I have just started thermodynamics (not with statistical approach but with macroscopic approach), in which the state postulate reads
Only two independent intensive properties of a simple compressible system are required to get all other properties necessary to describe the state .
So I was wondering that how this postulate may be justified . Since it is a postulate i think that it should feel like obvious (like a straight line is shortest path from one point to the other). But it is not so, therefore I am asking for a justification-
that how we know that this statement is indeed true Or if we can mathematically justify this through simpler (obvious) statements
A argument using macroscopic approach(not concerned with microscopic nature) is really what I am asking
However ,if it is too difficult to give such a justification then you can give a microscopic one. But former one would really help me.