"The problem is that all software ultimately reduces to mathematical operations, yet only some software controls actual stuff, like the baking of rubber. If the rest is merely math and therefore unpatentable, does that mean we must deny patents to all software that runs nothing but itself? Back in the 1990s, courts were uncomfortable going that far. Computers were infiltrating more and more traditional bastions of patent protection—consumer products, telecommunications, medical devices, automobiles—and computer software itself had become a distinct technology industry. It seemed wrong to read Diamond v. Diehr so broadly as to deny patent protection to new enterprises, thus leaving the rising tide of software technology outside the system—along with the dreaded business method. So the lower courts found themselves caught between the Supreme Court’s antipathy toward excessively mathematical inventions and the proliferating reality of computer software. Searching for a single principle that would exclude equations from patentability without crippling innovation, the courts experimented unsuccessfully with one patentability test after another."