Abstract

Throughout his critical corpus, Kant holds that we have a duty to promote the highest good, or the union of perfect virtue with complete happiness. However, it is not well understood how this thesis follows from Kant's core moral theory, or indeed, whether it is even compatible with that theory. I argue that the moral necessity of the highest good can be justified by integrating the conception into Kant's mature moral psychology; specifically, I show that the theory of radical evil and the duty to promote the highest good are reciprocally related. That is, the fundamental ethical revolution of the heart required of fallen wills like our own amounts to the adoption of the highest good as our ultimate practical object. ;Kant's theory of moral religion arises from his conception of the highest good. For he argues that we can make the possibility of the highest good comprehensible to ourselves only through the postulation of God's existence and the immortality of the soul. According to Kant, such postulation does not amount to knowledge, and allows only of a practical use. I explicate this conception of a practical use of the postulates through the notion of rational faith as ethical defense. That is, because our evil disposition will exploit the epistemic empty space of the transcendent in ways that will construe the highest good as impossible, we are constrained to oppose such ethically corrosive conceptions by means of an affirmation of the transcendent conditions of the possibility of the highest good; namely, the immortality of the soul and the existence of God. I also demonstrate that Kant's account of the conditions of possibility of the highest good expands to embrace a philosophy of history; for the realization of the highest good will require the achievement of perpetual peace, whose possibility we may think through the notion of a teleologically directed human history