一句话:证明了 CS4 具有有限模型性质,并引入 GS4 与 S4I,证明三者均具有有限模型性质。
CS4 和 IS4 是模态逻辑 S4 的直觉主义变体,它们是否具有有限模型性质曾是一个长期未决问题。本文围绕 IS4 引入两个密切相关的逻辑:GS4 是在 IS4 上添加 Gödel-Dummett 公理得到;S4I 则是将模态关系与直觉主义关系的角色互换。作者随后证明 CS4、GS4 和 S4I 均具有有限模型性质。这一结果解决了 CS4 的有限模型性质问题,并为相关构造性模态逻辑的模型论性质提供了新认识。
The logics CS4 and IS4 are intuitionistic variants of the modal logic S4. Whether the finite model property holds for each of these logics has been a long-standing open problem. In this paper we introduce two logics closely related to IS4: GS4, obtained by adding the Gödel-Dummett axiom to IS4, and S4I, obtained by reversing the roles of the modal and intuitionistic relations. We then prove that CS4, GS4, and S4I all enjoy the finite model property.