He doesn't have to prove it. Using the scientific method, something is always true until proven false. That's because it's very difficult (often impossible) to prove something true, while very easy to prove false.
You could say that cats can't type, but my cat sticks extra characters in my code all of the time.
You could say that cats don't have the brain capacity for linquistic communication, but that can't be proven either.
@duoas: padfoots a dog/escaped criminal on the run who is killed by their cousin kind of name. what happened to cody one? and how weird... i used to have a cat named patches that looked like that