> To a computer scientist, this makes no sense, because every algorithm is as mathematical as anything could be.
But there is no reason for definitions in the law to mirror precisely the definitions of computer science. After all, a patentable drug formula is, to a chemist, just a description of a chemical system under the laws of chemistry. A patentable mechanical invention is, to a physicist, just a description of a physical system under the laws of physics.
The law very often makes distinctions between things that cannot be distinguished by their fundamental nature, on the basis of external policy reasons. The difference between murder and self-defense cannot be described by fundamental differences in the physical mechanics of the two actions. Now, that is not to say that software should be patentable, but rather that "all algorithms are math" is an irrelevant reason for making software not patentable. It's an interesting philosophical and theoretical point (not to mention, obviously true), but has no relation to the purposes of patent law.