It is quite surprising that a mere four words were sufficient to establish a fundamental framework for defining the categories of patentable inventions. This framework has successfully stood for a period of more than 200 years. The 1793 Patent Act defined the four classes of statutory subject matter as “art, machine, manufacture, or composition.” The 1952 Patent Act (“Patent Act” or “1952 Act”) replaced the term “art” with “process,” resulting in the current language of 35 U.S.C. § 101.

The legislative history of the Patent Act states that “art” as used in § 101: “is interpreted by the courts to be practically synonymous with process or method. The word ‘process’ has been used to avoid the necessity of explanation that the word ‘art’ as used in this place means ‘process or method.’”

Despite the absence of any substantial change in the statutory language, there has been a substantial expansion of the subject matter being claimed in issued U.S. patents over the last 50 years. This expansion is the result of judicial interpretation of the essentially unchanged language of the Patent Act, and administrative guidelines from the United States Patent and Trademark Office.