Ah, the
principle. IANA physicist, but I've never been happy with this here thingy. As the article states, "Wolfgang Pauli gave physics his exclusion principle as a way to explain the arrangement of electrons in an atom. His hypothesis was that only one electron can occupy a give quantum state." This is a principle without an explanation. It's one of those physics things that you have to take on faith, and because nothing works without it. AFAIK there's never been any real explanation of _why_ this principle exists, or what causes it to be true. I suppose this could be considered a kind of physics 'axiom', but that's still not very satisfactory.
Have any theorists tried to construct a plausible universe model where the exclusion principle is not true or not applicable (and everything doesn't just collapse in on itself, of course)?
Oh, BTW - this is just one of many examples where science does, in fact, depend on pure faith. This is a lesson to overly dogmatic anti-religionists - or, as WC Fields once said, "Everyone believes in something. I believe I'll have another drink." :D