The high profile cases Bilski v. Kappos and Association for Molecular Pathology v. United States Patent and Trademark Office have renewed public debate about the proper scope of patentable subject matter. The subject matter inquiry has traditionally been treated as a threshold inquiry in patent law, serving a gate-keeping function by defining the types of inventions that are eligible for patent protection. The Patent Office and courts have approached the subject matter inquiry both by determining whether an invention falls into a statutory category-processes, machines, manufactures, or compositions of matter-as well as by determining whether an invention falls into a category excluded from subject matter eligibility-often described in recen...