Paul Guyer: Kant’s Impact on Moral Philosophy. Oxford: Oxford UniversityPress, 2024. ISBN: 9780199592456.

Paul Guyer claims that he would “be very happy” if his Kant’s Impact on Moral Philosophy “were seen as carrying on from where Schneewind left off in his great book The Invention of Autonomy, which told the history of modern moral philosophy up to and through Kant” (ix). Schneewind presented us with an origin story of autonomy. A sequel is a risky thing. Some of the very worst products of the human mind are sequels, and few of the best ones are. Fortunately, Guyer’s book falls under the rare Empire Strikes Back category of sequels. It exists for good reason, and we should be glad that it does.^[1] I stand in awe of the sheer breadth and depth of the material Guyer covers. He has worked through an incredible amount of primary and secondary texts and manages to tell a compelling narrative about how various German, British and American philosophers of the last 200 years followed Kant, criticized him, departed from him and yet often remained committed to some of his most fundamental insights. In doing so, he goes far beyond familiar territory in terms of both primary authors and secondary sources.

The book opens naturally with an extended summary of Kant’s moral philosophy, which sets the scene for the discussion of Kant’s impact on his contemporaries, successors, and critics. Guyer then turns to critical replies to Kant by his contemporaries, as well as to Kant’s impact on Classical German philosophy (in a broad sense including, e. g., Nietzsche), and finally to the anglophone reception of Kant in the US and the UK, including contemporary figures such as Christine Korsgaard, Adrian Piper and Barbara Herman. There are two important limitations of the focus of Guyer’s book: it lacks a detailed discussion of Kant’s philosophy of right and political philosophy, as this discussion will be undertaken by Howard Williams as a separate project. Moreover, the book does not cover Neo-Kantianism or critical theory, nor Kant’s reception in countries other than Germany, the US, and the UK. Given that the work as it is already consists of more than 600 pages, there is an obvious reason for these limitations.^[2]

In what follows, I will first direct prospective readers’ attention to a few points that I consider to be highlights – this is admittedly partly guided by my personal preferences and interests – and then zone in on some of Guyer’s notable interpretative choices.

Guyer structures the early reception of and critical responses to Kant around a number of themes, representative of “many of the issues with Kant’s position that have occupied philosophers ever since” (113). The most significant of these are the roles of universal happiness, freedom, and emotions. As someone who is interested in Kant not purely as a figure from the history of philosophy but also systematically, I appreciate this structure of the historical material, and I suspect others will too.

One admirable feature of the work throughout is that Guyer takes seriously the moral philosophical thoughts of the figures he engages with, including those now better remembered as metaphysicians (Schelling) or Kant commentators (Paton). Guyer offers novel and thought-provoking spins on a number of historical figures and their relationship to Kant. To give just one example, he argues that Sidgwick’s method has underappreciated parallels to Kant’s. Sidgwick wanted to base his investigation on self-evident insights rather than empirical generalizations. Focusing on the latter was typical for the utilitarians of his time, whereas focusing on the former can be seen as a Kantian alternative (428). Thus, the very method of the Methods of Ethics was more Kantian in spirit than many assume.

Finally, I thought that the extensive discussion of attempts to unify Kantian moral philosophy and consequentialism (e. g., Hare, Cummiskey, Parfit) is of great value, since this is a topic that many orthodox Kantians might shy away from given the paradoxical, if not outright offensive, ring that “Kantian consequentialism” has to many ears. The impression that readers of Guyer’s book will get from this discussion is that Kant may have been even more significant than hitherto acknowledged. This is especially so for thinkers who made a point of abandoning what they considered to be Kantianism. These thinkers would have done well to acknowledge and explore their Kantian roots. In fact, one of the leitmotivs of Guyer’s book is how those who critically reacted to Kant were more influenced by Kant, and sometimes even more Kantian, than they themselves admitted.^[3] This, I take it, will make for a compelling narrative for many Kantians who may have already suspected as much with regard to some of the figures Guyer covers. Guyer’s book will provide them with plenty of ammunition and a narrative to vindicate Kant’s enduring significance to a diverse array of thinkers and philosophical traditions.

I am sure respective experts on one of the more than 40 thinkers Guyer covers will find bones to pick, as is inevitable for a work that covers such a breadth of material and thinkers. The most significant of these will naturally concern the reading of Kant himself that Guyer puts forward. After all, this reading underlies many of his claims about the impact Kant had, especially on those who seemingly departed from him yet remained committed to what Guyer deems to be core Kantian insights, as well as on Kant’s ability to successfully reply to criticism.

The reading of Kant that Guyer proposes will be familiar from other works of his, yet Kant’s Impact is a particularly instructive source for a statement of this view. Guyer presents the big picture underlying his book as follows:

The reception of Kant’s moral philosophy has been divided from the outset between those who find the gist of it in Kant’s conception of moral law, or in the idea that the requirement of the universalizability of maxims is not just a necessary but also the sufficient condition for both the determination and the establishment of all our moral duties, and those who find the core of Kant’s moral philosophy in his idea of humanity as the freedom of each human being to set his or her own ends, with the task of morality being then to determine the conditions under which the maximum freedom of each can be reconciled with the equal freedom of all, the Formula of Universal Law in turn being intended as a method for accomplishing this goal. (497)

Guyer’s own sympathy is clearly with the latter reading. Freedom for him functions as a value that underlies Kant’s formal principles. Guyer is by no means alone in making assumptions of this type, either historically or in contemporary Kantian ethics.^[4] Yet the idea that it is the responsibility of individuals (and maybe also of institutions) to bring about a maximum of this value (within certain constraints) is quite unusual within Kantian ethics and certainly within Kant scholarship.

Much evidence for this reading stems from pre-critical lecture notes and late works, not from the Groundwork or the Critique of Practical Reason, the works that enjoyed the most attention from Kant’s contemporaries and following generations of philosophers. Guyer stresses the continuity between early lecture notes and elements of the Groundwork. He argues that humanity in the Groundwork is what Kant calls freedom in the earlier lecture notes. Thus talk about humanity in Kant’s published writings should be understood as talk about freedom. Accordingly, the Formula of Humanity should be understood as concerned with freedom of choice as the essential end of human beings (57–58). Morality then requires us to promote equal freedom, the capacity to set and pursue one’s ends, for all humans.

According to Guyer, Kant’s published works do not always spell out with sufficient clarity some of the central ideas Kant shared with his critics, specifically concerning the role of freedom as something to be promoted. As a result, some of the eminent figures in the post-Kantian history of philosophy did not think of themselves as Kantians when they were indeed much closer to Kant than they themselves (and we) believed. Obviously, one may also wonder whether Kant perhaps did in fact express his views most clearly in his published writings, such that his views differ more from those of his successors than Guyer suggests. This is an exegetical question about which reasonable people may (and I suspect will) disagree. I shall leave it at that and focus on the philosophical content of Guyer’s interpretation.

I think that the philosophically most interesting theme running through Guyer’s book is the relationship between Kant and consequentialism.^[5] It is one of the particular merits of Guyer’s book that he tackles the issue without regard for the usual divisions between ethical theories that may unduly constrain our understanding of the role or value of humanity and freedom and the attitudes we are to take toward these goods.

However, I think that Guyer’s relatively sympathetic discussion of Kantian consequentialisms may come at the expense of essentially turning Kant into someone who is a non-standard consequentialist. Guyer stresses that his reading of Kant is not consequentialist, as working toward the greatest possible freedom for all is “not what anyone usually means by consequentialism” (44). He is right that this is not a form of consequentialism in its most well-known sense – maximizing utilitarianism – or in many other senses. The good we are to promote, according to Guyer, is freedom, not pleasure, and we are not to promote an aggregate good to the detriment of some whose rights may be infringed for a supposed greater good. Thus, Kant avoids some of the most pressing problems of consequentialism, such as the problem that we may be permitted, or even required, to instrumentalize a person if this increases the sum total of freedom (8).

Yet Guyer does seem to read Kant as a non-standard consequentialist who thinks that we ought to promote a non-standard good, namely equal freedom. It may well be the case that the most plausible reading of Kant, and maybe even the most plausible ethical theory simpliciter, is consequentialist in a wide or non-standard sense, and we should not get too hung up on whether something can be labeled “consequentialist” in some sense. Yet, we should worry that some well-known problems of consequentialism still apply to a view that has us promote equal freedom for all.

There are a number of uncontroversial ways in which Kant requires us to promote freedom if this includes certain material conditions that impact the pursuit of people’s ends. Presumably, the duty of beneficence requires wealthy people to aid those less fortunate than they are.^[6] A Kantian analysis of this could be that those living in material deprivation cannot exercise their freedom effectively as they lack the means to pursue their ends sufficiently.^[7] However, Guyer insists that the promotion of freedom must be a form of maximization: “the moral law, or its specification in the form of the various duties of human beings, is aimed at the maximization of human freedom,” albeit “for each compatible with the greatest possible equal freedom for all” (8). Maximization of any kind is a strong and demanding attitude toward a good, and the idea that we are to maximize, even in a non-standard sense, is alien to the Kantian framework. Yet the interpretative assumption that Kant wants freedom to be maximized (equally for all) also allows Guyer to reveal hitherto unrecognized parallels with philosophers of a consequentialist leaning and thus does quite a bit of work for Guyer’s overall narrative.

At the very least, maximization raises a number of difficult questions: are we morally required to do as much as we possibly can in order to promote everyone’s equal freedom? If not, when and why would it be permissible and rational to stop? It may well be that by depriving myself (or someone else) of the freedom everyone is to enjoy I make a number of other people freer,^[8] and as a result freedom is enjoyed more equally (even with my or someone else’s now being less free than before). It seems that people who are to maximize equal freedom would be required to make this sacrifice or that at the very least there is a substantive burden to justify their doing less. Guyer clearly wants to avoid problems of this kind, but his emphasis on maximization runs counter to this endeavor. I find Guyer’s reading intriguing, systematically more so than as a historical account of Kant’s ethics, but I want to understand it better, in particular how such a reading can avoid the known shortcomings of ethical theories that require maximization.

Given Guyer’s problem-centered narrative of Kant’s impact on his contemporaries, there would have been an organic way for Guyer to introduce the theme of demandingness explicitly and thereby address some of the questions that maximization raises: Like some other critical contemporaries of Kant, Maria von Herbert (1769–1803), whom Guyer does not mention, raised the problem of the demandingness of Kant’s ethics. A discussion of demandingness is, among other things, a discussion of how much morality can reasonably require of us and whether there are limits to duty. In a now (in)famous exchange of letters with Kant, von Herbert interestingly claims that Kantian ethics is too easy for her, since she does not have inclinations that counteract duty. She thus criticizes Kant for underdemandingness. Von Herbert here is in stark contrast to a number of other contemporaries of Kant, such as Schiller and philosophers of the generation after Kant, most significantly Hegel, as well as some current figures who stress the allegedly unreasonable demandingness of Kantian ethics. These philosophers argue(d) that Kantian ethics supposedly requires us to act without regard to our inclinations, or to purposefully act against them, and to achieve rational ideals in an empirical and imperfect world.^[9] Mentioning von Herbert’s exchange with Kant could have functioned as a segue for a discussion of the over- (and under)demandingness charges leveled against Kant by his contemporaries and thereafter. This would have been historically illuminating. It would also have served well to further help readers understand the nuances of the reading of Kant on which Guyer rests his grand narrative, and specifically to clarify Guyer’s crucial notion of maximization and its philosophical viability.

Questions about maximization notwithstanding, The Impact of Kant’s Moral Philosophy is a worthy successor to the Invention of Autonomy. Guyer pushes far beyond the usual narrative according to which Kant’s greatest impact was on the German Idealists and Rawls(ians). His book will be of great interest to Kant scholars and Kantian ethicists, as well as to scholars who are curious about the Kantian debts of many significant 19th- and 20th-century ethicists.^[10]