The final chapter addresses the question of what Kant should have said in reply to Constant’s challenge. The objections of his readers and interpreters should be taken seriously as expressions of ordinary moral consciousness; and it is true that moral restrictions can leave us feel helpless in the face of evil. But these considerations would not have been sufficient to change Kant’s mind. So, should his rigorous opposition to untruthfulness count against his moral philosophy? It is argued that Kant’s absolutism is less problematic than it seems, partly because most – if not all – realistic reconstructions of Constant’s case leave us with more promising practical options than lying, partly because Kant’s moral theory contains certain resources that mitigate his absolutism, for example, his conception of the Highest Good. The question of whether his ethical prohibition of lying as a violation of a duty to self is justified is left unanswered.

Kant presents his conception of the highest good as steering a path between Epicureanism and Stoicism. However, in spite of his differences with Stoicism, namely, his rejection of the ideal of the sage as unattainable for human beings and his insistence upon a conception of freedom of the will that is absent from the ancient doctrine, Kant’s position, especially in the 1790s, ends up being closer to original Stoicism than he recognizes, or at least lets on. Contrary to Kant’s interpretation, the Stoics did not reduce happiness to consciousness of one’s virtue, but allow for the pursuit of happiness as ordinarily conceived within the limits of nature – and so does Kant. Yet Kant’s later conception of the highest good as happiness to be realized in the natural history of the human species, thus in nature, is close to the Stoic doctrine. And, contrary now to some commentators, while Kant still thinks that the possibility of the highest good on this conception needs a theistic underpinning, this is definitely not a specifically Christian position, because it involves no salvific role for Christ.

This chapter situates Kant’s rejection of Stoic eudaimonism within his overarching anti-eudaimonist agenda. The chapter begins by emphasizing the importance of the Stoic tradition for Kant’s critical reception of ancient ethical theory. It then reconstructs the central commitments of ancient Stoic eudaimonism and of Christian Garve’s quasi-Stoic eudaimonism. Turning to Kant’s anti-Stoic argument in the Dialectic of the Second Critique, the chapter argues that the primary target of Kant’s error of subreption (vitium subreptionis) is the Stoic Seneca, specifically his account of joy (gaudium) as an accompaniment of one’s consciousness of virtuous activity. After reconstructing Kant’s argument in detail, the chapter offers a new way to understand its anti-eudaimonist implications: practical illusion leads the Stoic to rationalize and, ultimately, to disfigure the moral law. Even in their moral ardor – or, rather, propelled by it – the Stoic commits an error of self-love.

Christian Wolff (1679–1754) was a profoundly important philosopher during the eighteenth century. ‘Wolffianism,’ broadly defined as adherence to Wolff’s teachings, was taught and promoted at all the major German universities for decades. Kant was educated and began his career within an environment that was dominated by discussion between proponents of and opponents to Wolff’s philosophy. This chapter contains a complete translation of Chapter 1 of Part 1 of Wolff’s ‘German Ethics’ (1720), in which Wolff gives a general overview of almost all the core features of his ‘universal practical philosophy.’ The translation contained in this chapter therefore serves as a concise introduction to Wolff’s ethics in general, and one that is especially helpful for better understanding Kant’s explicit reference to Wolff’s principle of perfection in the second Critique (see 5:40), among other things.

The third and final review authored by Pistorius in this volume is his review of the second Critique. The review completes a fascinating exchange between Pistorius and Kant that begins with the former’s early review of Schultz’s Elucidations and the Groundwork, among others, continues with Kant’s responses to these reviews in the second Critique, and ends here with Pistorius’ review of the second Critique. In the review, Pistorius returns to some of the same points made in his previous reviews, such as the ‘priority of the good’ objection, the charge of empty formalism, and Kant’s conception of freedom. A major theme of the review is Pistorius’ inability to accept Kant’s distinction between the empirical and intelligible character of human beings, and other topics include a discussion of the highest good and Kant’s relationship to Stoic moral philosophy.

This chapter finds that Augustine self-consciously departed from Stoicism and Platonism (while remaining within eudaimonism) in finding that there were other natural objects of human beings’ eros-love besides the highest good. This finding leads to a new explanation of Augustine’s distinction between use and enjoyment and to a new explanation of his view that grief would be found not only in the lives of the vicious but in the lives of the virtuous as well.

This chapter asks whether Augustine criticised Stoicism and Platonism because he thought that there was something fundamentally flawed about the eudaimonist approach to ethics, or whether he criticised Stoicism and Platonism because he thought that these philosophies had insufficiently understood eudaimonism itself. It finds that the latter explanation is correct: in reaching this conclusion, this chapter establishes that Augustine defined virtue and vice, or sin, from within the eudaimonist tradition, making use of the ideas of love as eros and philia, and of the highest good, or summum bonum.

Famously, in the Canon of Pure Reason, Kant present a practical argument to the effect that our beliefs in God and immortality are justified. I argue that reading the Critique of Pure Reason as the doctrine of method of metaphysics provides a straightforward explanation of the systematic place of Kant’s practical argument in the Canon. Customarily, the relevance of the Critique for the practical part of metaphysics is restricted to proving the theoretical undecidability of God and immortality, but the Canon clearly goes beyond establishing that. According to its positive task as the doctrine of method of metaphysics, the Critique must establish that metaphysics can achieve ‘architectonic unity’. I argue that showing that this unity is possible for metaphysics requires showing that there is conceptual space for coherently accommodating our commitment towards the existence of God and immortality within it.

The 1786 review of Kant's Groundwork for the Metaphysics of Morals by Hermann Andreas Pistorius raised the objection that Kant's categorical imperative is an "empty formalism" that needs an antecedent conception of the good long before Hegel made the same charge in 1802.  Kant's explicit response to Pistorius in the Critique of Practical Reason is just to double-down on the priority of the right over the good.  However, I suggest that Kant's characterization of humanity as an end in itself as the "ground of a possible categorical imperative" in the Groundwork, on the one hand, and his account of the highest good as the complete object of morality in the second Critique, on the other, together provide a much fuller and satisfactory response to the "empty formalism" objection.

Kant’s moral argument for faith in God aims not at converting unbelievers but at offering those who believe a reason for principled assent to the existence of God on moral grounds. It is based on a rational connection between purposive action and assent that applies not only to religious belief but to many other purposes as well, such as what Royce called “loyalty to a lost cause.” The argument in the Critique of Pure Reason differs significantly from its presentation in later works. Kantian moral faith is in tension with Cliffordian evidentialism but not inconsistent with it, and the two together constitute the doxastic virtue lying between the twin vices of uncritical credulity and stubborn incredulity; together they enable us to avoid the complacencies of both despairing resignation and overconfidence.

Kant holds that the origin of our propensity to evil arises in connection with our unsociable sociability. The effective response to it, therefore, must also be social. We must leave the ethical state of nature and join with others in voluntary ethical community, where our shared ends, conceived as the highest good, under the legislation of a divine lawgiver will promote moral progress among human beings. The existing communities of this kind are churches and ecclesiastical faiths, which fall short of their religious vocation but can and should be reformed so as to live up to it. The relation of rational religion to revealed religion is therefore intended by Kant to be dynamic, with the interpretation of revealed religion enriching rational religion and the reform of revealed religion bringing rational and revealed religion into closer harmony, leading gradually toward the founding of the Kingdom of God on earth.