s reinvigoration of Section 101 has important benefits for
the patent system. As to the subjective or unpredictable nature of Section 101 doctrine, there is
some empirical evidence that the Alice/Mayo framework is not as unpredictable as is sometimes
claimed.203 Some commentators also observe that uncertainty in patentable subject matter law is
hardly a new phenomenon,204 and may even be “inevitable.”205 A subjective or “amorphous”
approach to patentable subject matter, on this view, may have certain benefits, including
flexibility and adaptability to new technologies.206 Moreover, even if one views the current state
of the law as unacceptably vague, courts may eventually clarify or change Section 101 doctrine in
line with the long history of common law development in this area.207
As to the legal correctness of Alice/Mayo, defenders of the framework note that while the
judicially created categories are not directly grounded in the text of Section 101, they have been
treated as part of the law “as a matter of statutory stare decisis going back 150 years.”208 As to
Mayo’s reliance on 19th century English patent law, some commentators defend the Supreme
Court’s “inventive application” requirement as a faithful reading of this precedent.209 Finally,
although the Alice/Mayo framework may overlap with other patent law doctrines, several
commentators and judges of the Federal Circuit argue that Section 101 serves purposes distinct

Innovation, 24 GEO. MASON L. REV. 939, 942–44 (2017) (expressing “concern about the U.S. conceding its gold
standard patent system to China and Europe” because of the uncertainty of the Alice/Mayo framework).
202 See, e.g., Davis, supra note 23 (quoting former USPTO Director David Kappos as stating that international
competitors “no longer have to steal U.S. technology in [biotech and software], since they can now take it for free”).
203 See Jason D. Reinecke, Is the Supreme Court’s Patentable Subject Matter Test Overly Ambiguous? An Empirical
Test, 2019 UTAH L. REV. 581, 583 (2019) (empirical study indicating that while “the [Alice/Mayo] test is likely not a
beacon of absolute clarity, it is not completely amorphous,” as patent prosecutors correctly predicted judicial results
67.3% of the time based only on claim language).
204 See, e.g., Duffy, supra note 113, at 623–38 (reviewing 100-year history of failed rules and tests for patentable
subject matter and observing that “instability in the law of patentable subject matter” is a recurring issue) & id. at 616
(citing 19th century treatise writers noting difficulty and complexity of the patentable subject matter); Risch, supra note
21, at 591 (criticizing, in 2008, the “currently confused and inconsistent jurisprudence of patentable subject matter”);
Donald S. Chisum, The Patentability of Algorithms, 47 U. PITT. L. REV. 959, 992 (1986) (noting “confusion and
arbitrary distinctions” in the law of the patentability of computer software resulting from the Benson decision).
205 Morris, supra note 106, at 107 (arguing that the Court’s “intuitive” approach to patentable subject matter
determinations is “inevitable”).
206 Id. at 107–09 (arguing that intuitive approach to Section 101 may be “desirable” because “there is simply no other
more rigorous and yet durable way of identifying the proper boundaries for patentable subject matter” and “vagueness
provides the flexibility necessary to adjust future technological developments”); Duffy, supra note 113, at 639 (“[T]he
traditional doctrines of patentable subject matter—the prohibition against patenting abstract ideas, natural phenomena,
and principles of nature—have survived because . . . they have been amorphous.”).
207 See USPTO PSM REPORT, supra note 16, at 23–24 (expressing stakeholder views that the Court’s decisions are part
of the normal common law development of Section 101, and that the Federal Circuit’s subsequent development of the
law may be “headed in the right direction”).
208 Bilski v. Kappos, 561 U.S. 593, 602 (2010) (citing Le Roy v. Tatham, 55 U.S. (14 How.) 156, 174–75 (1853)).
209 See Brief of Nine Law Professors as Amicus Curiae in Support of Petitioners at 8–16; Mayo Collaborative Servs. v.
Prometheus Labs., Inc., 566 U.S. 66 (2012) (No. 10-1150), 2011 WL 4071921.

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from Sections 102, 103, and 112.210 For example, even if the invention in Myriad—an isolated
human DNA sequence discovered to be linked to increased breast cancer risk—was novel,
nonobvious, and sufficiently disclosed, some commentators would still argue that the invention
should not be patented based on harm to future innovation or moral concerns about patenting
human DNA.211
Regarding the alleged detrimental effects of the Court’s Section 101 decisions on innovation,
some stakeholders point to countervailing benefits either generally or in certain industries. In
particular, some stakeholders in industries (such as computer software) affected by litigation by
patent assertion entities212 argue that Section 101 is a useful and important tool for weeding out
overly broad or vague patents at the outset of litigation.213 Other commentators point to general
utilitarian or moral benefits of robust exclusions for patents on basic discoveries in science and
nature.214
Lastly, in response to concerns about the Alice/Mayo framework’s effect on international
competitiveness, some commentators assert that these changes are good for the United States as a
geopolitical matter.215 In particular, restricted patent-eligibility standards may benefit U.S.
consumers if a lack of patent protection leads to increased competition and lower prices for
certain products without harming innovation.216

Views on the Purposes of Section 101
There is a long-running debate over the functions and purposes that Section 101 serves in the
patent system. For its part, the modern Supreme Court has largely settled on the “preemption
rationale” for the judicially created subject matter exclusions. These decisions assert that abstract
ideas, laws of nature, and natural phenomena should not be patentable because permitting a
monopoly on the “‘basic tools of scientific and technological work’ . . . might tend to impede
innovation more than it would tend to promote it,”217 in that such patents would “significantly
impede future innovation.”218 The gist of the preemption rationale is that Section 101 functions to

210 See, e.g., Morris, supra note 106, at 113 (“To be sure, patentable subject matter overlaps with and serves some of

the same purposes as the other patentability requirements . . . . But only patentable subject matter serves to distinguish
patentable technology from unpatentable discoveries, information, and human thought and activity.”); Lemley et al.,
supra note 21, at 1330–32 (distinguishing purpose of Section 101 from Section 112); accord Mayo, 566 U.S. at 90–91;
Athena Diag., Inc. v. Mayo Collaborative Servs., 927 F.3d 1333, 1337–39 (Fed. Cir. 2019) (Dyk, J., concurring in the
denial of rehearing en banc).
211
See generally infra “Views on the Purposes of Section 101.”
212 A patent assertion entity, sometimes called a nonpracticing entity or (pejoratively) a “patent troll,” is a loose term
for an individual or organization that seeks to license or litigate patents, but does not itself practice the patented
invention. See Colleen V. Chien, From Arms Race to Marketplace: The Complex Patent Ecosystem and Its
Implications for the Patent System, 62 HASTINGS L.J. 297, 326–27 (2010) (discussing distinction among various types
of nonpracticing patent entities).
213 USPTO PSM REPORT, supra note 16, at 24–26; BCLT Report, supra note 16, at 596; Gugliuzza, supra note 25, at
652–53.
214 Sarnoff, supra note 113, at 106–24 (reviewing asserted utilitarian and moral benefits of robust Section 101
exclusions); see generally infra “Views on the Purposes of Section 101.”
215 USPTO PSM REPORT, supra note 16, at 27.
216 Id.
217 Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 71 (2012) (quoting Gottschalk v. Benson, 409
U.S. 63, 67 (1972)); Alice Corp. Pty. v. CLS Bank Int’l, 573 U.S. 208, 216 (2014) (“We have described the concern
that drives [the ineligible categories of patentable subject matter] as one of pre-emption.”).
218 Mayo, 566 U.S. at 91.

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prevent patents that reach so broadly that they “threaten downstream innovation” by preempting
all uses of a natural law, abstract idea, or fundamental research tools.219
The preemption rationale is not the only potential justification for Section 101, however.
Although a complete survey of the various rationales proffered for Section 101 is beyond the
scope of this report, at least four broad categories of rationales for Section 101 have been
proposed.220
First, some commentators argue that Section 101’s purpose is to identify certain patents or
categories of patents that should not be granted because their economic harms exceed their
benefits—that is, their net social costs are negative for innovation, or more generally.221
Preemption theory, which claims that certain overbroad patents should be denied patent
protection under Section 101 because of their negative effects on downstream innovation, is an
example from this group.222
Second—in what is in some sense a special case of the first rationale—other commentators assert
that Section 101’s purpose is to identify and deny patents to categories of inventions that would
have been developed even without a patent incentive.223 For example, several commentators have
argued the patents on business methods should be excluded under Section 101 either because they
affirmatively harm innovation and the economy, or because they are simply unnecessary because
sufficient incentives to create business methods would exist even if patents are unavailable.224
Third, some commentators assert that Section 101 (or elements of Section 101 doctrine) are based
not on economic considerations but on moral or ethical concerns.225 For example, the judicial
prohibition on patenting products of nature—such as human DNA sequences—may be motivated

219 See, e.g., Lemley et al., supra note 21, at 1346–47; accord Benson, 409 U.S. at 72 (rejecting patent because it would

“wholly pre-empt the mathematical formula and in practical effect would be a patent on the algorithm itself”). But see
Katherine J. Strandburg, Much Ado About Preemption, 50 HOUS. L. REV. 563, 566 (2012) (critiquing preemption
rationale’s “sole focus on broad downstream impact” as not providing a satisfactory explanation for the Supreme
Court’s Section 101 case law).
220 See generally J. Jonas Anderson, Applying Patent-Eligible Subject Matter Restrictions, 17 VAND. J. ENT. & TECH. L.
267, 269–40, 279–86 (2015) (surveying the “diverse set of proposed theories” of Section 101 and categorizing them
into several broad categories).
221 See Anderson, supra note 220, at 284–85 (overviewing this group of theories); see, e.g., David S. Olson, Taking the
Utilitarian Basis for Patent Law Seriously: The Case for Restricting Patentable Subject Matter, 82 TEMP. L. REV. 181,
184 (2009) (arguing that patentable subject matter doctrine should be driven by looking at when “granting a patent right
for this type of innovation causes more loss to society than gain”).
222 See supra note 219 and accompanying text.
223 See Anderson, supra note 220, at 285–86 (overviewing this group of theories); see, e.g., Pamela Samuelson, Benson
Revisited: The Case Against Patent Protection for Algorithms and Other Computer Program-Related Inventions, 39
EMORY L.J. 1025, 1136 (1990) (arguing that software should not be patentable in part because “the fact that this growth
[in the software industry] has occurred without the aid of patent protection is powerful evidence that patent protection
is not necessary for the software industry to thrive”).
224 See, e.g., Rochelle Cooper Dreyfuss, Are Business Method Patents Bad for Business?, 16 SANTA CLARA COMPUTER
& HIGH TECH. L.J. 263, 274 (2000) (arguing that business method patents are unwise because they “adversely affect
innovation, and worse, the economy”); accord Bilski v. Kappos, 561 U.S. 593, 651 (2010) (Stevens, J., concurring in
the judgment) (arguing that business methods should not be patentable because there are “ample incentives to develop
business methods even without patent protection” (quoting Dan L. Burk & Mark A. Lemley, Policy Levers in Patent
Law, 89 VA. L. REV. 1575, 1618 (2003))).
225 See Anderson, supra note 220, at 286 (overviewing this group of theories); see, e.g., Sarnoff, supra note 113, at 84–
90 (surveying religious and deontological bases for prohibition on patenting science, nature, and ideas); Tun-Jen
Chiang, Competing Visions of Patentable Subject Matter, 82 GEO. WASH. L. REV. 1858, 1860 (2014) (arguing that
Section 101 determinations are “often about noneconomic moral values”).

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by noneconomic, deontological notions of human dignity, or the inviolability of natural
creation.226
Finally, some commentators believe that Section 101 serves no independent purpose in patent law
not already better served by other patentability requirements.227 On this view, Section 101’s
judicially created exceptions to patentable subject matter should simply be eliminated as an
independent requirement for patentability, in favor of a rigorous application of the other
patentability requirements in Sections 102, 103, and 112 of the Patent Act.228

Potential Options for Section 101 Reform
Before examining the particular approaches used in USPTO guidance and proposed legislative
reforms, this section reviews some of the general ways in which Section 101 may or may not be
reformed. These different paths are introduced to contextualize the current Section 101 reform
proposals within the universe of possible reforms. This list is not exhaustive, nor are each of these
options necessarily mutually exclusive.
At a general level, most of the proposed paths forward for Section 101 fall into one of four
categories.229 First, some oppose any legislative intervention, proposing instead to allow the
courts to continue to develop and refine the standards for patent eligibility.230 Second, some
propose replacing the Alice/Mayo framework with an explicit list of subject matter that is patenteligible or -ineligible, similar to the approach that is used for European patents.231 Third, some
propose replacing the Alice/Mayo framework with a different, usually lower, standard for patent
eligibility, such as a requirement that the invention result from human effort, exist outside the
human mind, or contribute to the technological arts.232 Fourth, some propose to do away with any
limitations on patentable subject matter, beyond the four statutory categories and other existing
statutory patentability requirements.233

Continued Common Law Judicial Development
Congress could leave Section 101 as it is, and allow the courts and the USPTO to continue
developing the law of patent-eligible subject matter. Stakeholders and commentators may support
this option for several different reasons. Some may disagree that the Alice/Mayo framework is as

226 Chiang, supra note 225, at 1873–81.
227 See Anderson, supra note 220, at 280 (overviewing this group of theories).
228 See, e.g., Risch, supra note 21, at 591–94 (articulating this view); Davis, supra note 23 (quoting former USPTO

Director David Kappos as calling for abolishing Section 101 and instead “faithfully applying other areas of patent law
to ensure that patents are not obvious or anticipated or lacking in written description”).
229 See David O. Taylor, Amending Patent Eligibility, 50 U.C. DAVIS L. REV. 2149, 2189–2211 (2017) (listing proposed
Section 101 reforms, including a European-style “laundry list” of exclusions, a new “workable eligibility standard,” or
the elimination of the judicially created ineligible categories); USPTO PSM REPORT, supra note 16, at 39–46
(reviewing proposed Section 101 recommendations, including continued judicial and/or administrative development,
codification of explicitly defined Section 101 exceptions, or new standards for patent eligibility); BCLT Report, supra
note 16, at 562–66 (same).
230 See USPTO PSM REPORT, supra note 16, at 39–41; BCLT Report, supra note 16, at 566.
231 See Taylor, supra note 229, at 2198–2201; USPTO PSM REPORT, supra note 16, at 43–45; BCLT Report, supra note
16, at 564.
232 See Taylor, supra note 229, at 2202–06;

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/crs%3AR45918. Public record. Not legal advice.