From ancient to new Stoicism: I—Stoic physics

A conceptual map of where Stoicism came from and where it may be going

Chrysippus of Soli (center), surrounded by his famous cylinder and cone (see text). Trajan’s Market Museum, Rome. Photo by the Author.

Time to update Stoicism for the 21st century and beyond, don’t you think? I mean, the philosophy has been around since the 4th century BCE, but a few things have changed since then. Indeed, the initiative I recently announced, the School for a New Stoicism, has as its main objective to help bring this venerable and eminently practical philosophy squarely into modern times.

Naturally, I’m not the first one to try to update Stoicism, or to feel the need for it. In my mind the most serious attempt in that direction was made by Larry Becker, author of the aptly titled A New Stoicism. I made my own little contribution to the project by publishing an updated version of Epictetus’s Enchiridion entitled A Field Guide to a Happy Life.

This sort of efforts are different from those aimed at popularizing Stoicism, such as books by Don Robertson, John Sellars, and others. Though sometimes we see a combination of the two aims, as in Robertson’s Stoicism and the Art of Happiness, or Bill Irvine’s A Guide to the Good Life.

In this series of essays I want to do three things: first, to provide an accessible summary of the basic ideas that define Stoicism, because if we don’t have clarity about the starting point then we don’t know where we are going. Second, to discuss three major attempts made so far to update Stoicism to modern times. Lastly, to articulate at least a draft of my own thinking about what a 21st century version of Stoicism may look like.

Specifically, the plan is for the current essay to cover ancient Stoic physics; for the next two to complete the trio of Stoic fields of inquiry by discussing ancient Stoic logic and ethics respectively. We will then move on to consider Becker’s new Stoicism (essay four in the series), Piotr Stankiewicz’s “reformed” Stoicism (essay five), and Steven Gambardella’s new Stoicism (essay six). The final essay in the series will then get to my own proposal. How does that sound?

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My discussion of ancient Stoic physics, logic, and ethics is going to be based on my own understanding of the subject matter, developed over the past decade or so. However, an excellent scholarly source in order to dig deeper is the Stanford Encyclopedia of Philosophy’s article authored by Marion Durand and Simon Shogry. The bibliography section by itself is worth the effort.

Stoicism, founded by Zeno of Citium in Athens around 300 BCE, is a philosophical system comprising three pillars: physics, logic, and ethics. “Physics” comes from the Greek phusis, meaning nature. Physics, therefore, here stands for the study of nature, which includes what we would today call science and metaphysics. “Logic” included not just formal logic, but also epistemology, philosophy of language, and philosophy of mind. And “ethics” was far more encompassing than discussions about right and wrong action, including everything to do with human character and social-political behavior.

The basic idea put forth by the Stoics is that to live well (ethics) is possible only if one understands the world one lives in (physics) and reasons correctly about it (logic). Which strikes me as eminently, well, logical!

I’m starting this series with physics because that’s the way Durand and Shogry do it, but we could have just as well started with logic. Ethics, by contrast, has to go last, because it depends on the first two.

Please keep in mind that the objective of the first three essays in this series is to present a complete picture of ancient Stoicism, not (yet) to update it. So while I will be occasionally making comparisons with modern science, logic, and ethics, such comparisons are only meant to clarify what the ancients were thinking, not (yet) to suggest ways in which their notions might be updated and reinterpreted.

Stoic ontology: the nature of reality

The Stoics made a distinction between things that are real and things that exist, which is a bit puzzling from a modern perspective. But here is what they meant: the only things that actually exist, that are characterized by being, are corporeal, that is, made of stuff. You and me, and every other body in the universe are corporeal, and therefore exist. In fact, the category of being includes everything that is capable of interacting causally with other existing things. Causality, therefore, is the hallmark of existence: if something exists then it has causal powers; if something has causal powers, then it exists (and it’s made of stuff).

One immediate and major consequence of this way of viewing things is that the soul must be made of matter, because it has causal powers. The Stoics, therefore, rejected the notion of an incorporeal and immortal soul, which we find in both Plato and the Christians. The soul acts on bodies, and therefore it must itself be a body. If so, it decays and dies just like everything else. The theological implications are staggering…

However, the Stoics also recognized that a certain number of things don’t fall into the category of being and yet are part of reality broadly construed: time and place are two examples, and so are what they referred to as “sayables,” that is, the kind of things that can be expressed by language, including the content of our thoughts. Thoughts and concepts do not exist in the sense of being made of stuff, and yet they are part of reality. They are said to “subsist.” Graphically, this is what the whole shebang looks like:

The structure of reality according to the ancient Stoics: some things exist and others subsist. The first category includes things made of stuff and characterized by causal powers; the second category includes abstract thoughts that are not made of stuff and have no causal powers.

This, if you think about it, is very clever: it makes it possible for the Stoics to be materialists and to believe in universal cause and effect, while at the same time accounting for abstract concepts. It’s hard to find a better way to explain the structure of the world until we get to modern physics and philosophy, and even then the Stoics can very much hold their own.

The two cosmic principles

The ancient Stoics thought that the world comes together as a result of two principles: active and passive. The passive principle is what makes possible the existence of primary, inert, matter. The active principle, identified with God / Zeus, is what transforms inert matter into everything we actually see in the world: mountains, plants, animals, people.

This may sound like a dualistic view of the world, with two distinct principles interacting to yield the observable universe, but the Stoics very clearly insisted that the two principles are completely and thoroughly blended, so that they can be separated only for the purposes of discussion. The Stoics system of reality is therefore monistic.

One more important point about the two principles: the way in which the divine principle acts on inert matter is through something called pneuma (breath). This comes in different gradations, and the gradations are what makes possible the existence of different kinds of things: the lowest level of pneuma characterizes inanimate objects; a higher level is typical of plants; a still higher level of animals; and the highest level of them all, the logos, distinguishes humans and god itself.

If you think this sounds crazy or hopelessly old fashioned, please consider that modern string theory claims that the world is made of one type of things: vibrating strings. The frequency of vibration of each string makes it take on the properties of what we call particles, and these in turn make up the macroscopic bodies we see and interact with. I’m just saying…

Eternal recurrence and the living god

Stoic cosmology says that the universe began with a fiery explosion and that it will end with another fiery explosion. Only to start over again in a perpetual cycle of existence during which everything repeats itself in exactly the same way.

This may, again, strike us as more than a bit odd, until we realize that even modern cosmologists have contemplated the possibility of a cyclical universe, though I understand that the idea is currently a minoritarian one.

The reason each cycle would be identical, according to the Stoics, is because god doesn’t change its mind, it always does things in the best way possible. Modern cosmologists, by contrast, would say that each cycle would be different because it begins with a quantum singularity, which is a fundamentally random event that provides slightly different initial conditions every time it occurs.

Speaking of God: it exists (rather than just subsisting), because it has causal powers. It is also, therefore, made of matter. God is immanent throughout the universe and directs its development (providence). Moreover, god / cosmos is a living organism endowed with universal reason (logos). In an important sense, we are bits and pieces of the cosmic organism, and accordingly share in the logos.

There are often discussions about whether the Stoics were pantheists or panentheists, even among scholars. Pantheism is the notion that the divinity is identical with the cosmos; panentheism is the idea that the divinity is present everywhere in the cosmos but also extends beyond time and space. It seems to me that, according to these definitions, the Stoics were pantheistic, not panentheistic. But as I said, there is disagreement here, and ultimately it doesn’t really matter.

(Also, the two terms may simply not fit ancient thought very well: pantheism was coined by the mathematician Joseph Raphson in 1697, while panentheism was coined by the philosopher Karl Krause in 1828.)

Causality and determinism

We have already seen that the Stoics accepted universal causality, indeed they put into the category of being / existence only things with causal powers.

Their conception of causality is deterministic: everything that happens, everywhere and at all times, is the effect of antecedent causes, no exceptions, no miracles. This, obviously, has implications for things like moral responsibility, which the Stoics nevertheless wished to preserve.

They did this by adopting a position that modern philosophers call “compatibilism” about free will (the latter being a term that did not exist in philosophical discourse at the time, and which is instead linked to Christianity and the problem of evil). The best known articulation of their thinking on this matter concerns Chrysippus’s famous example of the cylinder and the cone:

“[Chrysippus] resorts to his cylinder and cone: these cannot begin to move without a push; but once that has happened, he holds that it is thereafter through their own nature that the cylinder rolls and the cone spins. ‘Hence,’ he says, ‘just as the person who pushed the cylinder gave it its beginning of motion but not its capacity for rolling, likewise, although the impression encountered will print and, as it were, emblazon its appearance on the mind, assent will be in our power.’” (Cicero, De Fato, 43)

The idea is that the cylinder and the cone are both being pushed from the outside, that is, they are subject to the same external force. Yet, they respond differently—one rolls, the other spins—because of the differences in their internal natures.

Analogously, human beings react both to external and internal causes, and when we say that something is “up to us” (as Epictetus puts it) we mean that it is rooted in internal causality. Modern critics of free will miss the point when they present human beings as marionettes whose threads are moved by external events. We are more like sophisticated decision-making machines capable of reacting to external inputs by way of appropriate, internally generated outputs. In fact, unlike the cylinder and the cone, we are capable of altering our own internal nature, i.e., our character, by willfully working on it through a series of continuous feedback loops. Marvelous!

The Stoics also had a response to another then popular problem meant to undermine their determinism, the so-called lazy argument. The idea was that if I fall sick and it is fated that I will recover, why bother calling the doctor and taking the medicines? Chrysippus responded that my recovery is co-fated, that is, it’s the result of a number of concurrent causes, including the fact that I do call the doctor and take the meds!

Psychology

Although we don’t usually think of psychology as a hard science, and certainly not as part of physics, the Stoics included the study of the human mind in their broad understanding of nature, which makes perfect sense to me.

The basic idea was that the soul—which, remember, is corporeal—is permeated by a high level of pneuma, which makes it possible for us and for other animals (but not for plants and inert matter) to perceive things. Such perceptions are the raw material for what the Stoics called “impressions,” i.e., basic, automatic judgments about the world. Depending on how we are hit by a given impression we (and other animals) then experience an “impulse” or movement to act in a certain way. (This does not mean that we act impulsively, “impulse” is a technical term in Stoic psychology.)

For instance, my dog received the impression that I’m approaching him while holding a leash and he has the impulse to get up from the couch and get ready for a walk. Human children (before the age of reason) and unreflective adults react pretty much like my dog: impression > action.

However, thinking humans can do something more sophisticated, which is of crucial importance: we can give or deny “assent” to a given impression. That’s because we can interpose reflection in the above sequence, which then looks like this:

The sequence from assent to action or non-action, according to Stoic psychology.

For instance, I may receive the impression that I am thirsty, which, unreflectively, may generate the impulse to get up from my desk, go to the refrigerator, and grab a beer. However, I pause and reflect that drinking a beer at 11 in the morning, while I’m writing an essay for my Substack newsletter, is probably not the best idea in the world. I then decide either not to act on the impression, and instead continue writing for a bit longer, or to act in a different fashion, by redirecting my impulse toward a glass of water, as unexciting as it may be.

The power of assent distinguishes rational creatures from everything else in the cosmos, and according to Epictetus that power is the only thing that is truly up to us, and hence the only thing that clearly defines us as human beings. That is why the most important of the famous three disciplines in Epictetean ethics is called “of assent.”

The faculty that allows us to reason about things and consequently to give or not give assent to impressions is prohairesis, while the anatomical location of such faculty is the hêgemonikon, what Marcus Aurelius calls the “ruling center” of our mind (the famous “inner citadel” of Pierre Hadot). While the ancient Stoics thought the hêgemonikon resided in the heart (and they were severely criticized for that mistake by Galen, Marcus’s personal physician), we would nowadays say that it lies in the prefrontal cortex of the human brain, making possible what modern cognitive scientists call our executive function.

One more observation before closing with Stoic physics: all this talk of impressions, assent, and impulse to action makes Stoicism very much into a type of motivational cognitivism a la Socrates, and very much different from the position articulated by both Plato and Aristotle.

According to Socrates and the Stoics when we do something bad it is because we have made a reasoning error. Had we known better we would have acted appropriately.

Plato and Aristotle, by contrast, emphasized something the ancient Greeks called akrasia, or weakness of the will: sometimes we are motivated by non-rational sources of cognition, such as cravings and desires.

Both models appeal to me. On the one hand, it seems right to say that we suffer, at least occasionally, from weakness of the will. I talk myself into staying home and watching tv rather than getting my butt off the couch and going to the gym, even though I know that the gym would be the better option.

On the other hand, my behavior can also be interpreted within the Stoic framework: evidently, I don’t really believe that going to the gym is a better course of action, all things considered, because it involves giving up an activity I actually like in exchange for one I don’t enjoy. Yes, you may provide objective evidence that going to the gym increases my physical fitness, but physical fitness ain’t the only thing that matters in life, so there.

At the end of the day, one reason to prefer the Stoic model is because it aligns with modern cognitive science, which says that there is no sharp opposition between reason and emotions, since both are aspects of our cognition and can influence each other. After all, that’s the basis of the very successful cognitive behavioral therapy.

[Next time: ancient Stoic logic!]