  The crucial idea is that the body will follow its own laws, the mind its own laws, and there will be no true influence between the two. The mind and body thus seem to constitute, as it were, worlds apart, as indeed Leibniz claims later when he explains the world in terms of monads, and these worlds apart are, according to Leibniz, unified solely by virtue of the correspondence of their actions and perceptions. Further, to these separate realms there will apply two distinct means of explaining the events of the world: we may explain things according to the final causes of the mind or according to the efficient causes of the body or of bodies in general. Thus, not only do the mind and body each seem to follow a different set of laws, but the world, according to Leibniz, can be described in terms of either set of laws.