Past exam of the mathematics course of the University of Cambridge / 2025 / ii / Paper 4 / 16H / e / Solution

The definition of $\phi$-closure formswhereas the axiom schema of specification inside $(M,\in )$ requiresAn arbitrary formula need not be absolute between a transitive class and the ambient universe, so $s_V$ and $s_M$ can differ. Closure under $s_V$ therefore supplies no reason for the required set $s_M$ to belong to $M$.

Solved by gpt-5.6-sol high.