There is a familiar tension within Stoicism between determinism and moral responsibility. The Stoic response is typically to restrict each portion of the puzzle to different realms. Not all Stoics agree on how this division should be maintained. The ancient Stoics maintained that there is one world governed by two principles: matter and reason. Modern Stoics divide the world into two along those same lines. In the world of matter, action is determined. In the world of reason, it is deliberated and chosen. I shall be concerned here with how the modern Stoic understands each individually and how they relate. The Stoic cannot ultimately resolve this tension.
The Stoic account of the world of matter is straightforward. It is ordered by the categories, which permit the theoretical understanding of material events by situating each within a causal series. And so it is with human action, embodied as it is. But in the world of matter, human action is not caused by some intention or will. As the Stoic makes clear, the will is a practical postulate which does not bear on the theoretical understanding of the world of matter: “the postulates play no theoretical or explanatory role whatsoever. They provide us with concepts that define the intelligible world, but we have no intuitions to which we may apply those concepts, and consequently no theoretical knowledge of their objects.” Moral responsibility has its source therefore in the world of reason, the intelligible world, not the material. This is where the real meat of the Stoic account lies.
For the Stoic, the world of reason is revealed in a particular standpoint, one in which action is deliberated. As they say, “In order to do anything, you must simply ignore the fact that you are programmed, and decide what to do—just as if you were free . . . It follows from this feature that we must regard our decisions as springing ultimately from principles that we have chosen, and justifiable by those principles. We must regard ourselves as having free will.” The world of reason, on this view, is populated by those practical postulates needed to completely determine deliberation and moral action. Most important of these for my purpose is the will. This is what deliberates and ultimately chooses some course of action. It is “a rational causality that is effective without being determined by an alien cause.” The will is self-determining, and so is subject to no cause. It follows that moral action qua moral is undetermined by any element of the phenomenal world. It is entirely bound within the intelligible.
The Stoic takes this to ground the freedom of the will. But this is not to say that the will is undetermined. For the Stoic, the will is free only insofar as it is causally isolated from the world of matter. It is nevertheless bound to law because it is itself a causality. This follows immediately from the Stoics’ nomological account of causation: “Since the concept of a causality entails that of laws . . . it follows that freedom is by no means lawless.” Of course, the account of causation that applies here is relevantly distinct from that of the world of matter. The will is not bound to antecedent cause, but its deliberation is nevertheless constrained in the same sort of way. The law still applies to the will, but here the law is rational, not material: “The free will therefore must have its own law . . . [S]ince the will is practical reason, it cannot be conceived as acting and choosing for no reason. Since reasons are derived from principles, the free will must have its own principle.”
The laws which govern the will have their source in the reasons that a will has for choosing one course of action over another. These reasons begin with incentives. For the Stoic, “An incentive is something that makes an action interesting to you, that makes it a live option . . . [It does] not yet provide reasons for the spontaneous will, [but] determine[s] what the options are—which things, so to speak, are candidates for reasons.” Incentives become reasons once they are adopted as maxims. But since incentives don’t just disappear, this process of adopting an incentive as a maxim rather consists in the rational ordering of our incentives, of choosing which incentives take precedence over others.
For the Stoic, the rational order of incentives is readily given in reason as revealed by the structure of the will. Because the will is itself uncaused, it is spontaneous. But in order to be a cause, it must adopt some maxim. As the Stoic puts it, “At the standpoint of spontaneity, the will must . . . choose a principle or a law for itself. Nothing provides any content for that law. All that it has to be is a law.” This content must be compatible with the spontaneity of the will and must be available in the world of reason. For the Stoic, there is only one thing which meets these criteria: the will itself. And so the will may ultimately take itself as its content. The Stoic represents this by the following principle: “act only in accordance with that maxim through which you can at the same time will that it become a universal law.” They call this the Formula of Universal Law, which they say “merely tells us to choose a law. Its only constraint on our choice is that it have the form of a law. Nothing provides any content for that law. All that it has to be is a law.” It is of course plain that the Formula of Universal Law does not merely tell us to choose a law. It tells us to choose a universal law. There is a problem here which I shall come to later. For now, I must continue with the Stoic account of moral responsibility.
By now in their account, the Stoic maintains that their account of right action has been satisfactorily demonstrated. What remains is to account for how human beings may act rightly. This is in effect to account for how the world of matter and the world of reason interact. The ancient Stoic can easily account for this because they hold that there is only one world which can be explained in two distinct but consistent ways. The modern Stoic might seem to face a deeper difficulty. However, their account is ultimately the same. The difference here is that they have inverted the metaphysics of their ancient predecessors. Where they ancient Stoics took matter to be fundamental, the modern Stoic holds that the world of matter has its ultimate source in the world of reason, which they then call the noumenal world. As such, when a human being wills some action, its influence in the world of reason makes it so also in the world of matter.
The will does not have sole influence over the world of reason, however. The world of reason is divinely ordered, and so one’s will must contribute to this order in some way. How this occurs is unclear in the Stoic literature. Whatever happens, the parallel limitation occurs also in the world of matter as represented by the laws of cause and effect. The human will, as realised by the material body, is bound by these laws and therefore not completely free. It is always bound by what appears to it as a possible course of action: if that is one is not met by the appropriate kinds of intuitions that permit right action in a given situation, one cannot possibly act rightly. This is of course not a strictly passive process, but it has important passive elements: even if we purposely look for ways to alleviate suffering, for example, these ways may never appear to us even if they are in plain view. It follows from this that in the world of matter the human is not perfectly rational, even if the isolated will in the world of reason is. And so this imperfect rationality is the source of moral responsibility: we are capable of acting on the moral law and yet sometimes, through our own faults, fail to perfectly realise it in the world of matter.
Just as it was for the ancient Stoics, becoming moral for the modern is therefore a process of more completely realising the moral law in the world of matter. This is the importance of virtue. The virtuous person takes the moral law, as given in reason, to be their end. And virtue must be cultivated. As it was for the ancient Stoics, so it will be for the modern: in becoming virtuous, one meditates upon one’s incentives and subordinates those of the inclinations while elevating those of reason. This is not an easy process, as the Stoic says, for “you are imposing a change on your sensible nature, and your sensible nature may, and probably will, be recalcitrant. Although adopting an end is a volitional act, it is one that you can only do gradually and perhaps incompletely.”
It does not matter how great this imposition is: we are obliged to make it from our nature as agents, as rational creatures yearning to be free. But for the Stoic, freedom is only given in subjugation to the moral law. Man is not born free: he becomes free by learning to bear the weight of his chains. Only as a slave within the Empire of Ends shall one have liberty. And so our obligation, as reason commands, is to board the Clotilda and set sail for the Land of the Free. The Stoic wishes to defend this bald incoherence. I will not allow this. The injustice of this empire is already apparent. Let me bring it more clearly into view.
The Stoic is often quite careless with their concepts. Consider the problem that I have already mentioned, for example. The spontaneity of the will on their view demands some law, but it does not demand some universal law. The confusion here consists in what the Stoic takes laws to be and what they constrain. They think that to choose some maxim for oneself in the world of reason is also to choose for all others. Since each will is equal under the laws of reason, to make oneself an exception would be irrational. But this is not quite right. There is a relevant difference between my will and yours: I make decisions for myself and not for you. The universal law here applies only to all those things which are me. Yet this gives absolutely no content to the will, and so the recursion here contributes nothing to what one might be able to take as a maxim.
This is not to say that the will cannot in principle adopt the Formula of Universal Law as its maxim. It is only to say that so adopting it does not preserve the spontaneous condition of the will. In order to take it as a maxim, one must bind oneself to the law of the cosmopolis, the Empire of Ends, the Formula of Humanity, which indeed cannot be given purely in reason. It is of course unclear whence this law can be given at all except through some mystical communion with God, but let’s set this aside for now.
It is more important that in clearing up the Stoics’ concepts, we recognise now that the moral maxim is on roughly equal ground as the maxim of self-love. The former says that “I will do my duty and what I desire only if it does not interfere with my duty.” The latter says that “I will do what I desire and what is my duty only if it does not interfere with what I desire.” Both destroy the spontaneity of the will to some degree, though the Stoic will still insist that the former is preferable because the latter destroys spontaneity in a particular way: “Incentives of inclination cannot move the will to abandon its position of spontaneity, since they cannot move the will at all until it has already abandoned that position by resolving to be moved by them.” The moral maxim, they claim, does not do this since it remains open ended what sorts of actions may fulfill one’s duty. On closer inspection, however, there is no asymmetry here. In both cases, the will must first resolve to be moved before it can be, and in both cases there is any number of actions which might satisfy a maxim. To be a slave of one’s passions is essentially the same as being a slave to the law.
But this is quite a minor problem, one that merely follows the trail which much deeper confusions have set out for the Stoic. Plutarch’s criticism of the ancient Stoics has not been addressed by the modern, for example. The modern Stoics attempt to hold both that a will is always moved by an incentive (eventually) and that it cannot be moved by it until it resolves to be moved. The latter for the Stoic requires assent, or what they more commonly call judgement. Plutarch rightly points out this inconsistency and maintains that judgement is not only not required for action but also possibly harmful to right action. Judgement changes the ways in which both the world is perceived and one’s agency is constituted. Acting without judgement does not do this: it allows one to take an open-ended approach to the world and to oneself in order to seek what is truly good and act for its sake.
One reason that the Stoics deny this is their nomological account of causation. In order to be moved by some incentive, they think, one must be able to comprehend the law that addresses this incentive. These laws are not given in intuition, but rather by abstraction in reason. And so to act on any incentive is ultimately to make a judgement about some law and one’s own relation to it. Hence there is no way around positing laws or reasons to which the will is in some sense bound. And yet, there are no such laws. In recognition of an incentive, the will constructs a model which guides its response. But in no case need this model be expressed as true or even as nomological and making a judgement one way or the other serves only to constrict the will and diminish its openness to what must be done.
The Stoic takes this to be unnecessary because they conceive of the will as ultimately uncaused and completely spontaneous: in other words as free. But they have no grounds for this assumption. For the Stoic, this is a practical postulate necessary in the moment of deliberation and decision. As one reflects on one’s choices, that is, it is not relevant that one’s actions are already determined since subjectively one must nevertheless decide what must be done. And since the will is not (relevantly) determined, they say, it must be free. This does not follow. There is only one thing that is relevantly true here: that in deliberation, it is subjectively opaque what one has already been determined to do, if anything. There is an epistemic distance here that cannot be traversed. The Stoic attempts to infer from this distance the existence of the will and a whole world that it populates. So dogmatic they are that other more reasonable inferences fail to cross their mind at all. Whatever might be true metaphysically, the determination of one’s actions by prior events is simply irrelevant to whether one is morally responsible for a given act. Yet the Stoic is bound to their metaphysical inferences as if these are given in reason alone and not by some pretheoretical psychological disposition which blinds the Stoic to other available options.
And this is really the danger of Stoicism: so blinded they are by their commitment to empire that they bend the world to abide by its edicts. Up is down, war is peace, intuition is reason, and slavery is freedom. Let this not be so: let us go forth and establish our liberty, our freedom from the edicts of the Empire of Ends. And where the Stoic attempts to enslave us, let us cast his reason into the flames. Perhaps when he sees it transformed into ash he will realise at long last that his empire is not eternal.
 There are of course two kinds of modern Stoic. One kind is mere atavism and hence does not differ at all from ancient Stoicism but for a lack of detail and rigorous argument. This is the sort of foolish nonsense which Massimo Pigliucci among others promotes and hence may be easily dismissed. But another kind is adaptation. These Stoics have reinvented themselves for a different age. They cannot be similarly dismissed and must be directly opposed, for they too bear the same faults as their predecessors despite their differences. They too would see us subjugated to empire. They too would see us enslaved.
 Christine Korsgaard, “Morality as Freedom,” in her Creating the Kingdom of Ends, Cambridge: Cambridge University Press, 1996: 172-173
 Ibidem, 163
 Immanuel Kant, Groundwork for the Metaphysics of Morals, 446, quoted in Korsgaard, “Morality as Freedom,” 163
 Korsgaard, “Morality as Freedom,” 163
 Ibidem, 165
 Ibidem, 166; italics in original.
 Kant, Groundwork, 4:421
 Korsgaard, “Morality as Freedom,” 166
 Ibidem, 180
 Ibidem, 166