 Leibniz believed that every phenomenon could be explained. His Principle of Sufficient Reason states that “nothing takes place without a sufficient reason; in other words,…nothing occurs for which it would be impossible for someone who has enough knowledge of things to give a reason adequate to determine why the thing is as it is and not otherwise.” Though not everything possible happens (and, therefore not everything that happens is necessary), everything that happens has a sufficient reason in an antecedent state of the world. God’s necessary existence is the only state of affairs that is caused and does not have a sufficient reason in an antecedent state. Not only does everything have a sufficient reason, but all phenomena and events, including celestial motions, the formation of plant and animal bodies, and the processes of life, are regulated by the laws of mechanics, as the movements of the hands are regulated in a watch (G 7:417–8).