 If Leibniz does not think that perceptions can function as efficient or productive causes, why does Leibniz even speak of later perceptions as natural consequences of earlier perceptions, if not causally? There seem to be two good reasons for this. First, there is a purpose or end guiding the unfolding of perceptions in each substance. The substance (or primitive power) acts efficiently in order to fulfill this end. Such an end may be called a final cause. Second, Leibniz wishes to ground his Law of Continuity—that all change in nature is continuous (i.e., in nature there are no gaps). This points to formal causation in substances. In other words, the picture we come away with in Leibniz is that a substance’s perceptions, representing final and formal causes, rationally determine that substance’s future states. The object of a perception is a final cause insofar as each perception specifies why certain states should be produced rather than others. Perceptions themselves are formal causes insofar as they specify the content of a substance’s future states.