 In order to fully understand Leibniz’s conception of a sufficient reason, we need to also understand his theory of truth and its relationship to his theory of modality. Let us begin with truth. To keep things simple, we will focus only on categorical propositions of subject-predicate form. A proposition is true, according to Leibniz, just in case the concept of the predicate is contained in the concept of the subject. Uncontroversially, the concept of the predicate is unmarried is contained in the concept bachelor and it is this conceptual containment which explains the truth of the statement bachelors are unmarried. But Leibniz makes the further highly controversial claim that all true statements are true for this reason, even statements like Caesar crossed the Rubicon. That is, this statement is true because the concept crossed the Rubicon is contained in the concept of Caesar. This theory of truth is sometimes called the conceptual containment theory of truth. It has as a consequence that all truths are analytic. But wouldn’t such a theory entail that all truths are necessary? After all, how could an analytic truth be contingent?