Kant did not initially intend to write a Critique of Practical Reason, let alone three Critiques.Footnote ¹ When the first edition of the Critique of Pure Reason was published in May of 1781, it was meant to be “a critique of the faculty of reason in general” (Axii), and thus a critique of both theoretical and practical reason, and which was thereby meant to function as a “propaedeutic” or preparation for both “the metaphysics of nature as well as of morals” (A850/B878, see also A841/B869). This is also how Kant conceived of the project carried out in the first Critique in the decade prior to its first publication,Footnote ² and it is how he continued to see things during the first few years that followed. We learn from Kant’s correspondence, for instance, that his next main focus after the first Critique was not any additional Critique, but the ‘Metaphysics of Morals,’ a project he had announced to have been working on for years already.Footnote ³ Kant’s plans eventually changed, of course, and the Critique of Practical Reason was published in late 1787, with 1788 on the title page. What happened in the intervening years that caused Kant to decide to write a Critique of Practical Reason? In the following introduction, which has been kept brief intentionally so as to save as much space as possible for the translations that follow, I outline some of the major events in Kant’s development during this period and highlight just one important factor that encouraged him to write the second Critique. As we will see, the story of the Critique of Practical Reason’s origin reveals that it is especially suited to being accompanied by certain background source materials that help illuminate its aims and contents.Footnote ⁴

The initial reception of the Critique of Pure Reason was disappointing. Kant’s ideal commentators, Johann Nicolaus Tetens and Moses Mendelssohn, had little or nothing to say about the book,Footnote ⁵ and the only reviews that appeared during the entirety of 1781 were just three short announcements and summaries.Footnote ⁶ So Kant somewhat quickly, namely by the fall of 1781 at the latest,Footnote ⁷ set to work on a popular version of the Critique that would make its contents more accessible, a work which eventually became the Prolegomena.Footnote ⁸ While he was working on this project, the first serious review of the Critique of Pure Reason came out on January 19, 1782, in the Zugabe zu den Göttingischen Anzeigen von gelehrten Sachen.Footnote ⁹ Originally published anonymously but later revealed to have been written by Christian Garve and edited by Johann Georg Heinrich Feder, the review claimed, among other things, that Kant’s transcendental idealism was no different than Berkeley’s idealism.Footnote ¹⁰ Kant was upset by the review and publicly responded to it in the Prolegomena (see 4:372–80 as well as 4:288–94). Unfortunately, the Prolegomena seems to have done little to make Kant’s philosophy more intelligible; as Kant’s future colleague Johann Schultz put it: “it almost appears as if one recoils before the Prolegomena only slightly less than one does before the Critique” (1784, p. 6). Indeed, the initial reception of the Prolegomena must have been disappointing too, for it gained only slightly more attention than the first Critique: after it appeared in the spring of 1783,Footnote ¹¹ it received four short announcements in 1783, only two longer reviews in 1784, and then one review each in 1785 and 1786.Footnote ¹²

While all of this was taking place, Kant was still working on the Metaphysics of Morals.Footnote ¹³ In the fall of 1783, an important event happened that altered the subsequent development of that text, namely the publication of Garve’s German translation of Cicero’s De officiis (On Duties) as well as Garve’s accompanying three-volume Philosophische Anmerkungen und Abhandlungen zu Cicero’s Büchern von den Pflichten (Philosophical Remarks and Treatises on Cicero’s Books on Duties). As we learn primarily from the correspondence of Kant’s close friend Johann Georg Hamann, Kant considered writing an “anti-critique” to Garve and his characterization of Cicero in early 1784, and this might have even been meant as an indirect reply to Garve’s review of the first Critique.Footnote ¹⁴ This eventually evolved into a “prodromus” or forerunner to the Metaphysics of Morals, however, which no longer contained any references to Garve or Cicero whatsoever,Footnote ¹⁵ and which Kant was still working on in August 1784.Footnote ¹⁶ The book Kant completed soon after was the Groundwork of the Metaphysics of Morals, which was sent to the printer in September of 1784 and published in April 1785.Footnote ¹⁷

The Groundwork comprises an important stage in the development towards the second Critique, because in it we find Kant using the expression ‘critique of pure practical reason’ for the very first time in any of his writings, whether published or unpublished. Furthermore, Kant now contrasts a ‘critique of pure speculative reason’ with a ‘critique of pure practical reason,’ and claims that the latter serves as the foundation for the metaphysics of morals, just as the former serves as the foundation for the metaphysics of nature (4:391.18–20). This is a clear shift from his earlier view that one critique of the faculty of reason in general is sufficient preparation for both. Nevertheless, even at the time of the Groundwork’s publication, Kant did not intend to write a separate book entitled Critique of Practical Reason, nor did he intend to fully carry out a critique of this sort, whether as part of the Groundwork or otherwise. As Kant explains in the Preface to the Groundwork:

Indeed, later in the Groundwork Kant claims that, to the extent that such a critique of pure practical reason is necessary for his purposes, this is accomplished in Section III (see 4:445.11–15). Thus, once the Groundwork is finished, Kant does not turn his focus to a more complete version of the ‘critique of pure practical reason,’ but says that “I am proceeding immediately with the full composition of the Metaphysics of Morals.”Footnote ¹⁸

In the spring of 1786 Kant begins to work on the second edition of the Critique of Pure Reason at the request of his publisher.Footnote ¹⁹ It was while working on the B edition of the first Critique that Kant seems to have re-evaluated the need to undertake a more complete critique of pure practical reason, for in November of 1786 Kant published the following announcement in the Allgemeine Literatur-Zeitung, a somewhat recently founded pro-Kantian journal:

When the B edition was finally published in April of 1787, it did not contain the advertised ‘critique of pure practical reason.’ Already in June of 1787, however, Kant tells Christian Gottfried Schütz that he is “so far along with my Critique of Practical Reason that I intend to send it to Halle for printing next week” (10:490.12–14). This was ambitious, for it was not until September of 1787 that the book was actually in Halle for printing,Footnote ²¹ and it was not published until December of 1787 because J.F.A. Grunert, Kant’s printer in Halle, wanted to print it with new, sharp letters.Footnote ²²

To summarize the story so far: Kant made significant changes to the plan of his Critical philosophy more than once over the span of just a few years. While in 1781 he conceived of the one Critique of pure reason as sufficient preparation for both the metaphysics of nature and of morals, as of the Groundwork’s completion in the fall of 1784 at the latest he came to think that the metaphysics of morals at least in principle required a critique of pure practical reason, even if he simultaneously thought that it was unnecessary to completely carry out such a critique at the time.Footnote ²³ While he was working on the second edition of the first Critique in 1786, however, he changed his mind again and came to realize that carrying out a critique of pure practical reason in full was necessary after all, but he planned to include it in the second edition of the first Critique. Finally, sometime between November 1786 and April 1787Footnote ²⁴ he decided to publish it as a separate book and, as we learn from the work itself, it is no longer a ‘critique of pure practical reason,’ but a critique of reason’s entire practical faculty, whose aim is to show “that there is pure practical reason” (see 5:3.6–7). The questions that I want to briefly address in the remainder of what follows are: what was it that made Kant decide that a full critique of practical reason was necessary, that is, one that went beyond what was already accomplished in Groundwork III, and why did he decide to publish it as a separate book?

Kant likely decided to publish the Critique of Practical Reason as a separate book for pragmatic reasons: the first Critique was already quite long, for instance, and he probably wanted to avoid delaying the publication of the second edition any longer than was absolutely necessary.Footnote ²⁵ That Kant ‘discovered’ the a priori principles of the faculty of feeling during this same timeframeFootnote ²⁶ also might have motivated him to reserve a separate work for each of the three fundamental faculties. The more interesting question, however, is why he decided to carry out a more substantial critique of (pure) practical reason at all. This is a complicated question, and to fully answer it we would also need to consider Kant’s allegedly different approaches to the deduction of freedom and morality in the Groundwork and the second Critique,Footnote ²⁷ as well as his ‘discovery’ of the antinomy of pure practical reason,Footnote ²⁸ to name just two of the most important advances made in the second Critique. The factor that I want to focus on for the purposes of this volume, however, is the role played by Kant’s early critics and reviewers.

As has already been seen in the above ‘Announcement,’ the revisions Kant made to the second edition of the first Critique were at least in part intended to prevent any further misunderstanding of the text.Footnote ²⁹ Kant’s correspondence confirms that correcting misunderstandings and responding to his critics were indeed major concerns of his both in revising the first Critique and when writing the second. In a letter to Johann Bering from April 7, 1786, for instance, Kant says that in the revised edition of the first Critique he will “attend to all the misinterpretations and misunderstandings that have come to my attention since the book began circulating.”Footnote ³⁰ Additionally, in a letter to Ludwig Heinrich Jakob from around September 11, 1787, Kant says that: “My Critique of Practical Reason is at Grunert’s now. It contains many things that will serve to correct the misunderstandings of the [Critique of] theoretical [reason]” (10:494.13–15). Indeed, even after he decided to publish the Critique of Practical Reason as a separate book, Kant is clear in several places that the second Critique will serve to clarify views he presented in the first Critique.Footnote ³¹

But it was not only the objections to and misunderstandings of the first Critique, and perhaps also the Prolegomena, that concerned Kant at this time. On the contrary, he must have been seriously concerned about the things that were being said about the Groundwork as well. In the above ‘Announcement,’ for instance, Kant claims that the ‘critique of pure practical reason’ that he intended to include in the B edition was in part meant to “defend” his principle of morality “against the objections that have been made and are still to be made.” In fact, it was likely the reactions to the Groundwork in particular that played an instrumental role in bringing Kant to realize that he needed to carry out a more complete critique of (pure) practical reason beyond what he had already accomplished in the Groundwork, for in contrast to the disappointing initial reception of both the first Critique and the Prolegomena, the Groundwork was fervently reviewed immediately after it was first published. As can be seen from the following, roughly chronological list,Footnote ³² the Groundwork was reviewed no less than twelve times within the first eighteen months or so after it was available:

1. 1. Allgemeine Literatur-Zeitung. Number 80. Thursday, April 7, 1785, pp. 21–23. (Landau Reference Landau1991, pp. 135–39)

2. 2. Gothaische gelehrte Zeitungen. 66. Stück, August 17, 1785, pp. 533–36; 67. Stück, August 20, 1785, pp. 537–44; Supplement to 67. Stück, August 20, 1785, pp. 545–50. (Landau Reference Landau1991, pp. 183–97)

3. 3. Denkwürdigkeiten aus der philosophischen Welt. Edited by Karl Adolph Cäsar. Erster Jahrgang. 3. Stück/Quartal, Summer/Fall 1785, pp. 433–67. (Landau Reference Landau1991, pp. 203–18)

4. 4. Altonaischer Gelehrter Mercurius. 37. Stück, September 15, 1785, pp. 291–95. (Landau Reference Landau1991, pp. 219–22)

5. 5. Neueste Critische Nachrichten. 11. Band, 40. Stück, October 1, 1785, pp. 314–16. (Landau Reference Landau1991, pp. 223–25)

6. 6. Göttingische Anzeigen von gelehrten Sachen. 172. Stück, October 29, 1785, pp. 1739–44. (Landau Reference Landau1991, pp. 229–33)

7. 7. Tübingische gelehrte Anzeigen. 14. Stück, February 16, 1786, pp. 105–12. (Landau Reference Landau1991, pp. 277–83)

8. 8. Kritische Beyträge der neuesten Geschichte der Gelehrsamkeit. 1. Band, 1. Stück, 1786, pp. 202–13. (Landau Reference Landau1991, pp. 318–23)

9. 9. Russische Bilbiothek, zur Kenntniß des gegenwärtigen Zustandes der Literatur in Rußland. 10. Band, 1–3. Stücke, 1786, pp. 165–66. (Landau Reference Landau1991, p. 325)

10. 10. Allgemeine deutsche Bibliothek. 66. Band, 2. Stück, May 1786, pp. 447–63. (Landau Reference Landau1991, pp. 354–67)

11. 11. Altonaischer Gelehrter Mercurius. 23. Stück, June 8, 1786, pp. 177–79. (Landau Reference Landau1991, pp. 403–404)

12. 12. Allgemeine Literatur Zeitung. Number 259, Monday, October 30, 1786, columns 193–98; Number 260a, Tuesday, October 31, 1786, columns 201–208; Number 267, Wednesday, November 8, 1786, columns 265–72. (Landau Reference Landau1991, pp. 450–69)

Kant was aware of many of these reviews, including number 6, authored by J.G.H. Feder, the editor of the Göttingen review; number 7, authored by J.F. Flatt; and number 10, authored by H.A. Pistorius, as I explain in the Introductions to Chapters 8, 3, and 6 respectively. The majority of these reviews were critical, thus Daniel Jenisch’s statement to Kant from May 14, 1787, can likely be generalized: “Your Groundwork [Grundlage] of the Metaphysics of Morals, my Herr Prof., has found incomparably more opposition among my scholarly acquaintances than your Critique” (10:486.24–26). Similarly, Jakob reports to Kant on July 17, 1786, that “the misunderstanding concerning your [Groundwork of the] Metaphysics of Morals seems to be far greater than that concerning your Critique” (10:462.6–7).

To be sure, the reviews of the first Critique and the Groundwork were certainly not the only things on Kant’s mind at the time and which contributed to him deciding to write the Critique of Practical Reason. The first ever book-length commentary on the Critique of Pure Reason, namely Johann Schultz’s Erläuterungen über des Herrn Professor Kant Critik der reinen Vernunft (Elucidations of Herr Professor Kant’s Critique of Pure Reason), was published during this period, as was the first book-length commentary on the Groundwork, i.e., Gottlob August Tittel’s Über Herrn Kants Moralreform (On Herr Kant’s Reform of Moral Science). Kant knew of both these commentaries, as I explain in the Introductions to Chapters 4 and 5. The pantheism controversy was also raging at the time, and Kant finally decided to enter it in October of 1786 with his ‘Orientation’ essay, which itself received a critical response in early 1787 by Thomas Wizenmann. As I note in the Introduction to Chapter 7 below, Wizenmann is the only one of Kant’s critics mentioned by name in the second Critique. This is all in addition, of course, to the ‘misunderstandings’ of the first Critique that the second Critique was meant to correct, as mentioned above.

Taking all of this together, it is hardly surprising that the Critique of Practical Reason is a somewhat unique work in Kant’s corpus in that it addresses earlier reviews, reactions, and criticisms more so than any other, whether explicitly or implicitly.Footnote ³³ In the Preface alone, for instance, Kant makes several explicit references to previous reviewers and objections.Footnote ³⁴ It is therefore beyond question that the early reactions to Kant’s philosophy were instrumental in his decision to write a full-blown Critique of Practical Reason that goes beyond that contained in the Groundwork. This is the case to such an extent that, as Heiner Klemme has claimed: “It is possible that there might not have been a second Critique in the form that we know it without the external criticisms that were levelled against his philosophy.”Footnote ³⁵ As such, the Critique of Practical Reason is especially well suited to being accompanied by certain background source materials that help illuminate its aims and contents, by way of illustrating the views and criticisms that he was reacting to. The chapters of this volume collect only the most essential of these materials, and in most cases they make them available in English for the very first time.

The following eleven chapters, which have been organized chronologically by first publication date, are not limited to the period between the publication of the first and second Critique but are divided into three parts to indicate three distinct ways in which the selections serve to place the second Critique in historical context. In Part I, ‘Pre-Kantian Moral Philosophy,’ I have included selections from the ethics textbooks written by Christian Wolff and Christian August Crusius, arguably the two most important moral philosophers writing in German during the eighteenth century prior to Kant. These first two chapters represent two diverging approaches to moral philosophy, with which Kant was familiar and with which he engages in all his major ethical works, including the second Critique. In Part II, ‘Between the Critiques,’ which is the most substantial part of the volume, I offer five translations: reviews of the Groundwork written by Flatt and Pistorius, Pistorius’s review of Schultz’s Elucidations, selections from Tittel’s first commentary on the Groundwork, and Wizenmann’s reply to Kant’s ‘Orientation’ essay. These are all profoundly important as background source materials because Kant was aware of and responds to them all at various points in the second Critique. In Part III, ‘The Reception of the Critique of Practical Reason,’ I have translated three reviews of the second Critique, namely those authored by Feder, August Wilhelm Rehberg, and Pistorius, as well as a selection from Garve’s essay Über die Geduld (‘On Patience’), which collectively offer a diverse insight into the early reception of the second Critique. In some cases, such as the selection by Garve, Kant was familiar with the text and responds to it in later works. I explain details such as these in the Introductions that precede each chapter, wherein I also briefly sketch the life and works of the author, indicate the relevance of the translated text for the second Critique, as well as provide an overview of the text’s key points. To be noted is that the Introductions intentionally refrain from providing a full-scale analysis of each text, nor do they offer an exhaustive list of where Kant might have engaged with them. It is rather my hope that these translations speak for themselves and inspire readers to find connections that have not yet been discovered.