of nature, or abstract idea (collectively, a principle). The clue to the patent-eligibility of processes that do not involve substance-transformation is whether the process implements its underlying principle nontrivially with a machine or other device specifically adapted to carry out the process. Although the Supreme Court has left open the possibility that a process might be patent-eligible that did not transform one substance into another and that was not implemented in a nontrivial manner with a device specifically designed to carry out the process, no such example has yet been recognized. These clues to patent-eligibility do not, however, fully exhaust the subject. There are at least two other clues to the patent-eligibility of products and processes. The categories of patenteligible things One of these clues need not detain us long. It is that the patent statute (35 U.S. Code 1 101) lists specific categories of patent-eligible things: machines, articles of manufacture, compositi...