Leibniz on Compossibility: Towards a Neo‐Logical Interpretation

Leibniz's concept of compossibility explains why not all possible substances are actualised, thereby resisting Spinoza's necessitarianism. Yet, the precise basis of incompossibility remains unresolved. The influential ‘logical’ interpretation—exemplified by the Hintikka–D'Agostino thesis—locates incompossibility in contradictions among relational predicates within complete concepts. While powerful, this account faces well‐known difficulties. In this paper, I contest the thesis while retaining a logical conception of compossibility. I first assess Jeffrey McDonough's overlooked non‐standard suggestion, which, though not fully successful, yields instructive insights. I then articulate what I call the Wilson–Sleigh interpretation, drawing on Margaret Wilson and Robert Sleigh, which identifies logically grounded routes to incompossibility not captured by the standard focus on relational predicates. I argue that this interpretation provides a better solution than the standard logical view.