 So, to summarize, what causes the changes in perceptions? Three species of cause: efficient causes (in accordance with laws of mind and active forces), final causes (in accordance with the law of appetites and ultimately God’s aim of universal and maximum harmony), and formal causes (in accordance with the Law of Continuity). Leibniz’s account of intrasubstantial causation therefore involves a tight connection between efficient, final, and formal causes. This should not be surprising, since Leibniz tells us that “[a] cause in the realm of things corresponds to a reason in the realm of truths, which is why causes themselves—and especially final ones—are often called reasons” (New Essays A vi, 6, 475).