 The second widely shared assumption is that free will seems difficult to reconcile with what we know about the world. While this assumption is shared by the majority of early modern philosophers, what specifically it is about the world that seems to conflict with freedom differs from philosopher to philosopher. For some, the worry is primarily theological. How can we make sense of contingency and freedom in a world determined by a God who must choose the best possible world to create? For some, the worry was primarily metaphysical. The principle of sufficient reason—roughly, the idea that every event must have a reason or cause—was a cornerstone of Leibniz’s and Spinoza’s metaphysics. How does contingency and freedom fit into such a world? For some, the worry was primarily scientific (Descartes). Given that a proper understanding of the physical world is one in which all physical objects are governed by deterministic laws of nature, how does contingency and freedom fit into such a world? Of course, for some, all three worries were in play in their work (this is true especially of Leibniz).