In 1936, Alonzo Church proved that that stuff is mathematics. Church created lambda calculus, a formal means of writing mathematical expressions and also a tool that can be used to program a state machine. That is, any program written in a language such as C is a trivial translation of a set of purely mathematical lambda-calculus expressions.

So where is the line drawn between software and mathematical expression? Based on Church’s and Turing’s work, there is none. Any legal attempt to force a wedge between pure math and software will fail because the two are one and the same. A patent on a program is a patent on a mathematical expression, regardless of whether it is expressed in C, Lisp, or lambda calculus.

BUT WHILE DEMOLISHING the distinction between software and math, Turing and Church’s work offers a natural division between patentable machinery and unpatentable mathematics-exactly what we have been looking for. Let the devices that implement state machines-physical objects such as computers-be patentable, and the states to which they are set-information such as programs and data-remain unpatentable. The distinction meets the goal of ensuring that pure mathematics is not patentable while letting those who design faster and better computing devices patent their inventions.