Ümit Ege Atakan

The philosophy of logic literature has long been concerned with the demarcation problem of logicality. Since Alfred Tarski, a lot has been said about the question of what a logical notion is. However, surprisingly, the curiosity on this matter has never gone beyond the classical first-order logic (FOL). This paper will be an attempt to extend the discussion beyond classical FOL. Accordingly, in this paper, by adopting a Plurality-of-Logical-Domains approach, I will propose a new pluralism of logical notions. At its base, my pluralism will have Sher‘s (2022) account of invariance. Unlike Sher, following Bonnay (2008), I will not assume invariance under all isomorphisms but under potential isomorphisms as a criterion of a logical constant. This I will call the Weakened-Sher-Thesis. My proposed pluralism will become explicit as I go on to offer an application of it in Modal Logic.