 Probably the most influential versions of the moral argument for belief in God can be traced to Kant (1788 [1956]), who famously argued that the theoretical arguments for God’s existence were unsuccessful, but presented a rational argument for belief in God as a “postulate of practical reason.” Kant held that a rational, moral being must necessarily will “the highest good,” which consists of a world in which people are both morally good and happy, and in which moral virtue is the condition for happiness. The latter condition implies that this end must be sought solely by moral action. However, Kant held that a person cannot rationally will such an end without believing that moral actions can successfully achieve such an end, and this requires a belief that the causal structure of nature is conducive to the achievement of this end by moral means. This is equivalent to belief in God, a moral being who is ultimately responsible for the character of the natural world. Kant’s arguments will be discussed later in this article.