 Let us now consider one notable difference between the Monadologie and the Principes de la Nature et de la Grace. In the Principes de la Nature et de la Grace Leibniz speaks of “composite substances” while in the Monadologie he only speaks of “composites”. The difference is puzzling. In the Monadologie Leibniz is typically taken to be presenting a strictly monadological metaphysics according to which simple substances are the only finite substances. Bodies exist and animals exist, but they are not substances (roughly speaking he thinks that an animal is a dominant monad and its organic body, which is itself an aggregate of monads). A number of texts suggest that neither bodies nor animals are true unities, and only a true unity (an unum per se) can qualify as a substance, strictly speaking. Any reality that bodies and animals possess is in some way derivative of the reality of simple substances. The obvious puzzle is that Leibniz speaks of simple and composite substances in the Principes de la Nature et de la Grace. What are we to make of these seemingly divergent claims?