2023-2 Modal Logic (Segment 3) Q) Explain the system S1. In what sense is it the case that the “unrestricted” rules of Necessitation does not hold in S1. Does pc tautology necessitation hold in S1 ? What is the Cresswell argument (See my SS1 paper) that S1 has no theorems of the form LL(p⊃ p)? Explain the semantic system for S2 and S3 and S4 where one introduces odd vs normal worlds. Note that b..