>>13
>>4 isn't proving anything.
If you use the Peano axioms (starting at 0 for convenience, otherwise you would need a bijection etc blahblahblah), you can just use the axiom that if a is a natural number, then S(a) is not 0. Since S(0) = 1, you can conclude that 0 is not equal to 1.
If you use the set theoretic construction you can say 0 is not 1 since {{}} is a proper subset of {{}, {{}}}, so the two can't be equivalent.
Or you can give your own construction of any number system you wish, but that's no guarantee it'll behave how you want.