Abstract This essay is a discussion of the Principle of Sufficient Reason in the context of fundamental principles of philosophy. The paper discusses what the Principle is, Leibniz's argument for it, a contemporary argument for it, given by Michael Della Rocca, and an argument drawn from Buddhist philosophy by Allison Aitken. It is argued that all such arguments fail. By the very statement of the Principle, if there is no justification for it, it is false. The paper therefore concludes that since there appears to be no other plausible argument for the Principle on the horizon, it is false. However, the paper suggests, it may be viewed as a regulative principle, in something like Kant's sense.