 Leibniz assumes that all events have causes—they do not just happen—and typically considers only three theories of causation worthy of philosophical consideration: physical influx, occasionalism, and parallelism. Interestingly, Leibniz excludes from this list Spinoza’s aspect theory of causation. For it is apparent that Leibniz thinks that any view that entails the existence of one and only one genuine substance can not even begin to offer a proper theory of causation. Let’s summarize in turn each of the theories that Leibniz does take seriously.