@article{Pietruszczak_2010, title={Simplified Kripke style semantics for some very weak modal logics}, volume={18}, url={https://apcz.umk.pl/LLP/article/view/LLP.2009.013}, DOI={10.12775/LLP.2009.013}, abstractNote={In the present paper we examine very weak modal logics C1, D1, E1, S0.5◦, S0.5◦+(D), S0.5 and some of their versions which are closed under replacement of tautological equivalents (rte-versions). We give semantics for these logics, formulated by means of Kripke style models of the form &lt;w,A,V&gt;, where w is a «distinguished» world, A is a set of worlds which are alternatives to w, and V is a valuation which for formulae and worlds assigns the truth-vales such that: (i) for all formulae and all worlds, V preserves classical conditions for truth-value operators; (ii) for the world w and any formula ϕ, V(⬜ϕ,w) = 1 iff ∀x∈A V(ϕ,x) = 1; (iii) for other worlds formula ⬜ϕ has an arbitrary value. Moreover, for rte-versions of considered logics we must add the following condition: (iv) V(⬜χ,w) = V(⬜χ[ϕ/ψ],w), if ϕ and ψ are tautological equivalent. Finally, for C1, D1and E1 we must add queer models of the form &lt;w,V&gt; in which: (i) holds and (ii’) V(⬜ϕ,w) = 0, for any formula ϕ. We prove that considered logics are determined by some classes of above models.}, number={3-4}, journal={Logic and Logical Philosophy}, author={Pietruszczak, Andrzej}, year={2010}, month={Mar.}, pages={271–296} }