Stoic Physics isn’t Rocket Science

Part 2: Rock That Body

After having looked very briefly at the general system of Stoic physics and cosmology in part 1, and how it forms the basis for Stoic ethics, today I’d like to get a bit more into the nitty gritty of Stoic causality.

Let’s get physical!

We already noted that the Stoics were so-called physicalists, i.e. they stated that only “bodies” exist. These “bodies” are three-dimensional and solid, as Diogenes Laertius writes:

“Body is defined by Apollodorus in his Physics as that which is extended in three dimensions, length, breadth, and depth. This is also called solid body.” — Diogenes Laertius, Lives of Eminent Philosophers [7.135]

In other words, according to the Stoics everything which exists in the universe are bodies, including the cosmos itself, its two major principles (active and passive) and everything in it.

While the characteristics of “three-dimensional” and “solid” may seem straightforward at first, the Stoic bodies are something entirely different than our contemporary understanding of objects in three-dimensional space would suggest.

For example, the fact that the Stoics also identified the soul, emotions and thoughts as “bodies” should make us wonder. After all, how can we understand the length of love, the breadth of sorrow, and the depth of joy not just in a temporal but in a physical sense? That seems a little strange.

What’s the weight of a feeling?

This idea that only bodies exist is often understood as a direct reaction of the Stoics to Plato and his dualism of ideas versus matter. Not only did the Stoics reject Plato’s assumption that the soul was immaterial and immortal (an idea that greatly influenced Christianity), they also understood virtue, divinity (logos) and truth itself as “material” bodies. How is that possible?

In a nutshell, Stoic bodies aren’t just things which can be touched, but instead things which interact causally, i.e. they affect and are affected by other bodies. This is due to these bodies’ aforementioned solidity which seems to have been understood as a kind of resistive potential. For example, when you smack one billiard ball into another one, they react and move because of their solidity. If they weren’t solid they would just glide through one another without any effect. Similarly, because thoughts or emotions can affect or be affected by other things, they are therefore considered bodies.

One way to understand this is that in many languages we frame emotional affect in terms of “movement”. We say: “That was a moving speech, book, film, conversation, etc.” But what exactly is being moved here? Did your emotional center change its x,y,z coordinates? And what caused this shift? We’re quick to point out that we don’t mean this literally. But in which space does this movement take place? Instead of creating another metaphysical plane for immaterial entities the Stoics placed all of these in the same “physical” universe; because both the idea, sentiment or artifact and your emotional reaction are bodies: billiard balls crashing into one another.

The Christian philosopher Nemesius (ca. 390 CE) quotes the Stoic Cleanthes in this striking passage from De Natura hominis:

He [Cleanthes] also says: no incorporeal interacts with a body, and no body with an incorporeal, but one body interacts with another body. Now the soul interacts with the body when it is sick and being cut, and the body with the soul; thus when the soul feels shame and fear, the body turns red or white respectively. Therefore, the soul is a body.” — The Hellenistic Philosophers, Vol. 1: Translations of the Principal Sources, A.A. Long, p. 272

In the same manner, the quality of one’s character has “solidity” in the Stoic sense, because it affects how we speak or act, which emotions we experience and how we are affected by them. This has huge ramifications for Stoic ethics. Contrary to Aristotle who understood physics and ethics as two independent fields of study, the Stoics saw the study of physics as an integral component of ethics and vice versa.

For example when we look at the character of the sage, the Stoic ideal of moral excellence, it quite literally was understood to have a different solidity, i.e. resistive potential than that of regular people.

Sextus Empiricus, while being very critical of the Stoics and the unattainable ideal of the sage, still summarized this “solidity” of character correctly:

“The sage possesses an infallible criterion, which makes him in all respects divine because he never holds opinions, that is assents to what is false, wherein lies the height of unhappiness and the ruin of the inferior person.” —Sextus Empiricus, Against the Professors” (7.423):

In other words, so-called apatheia or unhealthy emotions don’t affect the sage at all. His inner state of cohesiveness or integrity of character is so solid that these “opinions” (also bodies) don’t cause any change or harm in him. Whereas the regular person is affected by all kinds of fleeting thoughts and emotions, the sage instead affects them, e.g. by “withholding assent” and essentially making them ineffectual.

While this is not the place to evaluate the notion of such an unattainable ideal within an ethical framework, it’s still worthwhile to note how our state of mind, to use a modern term, is understood as a body due to its resistive potential or solidity.

Empirical Evidence Has Entered The Chat

Interestingly, modern evidence based approaches to psychotherapy, such as cognitive behavioral therapy (CBT) or its precursor, rational emotive behavior therapy (REBT), are based on the same principle: that our thinking affects our feelings and behavior in a very fluid and interrelated way. They act and are acted upon another causally:

“REBT assumes that human thinking, emotion, and action are not really separate or disparate processes, but that they all significantly overlap and are rarely experienced in a pure state. Much of what we call emotion is nothing more nor less than a certain kind — a biased, prejudiced, or strongly evaluative kind — of thought. But emotions and behaviors significantly influence and affect thinking, just as thinking influences emotions and behaviors. ” —Albert Ellis (2003), Journal of Rational-Emotive & Cognitive-Behavior Therapy, 21(3/4)

In other words, these forms of therapy seem to confirm the core premise of Epictetus that “it’s not things that upset us, but our opinions of things”. Or as Shakespeare stated in Hamlet: “there is nothing either good or bad, but thinking makes it so”.

Contrary to Freudian psychotherapy, CBT and REBT have consistently been proven to be effective in empirical studies, i.e. these methods actually help people to overcome their anxieties, depressions, addictions, etc. Perhaps not surprisingly their founders have noted ancient philosophy in general and Stoicism in particular as an inspiration. (I highly recommend Donald Robertson’s The Philosophy of Cognitive Behavioural Therapy for a more in-depth look into this.)

So, in an indirect way, the ancient Stoic idea that our thoughts, feelings and behaviors are bodies, which seems somewhat ludicrous at first glance, actually holds up to empirical scrutiny. Mind-boggling, isn’t it?

To summarize, everything which exists in the Stoic conception of the cosmos is bodies. If it affects or can be affected, it’s a body. Causality happens only between bodies, with a small exception: the Stoics did recognize non-physical entities as well, such as emptiness, place, time and the utterable, which can affect causality between bodies while not being bodies themselves (we’ll have to look at these at another time).

I hope you’ve found this article helpful. In the next part of this series on Stoic physics, I’d like to talk a bit more in detail about the anatomy of these bodies, how they were understood to mix and and permeate one another.