"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."