Axiom 67: Pairing
For all sets x and y there exists a set T such that for all sets z we have z \in T if and only if we have at least one of the equalities z = x or z = y .
A theoretical quest.
Axiom 67: Pairing
For all sets x and y there exists a set T such that for all sets z we have z \in T if and only if we have at least one of the equalities z = x or z = y .