The most fundamental requirement of patent law is that a patented invention must be new. Given the longstanding, foundational nature of this novelty requirement, one might expect its contours to be well settled. Yet some of its most basic aspects remain unresolved. At the center of these unresolved issues lies what we term “real-world prior art.”

In patent law, prior art is something that predates an invention and may render it not new. “Real-world” prior art activities involve using or selling embodiments of the invention. Consider a few examples. Suppose Aleida demonstrates her invention to members of the public but does not allow them to touch it. Has she put the invention into “public use,” thus preventing others from obtaining a patent? Suppose Aleida keeps her invention secret but uses it to provide a commercial service. Has she put the invention into public use or placed it “on sale”? Or suppose Aleida offers her invention for sale to Charlise, who declines to purchase it. It is black-letter patent law that after one year passes, Aleida cannot patent this invention. But imagine that Bruno independently develops the same invention. Can he obtain a patent? These questions are not outlandish law school hypotheticals—they are central issues surrounding whether an invention is or is not novel. Yet litigation over these issues has resulted in conflicting outcomes and contradictory explanations, leaving lower courts and the Patent Office to flounder.

In this Article, we sort through this conceptual confusion and propose both doctrinal and institutional changes to elucidate this area of law. We argue that the value of resolving these questions runs much deeper than determining the answer to particular cases. The answers to these questions depend upon—and reveal—the conceptual superstructure of patent law. They implicate patent law’s most central questions: What does it mean for an invention to be new and thus patentable? What policy interests does patent law attempt to achieve, and whose interests does it aim to protect? And what are the conditions under which a party has forfeited the opportunity to obtain a patent? By addressing these issues, we endeavor to place the entire jurisprudence of patent novelty on more solid footing.