Leibniz's Two Realms Revisited

Leibniz speaks, in a variety of contexts, of there being two realms – a “kingdom of power or efficient causes” and “a kingdom of wisdom or final causes.” This essay explores an often overlooked application of Leibniz’s famous “two realms doctrine” to the natural world. The first part turns to Leibniz’s work in optics for the roots of his view that nature can be seen as being governed by two complete sets of equipotent laws, with one set corresponding to the efficient causal order of the world, and the other to its teleological order. The second part 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 doctrine 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.