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.

Gottlob August Tittel (1739–1816) was a professor at a Gymnasium in Karlsruhe and is best known as an early critic of Kant’s theoretical and practical philosophy. This chapter contains selections from his On Herr Kant’s Reform of Moral Science (1786), the first book-length commentary on the Groundwork. In this text, Tittel makes several important objections to the Groundwork, many of which have since become classic, such as: that the categorical imperative is empty, that the motive of duty for duty’s sake is impotent in human nature, and that Kant is a covert consequentialist. Tittel’s most famous objection, however, is that the categorical imperative is not a new principle of morality, but merely a new formula of a principle philosophers have known for a long time. Kant was aware of the Reform, and he responds to Tittel in a footnote in the Preface to the second Critique (see 5:8.28–37n).

Pistorius’ review of the Groundwork was without a doubt the most important early review, at least with respect to its influence on the second Critique. Pistorius raises several important objections in the review, many of which are now regarded as classic responses to Kant’s moral theory in the literature. These include: the empty formalism objection, the claim that Kant is a covert consequentialist, that only hypothetical imperatives can bind human beings, and that there is a distinction to be made between happiness through instinct and happiness through reason. Kant was aware of the review and responds to Pistorius explicitly in the second Critique, such as in the second chapter of the Analytic, where he replies to a “certain reviewer,” i.e., Pistorius, who claimed against the Groundwork that “the concept of the good was not established before the moral principle.” (5:8.27–9.2)

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.