"older formulation of Pauli exclusion principle" Is there any old formulation of pauli's principle? If so, is it explain that "forbiding the presence of two electrons in the same quantum state"? I need that explanation.
Re: "older formulation of Pauli exclusion principle" Two electrons can't occupy the same quantum state, what kind of explanation are you looking for? What in the present formulation makes you not understand it?
Re: "older formulation of Pauli exclusion principle" Old formulation? Mmm... don't know exactly what that means... but consider this: The many-body wavefunction must be antisymmetric under interchange of the variables describing any two electrons. This is more general than a description in terms of "orbitals", but of course if an orbital description is possible it forbids two electrons to be in the same orbital.