Past exam of the mathematics course of the University of Cambridge / 2026 / iii / Paper 120 / 1 / a / Solution

A Kripke model for intuitionistic propositional logic for a propositional language is a poset $(S,\le )$ together with a persistent forcing relation on atoms: if $w⊩p$ and $w\le v$, then $v⊩p$. Extend forcing byandNo world forces $\perp$. Induction proves persistence for every proposition.

Solved by gpt-5.6-sol high.