Abstract

I discuss an argument for Leibniz’s principle of sufficient reason, the argument that he gives from considerations about necessary and sufficient conditions. I consider two versions that Leibniz offers, a longer and a shorter one. I also wish to assess a criticism of the longer version of Leibniz’s argument made by the distinguished Leibniz scholar Robert Merrihew Adams in 1994. Adams claims that Leibniz’s argument for the principle of sufficient reason begs the question. A simple formalization of the argument in propositional logic shows that this is not the case, but reveals two further difficulties. The first difficulty (a) has to do with the apparent failure of the derivation of the principle that the existence of the “aggregate” of the necessary conditions for the existence of a thing implies the existence of the sufficient conditions. The second difficulty (b) is that Leibniz’s second premise plays no obvious role in his derivation. I try to solve these problems, on his behalf.