Section 101 Patent Eligibility: Abstract Ideas, Laws of Nature, and Alice

Patent eligibility under 35 U.S.C. § 101 determines whether an invention belongs to a category of subject matter that can be patented at all — a threshold question that precedes the novelty, non-obviousness, and utility inquiries. The Alice Corp. v. CLS Bank International decision (573 U.S. 208, 2014) restructured how the USPTO and federal courts evaluate software, business methods, and biotech claims under this statute. This page provides a comprehensive reference treatment of the § 101 framework, the two-step Alice/Mayo test, classification boundaries across the three judicial exceptions, and the practical tensions that continue to generate litigation and examination disputes.

• Definition and scope
• Core mechanics or structure
• Causal relationships or drivers
• Classification boundaries
• Tradeoffs and tensions
• Common misconceptions
• Checklist or steps (non-advisory)
• Reference table or matrix
• References

Definition and scope

Section 101 of Title 35 of the U.S. Code defines patent-eligible subject matter as "any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof." This language is deliberately broad, but the Supreme Court has carved out three categories that fall outside its reach regardless of how a claim is drafted: abstract ideas, laws of nature, and natural phenomena. These are collectively called the "judicial exceptions," a doctrine rooted in the principle that such concepts are the basic tools of scientific and technological work and cannot be monopolized by any single inventor.

The statutory framework sits within the broader patent eligibility requirements that govern prosecution before the United States Patent and Trademark Office (USPTO). A rejection under § 101 is a threshold rejection — it does not reflect on whether the invention is novel or non-obvious, only on whether the claimed subject matter is the type that the patent system was designed to protect.

The judicial exceptions have been developed through a line of Supreme Court cases spanning more than a century, from O'Reilly v. Morse (1854) through Bilski v. Kappos (561 U.S. 593, 2010) and culminating in the three modern anchor decisions: Mayo Collaborative Services v. Prometheus Laboratories (566 U.S. 66, 2012), Association for Molecular Pathology v. Myriad Genetics (569 U.S. 576, 2013), and Alice Corp. v. CLS Bank International (573 U.S. 208, 2014).

Core mechanics or structure

The operative analytical framework is the two-step test established in Alice and drawn from Mayo. The USPTO codified this test in its 2019 Revised Guidance on Subject Matter Eligibility (84 Fed. Reg. 50, January 7, 2019), which reorganized Step 2A into two prongs.

Step 1 — Statutory Category Check: The claim must fall within one of the four statutory categories: process, machine, manufacture, or composition of matter. Claims that fall entirely outside these categories — such as transitory signals in some interpretations — are rejected without further analysis.

Step 2A, Prong 1 — Identify the Judicial Exception: The examiner or court asks whether the claim recites a judicial exception. The USPTO's 2019 Guidance groups abstract ideas into three subsets: (1) mathematical concepts, (2) certain methods of organizing human activity (including fundamental economic practices and commercial interactions), and (3) mental processes that can be performed in the human mind.

Step 2A, Prong 2 — Integration into a Practical Application: If a judicial exception is recited, the analysis asks whether the claim as a whole integrates that exception into a practical application. Indicators of integration include improvement to the functioning of a computer itself, improvement to another technology, application of the exception with a particular machine, transformation of an article, or a particular treatment or prophylaxis of a disease.

Step 2B — Inventive Concept: Only if the claim does not integrate the exception into a practical application does the analysis reach Step 2B, which asks whether the additional claim elements, individually or as an ordered combination, provide an "inventive concept" — something "significantly more" than the exception itself. Routine, conventional, or well-understood activity does not supply the required inventive concept, as confirmed in Alice at 573 U.S. 221.

Causal relationships or drivers

The expansion of § 101 rejections following Alice was measurable and immediate. The USPTO's own data showed that § 101 rejection rates in software-related art units rose sharply between 2014 and 2016, with the share of applications receiving at least one § 101 rejection in certain technology classes exceeding 90 percent in the period documented in the USPTO Patent Technology Monitoring Team reports.

Three doctrinal drivers created this environment. First, Mayo held that adding the words "apply it" or equivalent language to a law of nature does not constitute enough to cross the § 101 threshold. Second, Alice extended the Mayo framework explicitly to abstract ideas, closing what some practitioners had treated as a gap between the two doctrines. Third, the Federal Circuit's divided decisions in the years following Alice — including Enfish, LLC v. Microsoft Corp. (822 F.3d 1327, Fed. Cir. 2016) and McRO, Inc. v. Bandai Namco Games America Inc. (837 F.3d 1299, Fed. Cir. 2016), which found patent-eligible claims, alongside decisions finding ineligibility — produced inconsistent signals that made examination unpredictable.

The broader regulatory context for these developments is addressed in the regulatory context for patent law, which covers the USPTO's rulemaking authority and the interplay between examination guidance and binding judicial precedent.

Classification boundaries

The three judicial exceptions have distinct analytic boundaries, though the boundaries frequently overlap in practice.

Abstract Ideas are the most litigated category. The Supreme Court declined in Alice to define the full contours of the abstract idea exception, instead relying on the "directed to" language and comparison to prior cases. The USPTO's 2019 Guidance narrows examination to three enumerated subgroups: mathematical concepts (including mathematical relationships, formulas, and calculations), certain methods of organizing human activity (including fundamental economic principles, commercial or legal interactions, managing personal behavior), and mental processes. Claims entirely executable in a human mind without external machinery fall within the mental process subgroup.

Laws of Nature encompass natural correlations, relationships, and phenomena, regardless of whether the applicant discovered them. Mayo held that a claim covering a natural relationship between thiopurine drug metabolite levels and therapeutic efficacy was directed to a law of nature, even though the relationship was previously unknown. The critical boundary is whether the claim adds meaningful limitations beyond simply observing or detecting the natural relationship.

Natural Phenomena and Products of Nature were addressed most directly in Myriad Genetics, where the Supreme Court held that isolated genomic DNA sequences are not patent eligible because they are products of nature, while complementary DNA (cDNA) that does not occur naturally was found eligible. The distinction rests on whether human intervention creates something with markedly different characteristics from what exists in nature.

The patentable subject matter analysis for each of these categories is also addressed in conjunction with software patent law and biotechnology patent law, which face distinct examination challenges under § 101.

Tradeoffs and tensions

Section 101 generates four persistent doctrinal tensions that appear in both academic commentary and Federal Circuit litigation.

Claim Drafting vs. Substantive Limitation: Broad claiming strategies, particularly those reciting functional results rather than specific technical implementations, tend to draw § 101 rejections. Narrowing claims to recite specific structural or operational limitations often helps overcome rejection but may reduce the practical scope of protection — a direct tradeoff between eligibility and breadth.

Preemption vs. Practical Application: The theoretical justification for the judicial exceptions is preemption concern — that a patent on an abstract idea would foreclose all uses of that idea. Yet courts and the USPTO have largely moved away from explicit preemption analysis to the more formalized Alice/Mayo steps, creating a tension between the doctrine's stated purpose and its operational application. A claim can fail Step 2B even if it does not actually preempt the underlying concept in any broad sense.

Biotech Upstream Claims: Following Myriad and Mayo, claims to diagnostic methods and genetic materials face heightened § 101 scrutiny. Innovators argue this creates a gap in protection for investment-intensive upstream discoveries, while critics of broad eligibility argue the exceptions protect the research commons. This tension is particularly acute in the biotechnology patent law and pharmaceutical patent law contexts.

Clarity and Predictability: The absence of a bright-line test for abstract ideas — explicitly acknowledged by the Supreme Court in Alice — means that outcome prediction is unreliable. The Federal Circuit has acknowledged internal disagreement. In Berkheimer v. HP Inc. (881 F.3d 1360, Fed. Cir. 2018), the court held that whether additional claim elements represent well-understood, routine, and conventional activity is a question of fact, adding a factual dimension to what had been treated as a purely legal analysis. A complete overview of the patent system framework is available through the site index.

Common misconceptions

Misconception 1: A § 101 rejection means the invention is not patentable.
A § 101 rejection is a rejection of the claim as written, not a final determination that no patent can issue. Claims can be amended to recite patent-eligible subject matter — for example, by adding specific technical implementation details that integrate an abstract idea into a practical application.

Misconception 2: If a claim involves a computer, it is patent eligible.
Alice directly rejected this position. The Supreme Court held at 573 U.S. 223 that adding "apply it with a computer" or limiting a method to computer implementation does not automatically supply an inventive concept when the computer is invoked in a purely conventional way.

Misconception 3: Novelty saves a claim from a § 101 rejection.
Section 101 eligibility and § 102 novelty are independent inquiries. A claim can be entirely novel and non-obvious yet still be directed to a judicial exception. The Mayo claims covered a correlation that had not been previously patented — novelty was not disputed — yet the Supreme Court unanimously found the claims patent ineligible.

Misconception 4: The 2019 USPTO Guidance has the same legal weight as a Federal Circuit decision.
USPTO examination guidance is binding on examiners but is not binding on federal courts. The Federal Circuit applies its own § 101 case law, and a claim that survives examination under the 2019 Guidance can still be invalidated in post-grant proceedings or litigation.

Misconception 5: Natural product claims are always ineligible after Myriad.
The Myriad holding applies to products that are not markedly different from their natural counterparts. Claims to structurally distinct molecules, formulations with new utility, or engineered biological constructs that differ meaningfully from natural products may still satisfy § 101 under the markedly different characteristics analysis.

Checklist or steps (non-advisory)

The following sequence reflects the analytical steps applied during USPTO examination and Federal Circuit review under the Alice/Mayo framework, as codified in the 2019 Revised Subject Matter Eligibility Guidance:

1. Determine the statutory category — Confirm the claim recites a process, machine, manufacture, or composition of matter under 35 U.S.C. § 101.
2. Identify the judicial exception — Determine whether the claim recites an abstract idea (mathematical concept, method of organizing human activity, or mental process), a law of nature, or a natural phenomenon.
3. Apply Prong 1 of Step 2A — If no judicial exception is recited, the claim is eligible; stop analysis.
4. Apply Prong 2 of Step 2A — Evaluate whether the claim as a whole integrates the exception into a practical application by examining all additional claim elements for practical application indicators.
5. Check for preemption concerns — Consider whether the claim scope forecloses all practical applications of the exception (though this is not a standalone test).
6. Apply Step 2B if needed — If practical application is not established, identify whether additional elements individually or in ordered combination provide significantly more than the exception itself.
7. Evaluate conventionality as a factual question — Per Berkheimer, the characterization of additional elements as well-understood, routine, and conventional must be supported by evidence, not bare assertion.
8. Consider dependent claims separately — Dependent claims with additional technical limitations may be independently eligible even if the independent claim is rejected.

Reference table or matrix