 Kant’s version of the argument can be stated in different ways, but perhaps the following captures one plausible interpretation of the argument. Morality is grounded in pure practical reason, and the moral agent must act on the basis of maxims that can be rationally endorsed as universal principles. Moral actions are thus not determined by results or consequences but by the maxims on which they are based. However, all actions, including moral actions, necessarily aim at ends. Kant argues that the end that moral actions aim at is the “highest good,” which is a world in which both moral virtue and happiness are maximized, with happiness contingent on virtue. For Kant “ought implies can,” and so if I have an obligation to seek the highest good, then I must believe that it is possible to achieve such an end. However, I must seek the highest good only by acting in accordance with morality; no shortcuts to happiness are permissible. This seems to require that I believe that acting in accordance with morality will be causally efficacious in achieving the highest good. However, it is reasonable to believe that moral actions will be causally efficacious in this way only if the laws of causality are set up in such a way that these laws are conducive to the efficacy of moral action. Certainly both parts of the highest good seem difficult to achieve. We humans have weaknesses in our character that appear difficult if not impossible to overcome by our own efforts. Furthermore, as creatures we have subjective needs that must be satisfied if we are happy, but we have little empirical reason to think that these needs will be satisfied by moral actions even if we succeeded in becoming virtuous. If a person believes that the natural world is simply a non-moral machine with no moral purposiveness then that person would have no reason to believe that moral action could succeed because there is no a priori reason to think moral action will achieve the highest good and little empirical reason to believe this either. Kant thus concludes that a moral agent must “postulate” the existence of God as a rational presupposition of the moral life.