  The activity, or appetition, that Leibniz regards as characterizing the monads is intimately bound up with his Principle of Sufficient Reason. For Leibniz, a monad contains its whole history because each monadic state (except for those states—creation is paradigmatic of these—that are the result of divine causation) has its sufficient cause in the preceding state. In turn, the present state is the sufficient cause of all succeeding states. Despite this emphasis on the inherent activity of substance, Leibniz, like Spinoza, rejected the possibility of transeunt causation among substances. Monads are “windowless” and neither admit nor emit causal influence. Moreover, being thus windowless, monads can no more receive perceptions from the world than they can any other external causation. Rather, a monad’s perceptions are built-in at creation. By preestablished harmony, these perceptions perfectly align with the universe’s infinite monadic states. This entails that while there is no genuine transeunt causation at the monadic level, a kind of pseudocausation results from monads’ harmonized perceptions of each other as their respective appetitions convey them through successive changes. For Leibniz, causal relations thus reduce to logical relations in that every change in a substance follows from its concept.