[Sir Francis Dashwood]

It's not a scientific theory, it's a mathematical theorem. It can only be proved because the premises are axiomatic.

It was not axiomatic before Pythagoras...

[CarolinaGuitarman]

"It was not axiomatic before Pythagoras..."

And we can be thankful that Pythagoras (or one of his students, it isn't possible to know who actually came up with it) figured out the theorem. That doesn't make it science. Mathematics is a subset of logic, not science. It is an integral tool of science, but science is a different thing. It's possible to prove a mathematical theorem only because you can set the premises as true. When a formula is used to describe the real world, the math may be correct, but the relationship of that formula to reality will always be approximate. Newton's theory of gravity is an excellent example. It works for most objects in our normal experience but breaks down when you are dealing with very massive objects or very tiny objects. It has not been proved, nor can it be. It's still useful.