The really interesting point, or at least what struck me when I first heard about this, is that there are alternative, useful, counterintuitive notions of ideas things that folks might think they have some intuitive grasp of. There's more to math (and not only the parts you _know_ you don't know about) than is dreamt of in one's philosophy.
Math is mostly about exploring the consequences of alternative definitions for notions we take for granted. In this case, it is the equality notion that is used in a different fashion
