This book argues that the Stoics invented the concept of moral duty. Its author, Jack Visnjic, opens by admitting that this was not his original intention. Like many others, he accepted the predominant view that the notion of moral duty is a modern invention often associated with Immanuel Kant. Visnjic’s original plan, he tells us, was simply to examine the prehistory of this modern notion. However, his research led him to the view that the standard account is false.
When I opened this book, I did so as a firm believer in the standard view. The Stoics were no moralists telling people what they ought to do. They had no categorical imperative, only what Kant would have called a hypothetical imperative: if you want to enjoy a good life, then live consistently with Nature, virtue, etc. Visnjic’s book, then, is a head-on challenge to a central assumption in my own understanding of Stoicism and ancient ethics more widely. I was inevitably curious yet sceptical.
The book is divided into six chapters. The first four chapters focus on the Stoics and in particular on the concept of kathêkonta (appropriate actions, duties) and methods of moral deliberation. The last two chapters deal with Kant.
The opening chapter considers the meaning of the word kathêkon. Visnjic argues that this word refers to something that is required or prescribed in a normative sense rather than something merely suitable. Proponents of the standard interpretation usually render this as “appropriate action” precisely in order to avoid any sense of prescription. In order to challenge this, Visnjic examines pre-Stoic uses of the term (relegated to an appendix; at p. 15 one has to jump ahead to pp. 139-52 and then back). He offers a detailed discussion of every instance of the term in extant pre-Stoic literature—Xenophon, Herodotus, Lysias, and temporal constructions in Demosthenes and Aristotle. In each case it is argued that kathêkon is used in a way that can only mean something binding or required. It refers to an obligation or duty that ought to be obeyed. If that is correct, then it would be decidedly odd—indeed perverse—for Zeno to select this term to express a central idea in his ethics only to use it in a quite different sense. The term had a normative force and that is surely why Zeno selected it: to develop an account of moral duty.
Where do these duties come from? The answer is straightforward: they come from Nature (p. 16). It is not merely appropriate that living beings pursue the things that will aid in their survival; it is prescribed by Nature that living beings will do this. The animal or human being that does not pursue its continued existence in this way has gone wrong. It is not doing what it ought to do. As human beings mature into rational agents, the same applies to acting in accordance with reason and virtue. This is where the concept of moral duty emerges, but the normative force must apply to all instances of kathêkonta. Visnjic suggests that we think of these as prescribed actions rather than merely appropriate ones (p. 21). Thus, it is prescribed by Nature that plants will bear fruit in season. This is much stronger than saying that it would be merely appropriate for them to do so. Visnjic also gives an interesting discussion of Zeno’s own etymology of the term, at pp. 22-9, which I pass over due to limitations of space in this review.
The second chapter argues that the Stoics did not see kathêkonta as rules for conduct. If one traditional view of Stoic ethics proposes rules but no duties, Visnjic argues for duties but no rules. Here he builds on previous work by Vander Waerdt, Inwood, and Vogt. The nearest we come to a universal rule in Stoic ethics is the broad commandment to be virtuous, but this is of little use in practical deliberation (pp. 36-7). So, how does a Stoic decide what to do? One of the criteria reported to us is the correct selection of indifferents, which will involve assessing their relative value. Another is making sure that one does not select indifferents at the expense of virtue. For the most part, Visnjic argues, duties are relative to situations. For example, usually one’s duty would be to respect one’s parents, but this is not a universal rule because in some circumstances it does not apply—if, for instance, they were engaged in unacceptable behaviour. Extreme circumstances can thus flip what would normally be a duty into a moral error, and vice versa (see the table on p. 57). Thus, there are no universal rules and on this issue the Stoics differ from Kant.
If there are no rules, then how does one decide what to do? This is the topic of the third chapter. Visnjic looks at evidence from Cicero’s De officiis, Seneca, Epictetus, and Marcus Aurelius, and argues that all these sources for Stoic ethics mention the same set of ideas that ought to guide one in moral deliberation. This Visnjic calls the formula. These ideas are: (i) humans are social beings with common interests; (ii) we are all parts of a single body, Nature; (iii) individual benefit aligns with collective benefit (pp. 67-8). There are no rules in Stoic ethics: what the correct thing to do must be worked out in each new situation; but these guiding principles enable one to choose what to do when faced with competing alternatives.
Having rejected rules but identified this formula, the fourth chapter aims to map out a method for deliberation. Visnjic outlines a four-stage procedure (pp. 78, 84-5, 98): (i) avoid rashness (i.e. only act according to reason); (ii) rule out courses of action that conflict with virtue; (iii) select indifferents on the basis of a calculation of relative value; (iv) avoid negligence (i.e. follow through and act). Alongside the formula, Visnjic also identifies a number of regulae (p. 80) that can be used to test the value of things. Epictetus regularly asks if something is “up to us” (eph’ hêmin) or the product of one’s prohairesis. If it is not, then it is clearly an indifferent and so not an end worth pursuing (e.g. public applause). Another mentioned by Cicero (that ultimately goes back to the Cynics) is that, if one thinks that an action ought to be concealed, then it is evidently not the right thing to do (pp. 82-3). Visnjic argues that these regulae act as initial filters and so come before the formula (p. 83). With reference to the four-stage procedure above, the regulae pertain to the second stage while the formula is to be used in the third stage.
A further element in Visnjic’s account is the contribution of roles, drawing on both Panaetius’s four personae and the account of roles in Epictetus. The roles that an agent occupies will be another contextual factor to take into account when deciding on an appropriate course of action. These include our own unique natures and characters. Thus, given who he was, it was entirely appropriate for Cato to commit suicide when he did, but for someone else it may not have been the right thing to do (pp. 92-3). If there are conflicts between the demands of different roles or personae, the formula can be used to help adjudicate. Visnjic also suggests that there is a deep connection between these two things: the fact that we are parts of a larger whole (as stated by the formula) is the reason why we have roles that are concerned with our relationships with other parts of the whole (p. 97). Visnjic sums up his account of Stoic ethics by saying that the Stoics developed a method of deliberation involving “a role-based framework” along with “key doctrines (the formula) and criteria (regulae)” that all work together in helping an agent determining their duty in any given situation (p. 100).
I found Visnjic’s account of Stoic ethics rich and stimulating. Although there are a number of minor points where I might disagree, on the larger issues I think he is broadly correct. I am now converted to the view that one ought to think of Stoic kathêkonta as duties rather than merely appropriate courses of action and I am grateful to Visnjic for pushing this point. I was already sympathetic to the “no rules interpretation” but it remained unclear precisely how deliberation would in practice take place, especially for a non-sage. Visnjic has helpfully laid out all the resources a Stoic might draw on to assist in that process.
Although that might sound like the end of the review, there are in fact two further chapters, primarily concerned with Kant. The fifth chapter examines Kant’s relationship with the Stoics. Visnjic suggests that few attempts have been made to examine this properly. I am not sure this is quite right. There have been a number of important studies already, many cited by Visnjic, and some that he does not mention. Visnjic claims that no one in Kant’s day could have adequately understood Stoic ethics, lacking as they did key works of scholarship such as von Arnim’s collection of fragments (p. 104). I think this seriously underestimates the sophistication of Stoic scholarship in the early modern period. Justus Lipsius’s two handbooks of Stoic philosophy published in 1604 give fairly comprehensive coverage of the doxographical material and were drawn on extensively by authors such as Leibniz and Bayle. Early eighteenth-century discussions by Buddeus and Brucker (which Kant knew; cf. p. 107) offer full and detailed accounts. The seventeenth and eighteenth centuries were, in many respects, a heyday for the study of Stoicism. Perhaps more importantly, though, it is not clear what this chapter adds to the overall discussion. What Kant did or did not know about the Stoics does not really bear on the central argument of the book, namely that Stoic kathêkonta ought to be understood as (Kantian-like) duties.
The sixth and final chapter pursues the relationship between Kant and the Stoics further. Visnjic highlights some important differences between the two while reflecting on ways in which Kant might have been influenced by Stoic ideas via his reading of Garve’s German translation of Cicero’s De officiis. One big difference is between Kant’s desire to universalize maxims and the Stoics’ resistance to inflexible rules. But Visnjic also notes a potential influence insofar as the Stoic formula that we saw earlier pre-empts Kant’s formulation of the categorical imperative (pp. 128-9). This leads to the claim that the Stoics may help us to understand Kant’s ethics, which may well be true, but that seems to be the reverse of the main goal of the book, namely to turn to Kant in order to help us grasp the role of duty in Stoic ethics. Visnjic goes on to suggest that many of the maxims in Kant’s Metaphysics of Morals align with Stoic ethics (p. 130), but these are not discussed in any detail or even listed. The final conclusion to this chapter argues that while Kant and the Stoics share much in common, the Stoic view is preferable insofar as it is more flexible, taking into account “differences of individual temperament, abilities, and social roles” in a way that Kant’s categorical imperative cannot (p. 133). There is much of interest in this chapter, although it is perhaps underdeveloped in places. But, as with the previous chapter, it is not entirely clear what it contributes to the central aim of the book. That Kant developed an account of duty while reading Cicero does not really offer support for the claim that the Stoics understood kathêkonta as duties. But fortunately this does not damage the overall project, for Visnjic has already—to my mind successfully—made a case for that in the earlier chapters.
 Inevitably I have to mention D. Doyle and J. Torralba, ‘Kant and Stoic Ethics’, in J. Sellars, ed., The Routledge Handbook of the Stoic Tradition (Abingdon: Routledge, 2016), 270-83, and their list of further references.