Hardly any attempt to come to grips with the classical problem of free will and determinism directly addresses the metaphysical vision driving the concerns of those who believe that a significant sort of free will cannot exist in a deterministic world. According to this vision of such a world, all events, including human decisions and actions, take place as they must because the world is governed by necessity. Most philosophers who believe that free will is possible in a deterministic world ignore this root position, often regarding it as sufficient to cite considerations about moral responsibility, human agency, or the prerequisites for a society. Bernard Berofsky addresses that metaphysical picture directly. Nature's Challenge to Free Will offers an original defense of Humean Compatibilism. A Humean Compatibilist bases the belief in the compatibility of free will and determinism on David Hume's view that laws do not affirm the existence of necessary connections in nature. Berofsky offers a new formulation of Hume's position, given that, until now, there has been no acceptable version. His conclusion that free will is compatible with determinism is based as well upon a defense of the existence of psychological laws as autonomous relative to physical laws. He rejects appeals to the unalterability of laws (as in the Consequence Argument) on the grounds that this principle fails for psychological laws. Efforts to bypass this result by trying to establish that all laws are reducible to physical laws or that psychological states supervene on physical states are shown to fail. Berofsky concludes that the existence of free will as self-determination together with the power of genuine choice is not threatened even if we live in a deterministic world.