Leibniz's Two Realms Revisited

In his attempt to reconcile piety and the new science, teleology and mechanism, final causation and efficient causation, Leibniz often speaks of there being two realms – a “kingdom of power or efficient causes” and “a kingdom of wisdom or final causes.” In this essay, I explore Leibniz’s attempt to apply this doctrine to the natural world. The essay falls into four main parts. The first part looks to Leibniz’s much neglected work in optics for the roots of his view that the world can be seen as being governed by two complete sets of equipotent laws. The second offers an account of how this picture of lawful over-determination is to be reconciled with Leibniz’s mature metaphysics. The third addresses a line of objection proposed by David Hirschmann to the effect that Leibniz’s two realms doctrine as applied to the physical world undermines his stated commitment to an efficient, broadly mechanical, account of the natural world. Finally the fourth part suggests that Leibniz’s thinking about the harmony of final and efficient causes in connection with corporeal nature may help to shed light on his understanding of the teleological unfolding of monads as well.