The Tableau Method (3)
2023-2 Modal Logic (Segment 2) Q) Evaluate the following wffs in the B-semantics + inclusion requirement and determine in what systems, K, T, S4, β, S5 (if any) they are valid. 1. (∃y)LM(ϕy ⊃ (∀x)ϕx) 2. L(∃x)(Lϕx ∨ ψy) ⊃ (∃x)L(Lϕx ∨ ψy) 3. L(M(∃x)ϕx ⊃ (∃x)Mϕx) 4. L(∃x)ϕx ⊃ (∃x)Lϕx