The philosophy and science of (Stoic) free will

Frontal lobes and hegemonikonTime to tackle again the debate that never goes away: how is the Stoic idea that we can work to improve our character, or — which is the same — Epictetus’ contention that some things are up to us and other things are not up to us, compatible with the (also Stoic) contention that we live in a universe determined by a universal web of cause and effect? In other words, how is Stoic “free will” going to square with their metaphysical position of physicalism? And, moreover, hasn’t modern neuroscience “demonstrated” that there is no such thing as free will?

Let me summarize the answers upfront, and then we’ll dig into the details, with the help both of scholarly work on Stoic philosophy and of scientific research on the human mind. In a nutshell: “free will” is an awfully confusing term that should never, ever, be used again. (Yes, I know, it’s in the title of this post. That’s because I wanted to grab your attention.) Instead, we should use the word “volition,” which — as we shall see in a moment — is both the best translation of what Epictetus means by the Greek term prohairesis as well as the appropriate technical term used by modern cognitive scientists. Moreover, the Stoics had a sophisticated causal model of volition (it may be good to re-read this post on Chrysippus’ metaphor of the rolling cylinder, before proceeding further), which turns out to be in very good agreement with the findings of modern science (yes, including the (in)famous Libet experiments popularly, but mistakenly, assumed to “demonstrated scientifically” that there is no such thing as free will; more on that below). Okay, let’s get started.

To begin with, the Stoics used two terms within the context of this discussion: hêgemonikon and prohairesis. The two are often treated as interchangeable, but Anthony Long, in his excellent Epictetus: A Stoic and Socratic Guide to Life (see my two commentaries here and here) draws an interesting and useful distinction between them.

Hêgemonikon is the most common Stoic term, and broadly speaking it is a faculty of the mind that has four “powers,” according to this helpful article in the Internet Encyclopedia of Philosophy: “presentation [phantasia], impulse [hormê], assent [sugkatathesis], and reason [logos].” The ancient Stoics thought that the hêgemonikon resided in the heart, a notion for which they were ridiculed by Galen, Marcus Aurelius’ personal doctor. Galen was right, of course, and I suggest that modern neuroanatomy locates the hêgemonikon in the frontal lobes.

The frontal lobes are areas of the brain that are particularly developed in both humans and other great apes (but, interestingly, not so in lesser apes and monkeys). The frontal lobes (one per hemisphere) are the largest of the four lobes of the mammalian brain, and experimental research has associated them with the following functions: reward, attention, short-term memory tasks, planning, and motivation. They also allow us to project the future consequences of our intended actions, to choose between what seem to us as good or bad actions, to override and suppress socially unacceptable responses, and to assess similarities and differences between things and events. That sounds to me very much like what the Stoics were talking about whenever they used the term hêgemonikon, usually translated as ruling faculty. Here is Marcus, for instance:

“Things stand outside of us, themselves by themselves, neither knowing anything of themselves nor expressing any judgment. What is it, then, that passes judgment on them? The ruling faculty.” (Meditations, IX.15)

Modern science tells us that the frontal lobes do not fully mature in human beings until our late ‘20s, and of course a variety of situations can impair their proper function, from accidents such as the famous one that occurred in 1848 to the American railroad construction foreman Phineas Gage to strokes, Alzheimer’s disease, and various forms of dementia.

Interestingly, according to Long:

“Hêmonikon does not mean rationality; it is a term that applies to the souls of animals who lack rationality as well as to human beings“ (p. 211)

Which is in broad agreement with the above mentioned scientific fact that all mammals have this structure, albeit in a less developed form than in the great apes. The Stoics were also clearly aware that there are conditions in which one’s hêmonikon is impaired, by age or disease, or not yet fully formed, in children.

Long insists, and it seems to me that he is correct, that there is a good reason why Epictetus — uniquely among the Stoics — switches to prohairesis, instead of hêmonikon. Prohairesis refers to a faculty that is unique to humans, and in a sense is a specific sub-component of the hêgemonikon:

“We should take prohairesis to refer to the human mind in just those capacities or dispositions that Epictetus constantly maintains to be completely ‘up to us’ and free from external constraint.” (p. 211)

What’s the difference? One of the characteristics of the hêgemonikon, as we have seen, is that it is presented with phantasia, or impressions, both external ones (from our sensory apparatus) and internal ones (from memory). Such presentation, according to Epictetus, is automatic, i.e., it is not “up to us.” The remaining three powers of the hêgemonikon, however, impulses, assent, and reason are up to us. So we can think of prohairesis as the ability to reason and to give or withdraw assent to our impressions — thereby controlling our impulses — that is part of the hêgemonikon. I will leave it to neuroscientists to work out exactly which structures within the frontal lobes are more concerned with reasoning and decision making, and which are devoted to sensorial inputs and memory. The answers are empirical in nature, but do not affect the philosophy at all.

[Incidentally, as Long points out, Epictetus is not alone here: Aristotle also adopted the term prohairesis to mean “the deliberated desire of things that are up to us.” Moreover, Aristotle too judges what he calls “prohairetic disposition” to be a better assessment of moral character than action, presumably because actions are not entirely up to us, only judgments are. (p. 212)]

We are now in a better position to make sense of one of the most famous passages in the Discourses:

“For a start, don’t be carried away by [the impression’s] vividness, but say: Wait for me a bit, impression; let me take a look at you and what you are about, let me test you. Next, don’t let it lead you on by painting a picture of what comes next. Otherwise, it is off and away, taking you wherever it wishes. Instead, confront it with another impression, a fine and noble impression, and dismiss this foul one.” (II.18)

It is the hêgemonikon that both presents us with the impression (say, of an attractive member of the other sex) and with memories to draw from (of pleasurable previous sexual encounters). But it is our prohairesis that applies reason to the situation and denies assent to the impression (I am in a committed relationship, and I will therefore not pursue sex with another person on the side).

That also makes sense of why the Stoics, and Epictetus in particular, insisted that the only things that are truly good or bad are our judgments: the impression itself is neutral, because it is a fact about the world, and moreover is not under our control. It is us, through the faculty of prohairesis, who attach a value judgment to things and events. That attaching of a judgment is under our control, and so the only truly good thing is to have a well functioning prohairesis, and the only truly bad thing is to have a malfunctioning one (which leads to the condition often describe as amathia, or un-wisdom).

Long provides his readers with a very good discussion of why he ends up translating prohairesis with “volition,” and it is well worth attending to his reasoning. He considers three other options: moral purpose (or moral character), will, and agency. He discards the first possibility, because prohairesis can be good or bad, while “moral” has a positive meaning only; moreover, the word is tainted by later connotations that would distract and lead us to misunderstand the Stoic meaning.

What about will? He has actually translated prohairesis that way, occasionally, particularly because Epictetus does use phrases like “if you will, you are free.” But, again, the term has become loaded with especially Christian-influenced meaning, and — more importantly — it may lead us to erroneously conclude that Epictetus is thinking of a faculty of the will distinct from assent and impulse, which he is definitely not.

Agency, says Long, is a better alternative, and indeed it is the one used by modern Stoic Lawrence Becker throughout his A New Stoicism, about which I have recently published a ten-part commentary. But Long isn’t happy with agency either. Consider this passage:

“And who told you; it is your function to walk unimpeded? What I was telling you is that the only unimpeded thing is the impulse. Wherever there is a need for the body and the body’s cooperation, you have long ago heard that nothing is your own.” (Discourses IV.1.72-73)

What Epictetus is reminding his student of, here, is that even our bodily actions are not entirely up to us: we may decide to start walking, but we could be paralyzed by disease, or chained to a wall by a tyrant. So the action is not (entirely) up to us, only the impulse to perform the action. Since “agency” typically carries a meaning of actually doing things, not just willing them, then I would have to agree with Long’s take.

Hence the final preference for volition, which in modern psychology is “the cognitive process by which an individual decides on and commits to a particular course of action. It is defined as purposive striving and is one of the primary human psychological functions.”

As Long correctly points out, volition is not contradictory to a physicalist view of the world as determined by cause and effect:

“We take people to have volitions irrespective of whether these are predetermined or independent of antecedent causation.” (p. 220)

And, moreover, modern psychological science considers volition to be “a process of conscious action control which becomes automatized” (see link just above). But wait a minute! Isn’t it a fact of modern science that free will, however one wishes to call it, is an “illusion”? Specifically, didn’t the famous experiments by Benjamin Libet back in the 1980s conclusively show that to be the case? Does that not mean, therefore, that the entire Stoic philosophy of mind, and hence the crucial idea of the dichotomy of control as expressed by Epictetus at the very beginning of the Enchiridion, crumble under the pounding of modern science? Nope, not at all. On the contrary, Libet’s experiments, and subsequent others carried out since, spectacularly confirm the ancient Stoic intuition about prohairesis.

Libet performed some fascinating experiments on conscious vs unconscious decision making, beginning back in 1983. Briefly, he asked subjects to follow the movements of a dot on the screen of an oscilloscope. The dot moved like the hands of a clock, but faster. Libet told his subjects to move a finger at a moment of their choice during the experiment, noting the position of the dot when they became aware of their decision to act. The experiment showed that the decision to move the finger entered conscious awareness about 200 milliseconds before the actual movement. But, stunningly, there was a rise in the so-called “readiness potential,” which is thought to be associated with the preparation for action, about 550 milliseconds before movement. So the subjects appeared to get ready to move the finger a full 350 milliseconds before they became conscious of their decision to do so. (Indeed, in later experiments, the readiness potential has been shown to build up even as long as 1.5 seconds before movement.)

Taken at face value, Libet’s results seem to show that we decide our actions unconsciously, and that what we call consciousness is simply a (late) awareness of a decision that has been made. There are several well known criticisms of such conclusion, beginning with the obvious one, that the experimental conditions have precious little to do with the recursive, complex behavior that we normally label “conscious decision making,” and which is understood as a continuous feedback loop between what Daniel Kahneman calls System I (fast, subconscious) and System II (slow, deliberate) brain processing systems.

But in fact it was Libet himself who rejected the facile “free will is an illusion” interpretation of his own research. Here is part of his commentary:

“The finding that the volitional process is initiated unconsciously leads to the question: is there then any role for conscious will in the performance of a voluntary act? The conscious will does appear 150 msec before the motor act, even though it follows the onset of the cerebral action by at least 400 msec. That allows it, potentially, to affect or control the final outcome of the volitional process. An interval msec before a muscle is activated is the time for the primary motor cortex to activate the spinal motor nerve cells, and through them, the muscles. During this final 50 msec, the act goes to completion with no possibility of its being stopped by the rest of the cerebral cortex. The conscious will could decide to allow the volitional process to go to completion, resulting in the motor act itself. Or, the conscious will could block or ‘veto’ the process, so that no motor act occurs.” (B. Libet, Mind Time: The Temporal Factor in Consciousness, 2004, p. 137)

Note that the motor cortex in question is part, surprise surprise!, of the frontal lobes (specifically, part of the posterior border of the lobe, called the precentral gyrus), which I have suggested is the anatomical counterpart of both the hêgemonikon and enables the faculty of prohairesis.

Also, more recent research (summarized here), has led to a re-interpretation of Libet’s original findings that aligns them even more with the intuitions of the Stoics. For instance, a group of researchers in Germany has modified the original protocol to test Libet’s idea of a veto power exercised by conscious thought. Bear with me for a minute, because some of the details are important.

Subjects were asked to hit a foot pedal as quickly as possible after seeing a green light on a screen, but also to stop themselves from doing so (i.e., cancel their own movements) whenever a red light appeared. Researchers then put the red light under the control of a computer monitoring the participants’ brain waves. The twist was that whenever the computer detected the above mentioned readiness potential building up it would make a red light appear. In agreement with Libet’s veto hypothesis, participants were, in fact, able to stop themselves from pushing the pedal, reversing the build up of the action potential. This was possible up until a point of no return: if the red light was too close after the green one (about 0.25 seconds) then the foot movement could not be completely inhibited.

And there is more. A French team of neuroscientists published a paper in 2012 in the prestigious Proceedings of the National Academy of Sciences in which they argued for a different interpretation of Libet’s original experiments. They suggest that the readiness potential does not, in fact, signal the brain’s preparation for a specific action. Rather, the potential goes up and down randomly, but movement can only occur when a certain threshold in the potential is reached. Sure enough, they conducted an experiment in which they asked subjects to press a button, either at moments of their own choosing, or when they heard a random click. The results show that the response to the random clicks were much faster when they happened to coincide with a (again, random) surge in the readiness potential then when the potential happened to be low. So the potential is not really a sign of an already made unconscious decision, but rather one of a number of co-occurring causes that facilitate the movement.

All of the above seems to me eminently compatible with the Stoic take on volition. Please understand that I am not suggesting that the ancient Stoics somehow anticipated modern neuroscience. That would be preposterous. They knew nothing about action potentials, and they even got spectacularly wrong the anatomical location of the hêgemonikon. But their intuitive understanding of human psychology — on which they built their moral philosophy of action — was right on target, which makes their philosophy perfectly compatible with modern cognitive science. (For another example of such compatibility, this one concerning the Stoic treatment of emotions as cognitively informed, see here.) There is no magic here, the Stoics were simply astute observes of human nature.

To summarize then: the hêgemonikon, our ruling faculty, is roughly equivalent to the functions performed by the mammalian frontal lobes, which are particularly developed in the great apes, and that in the human species reach full maturity in our late ‘20s. Prohairesis is our special faculty of deliberate, rational judgment, and is made possible by sub-components of the frontal lobes. Our volition is compatible with the fact that the cosmos is characterized by a universal web of cause and effect, because some of these causes are internally generated (see Chrysippus’ cylinder), which makes Stoic philosophy of mind a type of compatibilism about “free will” (and please, let’s no longer use that term!). Finally, not only there is no contradiction between modern cognitive science and the Stoic idea that some things (namely, our judgments) are “up to us.” It is, on the contrary, the case that modern science tells us about the anatomical bases and physiological mechanisms underlying prohairesis. It is this congruence between early Stoic intuitions about human psychology and nature and modern science that make their philosophy still so useful today. We can, therefore, agree with Epictetus when he says:

“You are not flesh or hair but volition; if you keep that beautiful, then you will be beautiful.” (Discourses III.1.40)


12 thoughts on “The philosophy and science of (Stoic) free will

  1. Ricardo Nassif

    “Also, more recent research (summarized here), has led to a re-interpretation of Libet’s”[…] – Was it meant to be link (summarized here)? Or, maybe, just a reference to the two paragraphs that followed.


  2. Steve Olson

    Please let me know if you think I have this correct:
    At any decision point in time, when I am presented with certain impressions that trigger my desires to pursue a course of action, the assent to action will be determined by whatever reasoning powers I possess and the importance and intensity of my particular desires at that time. In that sense, I can only do what this particular calculus of external and internal stimuli and reasoning process allows me to do and “I could do no other”.
    However, over time by being exposed to the proper coherent philosophy to redesign the hierarchy of my desires and by training my reasoning faculty to improve my decision making software, I will have the options and ability to change the trajectory of my particular cause-effect chain.

    Liked by 1 person

  3. jbonnicerenoreg

    I think the reason the Stoics got it right has to do with the distinction of the “manifest image” and the “scientific image”. The Stoics, as you said, were keen observers of human nature or the phenomenon of consciousness, the manifest image. And since the scientific image must ultimately make sense in terms of the manifest image (what else could observation, confirmation or falsification mean in Science) since the science is trying to explain the observations. Oddly enough, Sellars said the opposite!

    Liked by 1 person

  4. Massimo Post author


    I tend to agree, but I’m not sure that’s what Sellars said. He did sat that in case of conflicts between the two images the scientific one “wins,” so to speak. For instance, if the manifest image tells us that the Sun “rises,” but the scientific one tells us that it is actually the Earth that rotates, we have to go with the second one.

    But he also said that things like reasons and jusdgments and values don’t really figure in the scientific image, so that we need the manifest one to guide our lives.

    A Good Stoic would take the same approach: by all means, let us update our view of the world according to what the best science says, but let’s not fall into the scientistic trap that what science says is the only thing that is worth saying.


  5. Patrice Ayme

    Dear Massimo, thanks for this very interesting essay. I was unaware of the most recent experiments on volition, post-Libet.
    You wrote: “this was possible up until a point of no return: if the red light was too close after the green one (about 0.25 seconds) then the foot movement could not be completely inhibited.” Shouldn’t not it be if the red light was less than 0.2 second before the onset of motion?

    “Free will” or more exactly, volition, is not free: it is a prisoner of our own brain, its neural networks, its experiences, associations, theories and emotions. All those, in turn, were built progressively, over years and even decades, nonlinearly feeding on themselves, and back to the environment they evolved from and modified in turn (in that environment, typically, one’s family). Volition is a house we helped built, and also a robot we inhabit.

    This fits with the rolling cylinder metaphor: some impulse, say a sensation gets something to roll (or not) according to its nature, inertia does the rest (the Greco-Romans didn’t have inertia as an explicit concept, they touched it there in an important example which Galileo Galilei would run away with, establishing deep laws thanks to experiences involving cylinders). This distinction between impulse and subsequent evolution, is actually fundamental to differential equation theory: the initial conditions are a different input from the structure of the equation itself. Different initial conditions can give completely different results, from the same differential equation.

    The nidopallium in birds is involved in executive functions, and higher cognitive functions. One intricate behavioural process governed by the nidopallium in birds is migration. There is significant neuronal recruitment to this region of the avian brain during migratory flight. It enhances cognitive potency in the nidopallium.

    Thus birds benefit from improved navigational capabilities during migration, prompted by the significant changes in spatial sensory stimuli. This illustrates that neuroplasticity in the brain, avian, or not, depends upon the mission. We build the cylinder we are going to roll, depending upon what we do, and, or, plan to be doing. But, once it’s mostly built, our existing neural networks, and the neurohormonal machinery bathing them, presenting enormous inertia, is how volition rolls.


  6. Nanocyborgasm

    An amusing etymology is found in hēgemonikon in that it literally means “leading” but in the sense of leading from the front, because it’s from the verb hegeisthai (lead the way) as opposed to the more generic verb for leading agein. That’s relevant because the hēgemonikon is supposed to be at the forefront of one’s decisions, not emotions. And it so happens that it’s in the frontal lobe. Ha!


  7. jbonnicerenoreg

    Massimo, In the case of the “sun rises” we go with the scientific image provided that the science explains why it looks like the sun is rising. Physics says the table is 99% space. Why does it feel solid? I think this is fairly uniform across science when the the science has consequences not on accord with the manifest image.


  8. Massimo Post author


    Well in those cases we know that there is a gap between the two images. But I’m not about to reject quantum mechanics because I don’t get how light can be both a particle and a wave.

    Liked by 1 person

  9. Roberto Sans

    Dear Massimo

    Thank you for this excellent article which makes a quite thorny subject much more clear in my mind. I think that you are absolutely right in your understanding of the meaning of the readiness potential. The analogy with the cylinder of Chryssipus seems quite good to me as well. Have you thought of developing these ideas into a full book? I believe that it would be quite a complex but relevant subject .


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