In other words, the principle holds that there must always be a reason that suffices to explain anything that is. There only appeared to be truths of fact, or empirical truths, because of the human intellect's limitations on trying to grasp truths of reason. But for Leibniz, and thus the Wollfians too, everything is a windowless monad. There is no real interaction between these and what appears to be causal interaction is merely each monad reflecting the whole world through it own internal principles of development. God created a world with monads whose internal principles of development were consistant with each other, and also such that they constitute the best of all possible worlds.
Monads have differing abilities to reflect the world with clear and distinct representations.
Humans, of course are the best of any finite monads. Kant believes in genuine interaction. And because of this, he rejects the Wollfians reduction of the principle of sufficient reason to the principle of contradiction. Its original title is customarily abbreviated Nova Dilucidatio, since it was written in latin. It is available in Kant's Latin Writings edited by Lewis White Beck.