The best of all possible worlds

Recall the Principle of Sufficient Reason: nothing is so without a reason why it is so and not otherwise. Leibniz turns it on creation itself. God’s understanding contains infinitely many possible worlds — every complete, self-consistent way a universe could be. Only one was made actual. So there must be a sufficient reason why this one and not another.

Now add God’s nature. God is supremely powerful (can create any possible world), supremely wise (knows which is best), and supremely good (wills the best). A being with those attributes, choosing among all possible worlds for a reason, can have only one reason to prefer one world: that it is the best. Therefore, “God, in producing the universe, chose the best of all possible worlds” (Monadology §53–55; Theodicy). This is not optimism as a mood; it is a deduction from sufficient reason plus divine perfection.

What makes one world best? For Leibniz, the greatest perfection: the world yielding “the greatest variety of phenomena governed by the smallest number of laws” — maximal richness of effects from maximal simplicity of principles (Discourse §5–6). The best world is the most fecund and the most elegant: not the emptiest or the tidiest, but the one where the simplest laws generate the most reality.

But the obvious objection is evil. How can a world with genocide, disease, and agony be the best? Leibniz’s reply is his theodicy — a word he coined (from theos, God, + dikē, justice), the title of his 1710 book, meaning the justification of God in the face of evil. He distinguishes three kinds.

Metaphysical evil is finitude — the sheer limitation and imperfection built into being a creature rather than God. Any created thing is less than infinite; imperfection is unavoidable the moment God makes something that is not himself. Physical evil is suffering (pain, disease, disaster). Moral evil is sin — the wrong choices of free creatures (Theodicy, §21).

Two further moves sharpen the theodicy. First, God does not create evil; he permits it. Evil is a privation (privatio) — a lack of due goodness or being, not a positive stuff God manufactures, much as cold is absence of heat and darkness absence of light. Second, evils are permitted only as necessary components of the best whole: God would not allow a given evil unless a world containing it were, all things considered, better than any world without it. The unit of divine goodness is the whole world, not each isolated part.

Finally, Leibniz’s rationalism collides with the empiricists head-on. John Locke had argued the mind is a blank slate (tabula rasa): no innate ideas or principles; everything comes from experience (the old scholastic maxim ran: “nothing is in the intellect that was not first in the senses”). In his New Essays on Human Understanding (written c. 1704, a chapter-by-chapter reply to Locke’s Essay), Leibniz defends innate ideas and truths.

Hence Leibniz’s celebrated amendment to the empiricist slogan: “nothing is in the intellect that was not in the senses — except the intellect itself” (New Essays II.i). Grant the empiricists that particular sensory ideas come through experience; but the mind’s own structure — its capacity for necessary truth, its innate principles like non-contradiction and identity — is presupposed by experience, not derived from it. The senses give instances; only reason gives necessity and universality, which no finite run of experience could establish.