Originally uploaded at SSRN.


In Nautilus (2014), the Supreme Court held “that a patent is invalid for indefiniteness if its claims...fail to inform, with reasonable certainty, those skilled in the art about the scope of the invention.” We don’t require perfect clarity because, as Festo (2002) highlights, patentees can’t achieve it. We don’t launch a post hoc judicial salvage operation to rescue slipshod text because, as the functional-claiming cases from the 1930s and 1940s highlight, others can’t adequately plan around it. Reasonably certain notice, then, is just right: § 112 “require[s] that a patent’s claims, viewed in light of the specification and prosecution history, inform those skilled in the art about the scope of the invention with reasonable certainty.” Nautilus. How then, should the Patent Office or the courts determine whether a given bit of disputed claim language is reasonably certain, for the protection of patentee and public alike? Reasonableness — a prudent point of balance between extremes — depends on context. And in Teva (2015), the Court confirmed that claim construction disputes, including claim definiteness, can turn on factual findings about a term’s meaning to artisans at a particular moment in time. This paper explores the contours of reasonably certain notice, using insights from negligence law’s reasonable care standard and procedural due process law’s reasonable notice standard. The upshot: To fairly judge the reasonableness of the notice that patent claim language provides, we must embed the claim language in more robust objective data about language usage than we currently consider — data about typical usage in the relevant art at the time the inventor applied for patent rights. Happily, we can adapt existing tools from corpus linguistics to analyze usage patterns, if we construct text corpora that are fit for purpose. The statutory demand for reasonable certainty, both at the Patent Office and in the courts, should prompt us to put these linguistics tools to work in patent law.