41 Pages Posted: 30 Nov 2005 Last revised: 14 May 2020

See all articles by Dan L. Burk

Dan L. Burk

University of California, Irvine School of Law

Mark A. Lemley

Stanford Law School


Inherency is a puzzle that runs throughout patent law. Patents are based upon descriptions of technology. However, technologies may have qualities that are unappreciated or unidentified in a patent description, but which are nonetheless present. The law refers to these unknown attributes as inherent in the product or process. What should be done about such characteristics or qualities of a technology that exist but are not explicitly described, either through ignorance or inadvertence? This problem is explicitly presented in at least five different patent doctrines: anticipation, the on-sale bar, priority disputes, double-patenting, and enablement; and it casts its shadow across the law governing subject matter, infringement, and obviousness.

Inherency is also perhaps the most elusive doctrine in all of patent law. The cases appear to flatly contradict each other, are often accompanied by dissents, and in the last three years alone have triggered one abortive en banc rehearing and strong calls for a second. In particular, the courts have split sharply over whether an element can be inherent in a prior art reference even if people of ordinary skill in the art do not appreciate the existence of that element.

In this Article, we argue that this confusion is largely unnecessary. While many courts have recited as gospel the idea that inherency requires knowledge or appreciation of the inherent element, in no case does the application of the inherency doctrine actually turn on knowledge of the element. Rather, the inherency cases are all ultimately about whether the public already gets the benefit of the claimed element or invention. If the public already benefits from the invention, even if they don't know why, the invention is inherent in the prior art. If the public doesn't benefit from the invention, there is no inherency.

In Part I, we examine the main thread of inherency cases, those arising out of the novelty and statutory bar provisions of the Patent Act. We explain how the courts got off track in their focus on knowledge, and why a focus on benefit clearly and consistently explains the doctrine. In Part II, we consider inherency in a different context, one in which the inventor must show possession of the claimed invention, either to prevent a new matter rejection or to establish priority of invention. Finally, in Part III, we discuss the broader implications of this rule, including what the inherency doctrine may mean for patents on DNA sequences and patents on drugs derived from traditional knowledge. A proper understanding of the inherency doctrine may offer a logical explanation for the product of nature cases, undermining the last significant exception to patentable subject matter.

Suggested Citation

Burk, Dan L. and Lemley, Mark A., Inherency. 47 William & Mary Law Review 371 (2005), Available at SSRN:

Dan L. Burk

University of California, Irvine School of Law ( email )

4500 Berkeley Place
Irvine, CA 92697-1000
United States
949-824-9325 (Phone)

Mark A. Lemley (Contact Author)

Stanford Law School ( email )

559 Nathan Abbott Way
Stanford, CA 94305-8610
United States

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