Editing Critique of Practical Reason (section)

==Dialectic: Chapter Two==
Kant posits two different senses of "the highest good." On one sense (the ''supreme''), it refers to that which is always good and which is required for all other goods. This sense is equivalent to "dutifulness". In another sense (the ''perfect''), it refers to the best of good states, even if part of that state is only contingently good. In this latter sense, the highest good combines virtuousness with happiness.<ref>Kant, KpV 5:110</ref>

The highest good is the object of pure practical reason, so we cannot use the latter unless we believe that the former is achievable. However, virtue obviously does not necessarily lead to happiness in this world and vice versa. To aim at one is not to aim at the other and it seems to be a matter of chance whether the rest of the world will fill in the gap by rewarding us for our virtuous behavior.

But Kant's solution is to point out that we do not only exist phenomenally but also noumenally. Though we may not be rewarded with happiness in the phenomenal world, we may still be rewarded in an afterlife which can be posited as existing in the noumenal world. Since it is pure practical reason, and not just the maxims of impure desire-based practical reason, which demands the existence of such an afterlife, immortality, union with God and so on, then these things must be necessary for the faculty of reason as a whole and therefore they command assent.

The highest good requires the highest level of virtue as the supreme moral condition for being worthy of happiness. We can know by self-examination that such virtue does not exist in us now, nor is it likely to exist in the foreseeable future. In fact, the only way in which the fallible human will can become similar to the holy will is for it to take an eternity to achieve perfection. Therefore, we can postulate the existence of immortality. This postulate allows us to conceive how it is possible for us in some way to achieve a will that is completely adequate to the moral law, viz., a will similar to the holy will. If we do not postulate it, we will be led to either soften the demands of morality in order to make them achievable here and now or we will make the absurd demand on ourselves that we must achieve the holy will now.<ref>Kant, KpV 5:122-123</ref>

The highest good also requires the highest level of happiness, in order to reward the highest level of virtue. We therefore need to postulate that there is an omniscient and omnipotent God who can order the world justly and reward us for our virtue. However, this does ''not'' mean that God is to be the ''basis'' for our moral action. Rather, this postulate of God's existence gives us a way to understand ''for a practical aim'' how the highest level of happiness proportionate to the highest level of virtue could be ''possible''.