Determinism, swerves, and the relationship between metaphysics and ethics

An ancient debate on the nature of the world is still with us, and for good reasons

The Epicurean Roman poet Lucretius, Wikimedia.

Last weekend I taught an intensive online seminar—eight hours total—on Socrates as seen by Xenophon. We read and discussed the Memorabilia, which presents a lively portrait of the sage from Athens, with Socrates freely giving advice to wannabe politicians as well as courtesans. It is also, incidentally, the book that inspired Zeno of Citium to get into philosophy, and therefore indirectly led to the founding of Stoicism.

At some point we got into a discussion on the relationship between metaphysics—how we think the world works—and ethics—how we think we should behave in the world. The Stoics argued that the two are tightly related: to live ethically means to live “in agreement with Nature,” and to do the latter we need to understand Nature. Turns out, though, that the Stoics were not the only ones to connect metaphysics and ethics. So did their arch-rivals, the Epicureans, though the latter posited a different metaphysics and arrived at a different ethics.

Perhaps not surprisingly, the basic framework of the debate is still with us today. And so are the available options to resolve the debate, despite more than two thousand years of intervening philosophy and quite a few centuries of modern science. Here, then, is yet another chance to dive into Greco-Roman thought not just as a historical curiosity, but because it could change the way we look at the world and at our place in it.

Let us start by comparing and contrasting Stoic and Epicurean metaphysics, then we’ll examine a couple of major consequences the two views have for ethics. And finally I’ll make some comments about what this means for us denizens of the 21st century.

The first thing to appreciate about both the Stoics and the Epicureans is that they consciously kept their metaphysics very near their epistemology, that is, they made sure to have good evidence for whatever metaphysical view of the world that was being advanced. I wish I could say the same for modern metaphysicians like David Chalmers and Philip Goff. But I can’t.

The Stoics, epistemologically speaking, were a combination of rationalists and empiricists: they paid attention to the world as it is by way of observation, but also put a premium on the ability of the human mind to arrive at new inferences, sometimes in spite of direct sensorial evidence. For instance, consider what you see when you partially submerge a pencil in water. It seems to be broken at the point of immersion. But the Stoics rejected the immediate verdict of the senses and deployed the mind to grasp the reality that the water only appears to cause the breaking of the pencil. Sure enough, today our minds understand that the phenomenon is caused by the different refraction properties of water and air.

Zeno of Citium, the founder of Stoicism

The Epicureans, by contrast, were more markedly empiricists, and therefore openly skeptical of the power of reason. They arrived at this conclusion on the basis of the fact that too often human reason makes erroneous leaps and lands in treacherous waters. Better stick with the evidence of the senses, which they thought was infallible. Every instance of fallibility by the senses was actually attributed to the interference of the mind and could be corrected only with further input from the senses. In the case of the apparently broken pencil, for instance, all that one needs is to deploy the sense of touch and realize that there is no actual breaking or bending of the pencil.

On the basis of their different epistemologies, Stoics and Epicureans arrived at starkly diverging views of the world. For members of the Stoa, the universe is a living being endowed with reason, and everything within the universe is designed by a vast intelligence. For members of the Garden, instead, the universe is the result of tiny invisible particles, the atoms, bumping into each other to create the objects we see at the macroscopic level. How did they get there?

The Stoics deployed what we today call an argument from design, which basically begins with the observation of complexity and function in the world—think of the human eye, which appears to be engineered in order for us to see things—and infers the existence of a supreme designer, God.

We find one version or another of this argument in Socrates, Plato, Aristotle, Cicero, and Epictetus, among others. That is, in almost all the Greco-Roman thinkers, not just the Stoics. Here is how Epictetus puts it:

“Who is it that has fitted the sword to the scabbard and the scabbard to the sword? Is there no one? Surely the very structure of such finished products leads us commonly to infer that they must be the work of some craftsman, and are not constructed at random. Are we to say then that each of these products points to the craftsman, but that things visible and vision and light do not? Do not male and female and the desire of union and the power to use the organs adapted for it—do not these point to the craftsman?” (Discourses, I.6)

Image from romegiftshop.com.

Had I been alive at the time, instead of after David Hume and Charles Darwin, I would likely wholeheartedly agreed with Epictetus & co.: the universe is intelligently designed, and we can arrive at this conclusion with confidence on the basis of a straightforward inference that takes as premise a number of obvious observations about the structure of the world.

Of course, as a modern scientist who can avail himself of the pointed critique of intelligent design articulated by Hume, and more importantly of the alternative explanation for complexity and adaptedness advanced by Darwin, I reject the argument from design and in fact think that its modern practitioners are a bunch of religiously motivated purveyors of pseudoscience.

How did the Epicureans arrive at the conclusion that, on the contrary, the world is made of atoms bumping into each other in the void? Among their observational sources for this inference was—as the Roman poet Lucretius tells us in his De Rerum Natura (On the Nature of Things)—the fact that objects are gradually wore down: rings by constant use, roads by being trampled on, stones from the protracted dripping of water, and even statues that are repeatedly kissed. The only logical explanation for these gradual degradations is that such objects are made of tiny particles, some of which keep being washed off by various activities. Clever, no?

Would I have found the Epicurean arguments compelling, had I lived at the time? Probably. But then I would have had to face that non trivial problem of reconciling atoms in the void with the highly orderly structure of the Stoic cosmos. Of course, the two views are not strictly incompatible: one could postulate an intelligence outside of the universe (thereby moving from pantheism to theism), which sets up the laws of Nature so that the macroscopic world we observe results from the movements of atoms. That, basically, is how modern Christian theologians who are not fundamentalist nutcases manage to see no contradiction between their faith and contemporary science. Frankly, however, to buy into that scenario takes more mental gymnastics than I’m capable of, but that’s a different conversation for another time.

Before we move on to the ethical consequences of the Stoic and Epicurean worldviews, I need to point out a fact that is often overlooked or even not understood at all: both schools embraced a deterministic metaphysics. This is obvious in the case of the Stoics: they believed that everything is made of matter, and that everything is subject to the laws of cause and effect. In modern parlance, they were both materialists and determinists.

The Epicureans also thought that everything is made of matter, in the form of atoms of various sizes and shapes. These atoms—with one gigantic exception to which we’ll get to in a few minutes—moved in straight, predictable lines. That also is determinism. So the two schools were far closer to each other than one might initially suspect.

It is now time to look at two major ethical consequences of Stoic and Epicurean metaphysics: the concept of (Stoic) Providence, or lack thereof (for the Epicureans); and the (Epicurean) concept of free will, or lack thereof (for the Stoics).

One of the remarkable things about this story is that such similar metaphysical stances—again, both schools are materialistic and deterministic—can lead to radically different implications, though I think the reason for this outcome is that the Stoics were more coherent than the Epicureans when it came to the connection they perceived between metaphysics and ethics.

Let’s begin with the notion of Providence. Both Stoics and Epicureans believed in the existence of gods. For the Stoics, god is the same as fate, which is the result of the laws of cause and effect (Diogenes Laertius, Lives of the Eminent Philosophers, VII.136). God / the Cosmos is also a living being (DL, VII.147) endowed with reason. From this it follows that whatever happens to us is for the good of the cosmic / divine organism. Which means that we should not just accept and endure our fate, but actively embrace it. Amor fati, as Nietzsche said much later on.

Think of it this way: we are like cells of the cosmic organism. A cell can only regret its fate, say its short lived life, if it looks at things in isolation. But if it understands that the purpose of its existence is to insure the wellbeing of the whole organism, then it will be happy to do its part. This is an incredibly comforting thought, and makes sense of the otherwise disturbing words of Epictetus:

“If you kiss your child or your wife, say to yourself that it is a human being that you’re kissing; and then, if one of them should die, you won’t be upset.” (Enchiridion, 3)

For Epicurus, by contrast, the gods are perfect intellectual beings who live far away from us and simply do not concern themselves with human affairs. It follows that there is no sense of Providential fate in Epicureanism. Whatever happens is the result of the mechanics of the universe, and it has nothing to do with the will or wellbeing of the gods.

In his Letter to Herodotus, Epicurus says that the gods do not control natural phenomena—which would make them imperfect—and that therefore we shouldn’t pray to them nor be afraid of what they might do. Indeed, superstition and the fears it engenders get in the way of the Epicurean goal of ataraxia, or tranquillity of mind. Therefore, Epicureans cannot avail themselves of the comforting thoughts articulated by Epictetus: when your wife or child dies it sucks, you suffer pain, and your quest for ataraxia suffers a serious setback.

Epicurus, Wikimedia

What about free will? Here too the two schools differ dramatically. The Stoics reject the notion of free agency, a logical result of their belief in universal cause and effect:

“They too [Zeno and Chrysippus] affirmed that everything is fated, with the following model. When a dog is tied to a cart, if it wants to follow it is pulled and follows, making its spontaneous act coincide with necessity, but if it does not want to follow it will be compelled in any case. So it is with men too: even if they do not want to, they will be compelled in any case to follow what is destined.” (Hippolytus, Refutation of All Heresies, 1.21)

Hard to imagine a more stark metaphor for causal determinism. However, the Stoics also insist that our judgments and decisions to act or not to act are, as Epictetus puts it, “up to us.” How can this be, if we live in a deterministic world? Because the Stoics are what modern philosophers call compatibilists: they think that there is no contradiction between the fact of determinism and the fact (because it is a fact!) that we are capable of volition, that is, decision making.

This makes sense once we reject simplistic caricatures of compatibilism a la Sam Harris’s The Moral Landscape, where human beings are like puppets whose strings are controlled by external events. More logically, the Stoics think that we—including especially our faculty of judgment—are part and parcel of the cosmic web of cause and effect, not its hapless victims. Which means that some of those causes are internal to us, the result of our own decision-making machinery, which Epictetus referred to as our prohairesis, or will.

The resulting picture is very different from that of the Epicureans. The latter claim that we observe free will every time we make a decision, and that too much thinking about it leads us away from the only reliable source of evidence, our own senses. But then they face the problem posed by their embracing two seemingly entirely incompatible notions: a hard position on determinism, and yet a defense of true free will.

Unlike the Stoics, the Epicureans very clearly distinguish three types of causes, as Epicurus says in his Letter to Menoeceus: “Some things happen of necessity, others by chance, others through our own agency.” (This, incidentally, is not an original position, as it can be found earlier in Aristotle.)

The Stoics, by contrast, only recognize necessity. For them, chance is a word we use when we do not have sufficient knowledge of the causes of things. And true agency (as opposed to agency-as-part-of-cosmic-cause-and-effect) is an illusion.

Here is where the Epicureans made a fatal mistake. Unable to let go of true free will they had to introduce what modern philosophers of science would call an ad hoc hypothesis: the famous swerve, or clinamen in Latin. Lucretius explains how this is supposed to work:

“When atoms move straight down through the void by their own weight, they deflect a bit in space at a quite uncertain time and in uncertain places, just enough that you could say that their motion has changed. But if they were not in the habit of swerving, they would all fall straight down through the depths of the void, like drops of rain, and no collision would occur, nor would any blow be produced among the atoms. In that case, nature would never have produced anything.” (De Rerum Natura, II.216–224)

Lucretius continues: “It is this slight deviation of primal bodies, at indeterminate times and places, which keeps the mind as such from experiencing an inner compulsion in doing everything it does and from being forced to endure and suffer like a captive in chains.”

There are two huge problems with this move: (a) we are never told how swerves come about; and (b) we are also not told how swerves end up triggering free will. In other words, the swerve is one of the greatest blunders of ancient metaphysics.

To recap: the Stoics were coherent in their metaphysics, its connection to their epistemology, and its implications for ethics. The Epicureans also produced a coherent metaphysics justified by their epistemology, but insisted on an idea, true free will, that didn’t fit at all with their system and forced them to introduce an arbitrary phenomenon for which they had no independent evidence or explanation.

All of the above said, where do we stand today? What does modern science, the ultimate ground for any rational metaphysical system, tell us about determinism, causality, Providence, and free will? And what are the implications of the scientific worldview for our understanding of ethics?

A full treatment would make this a very long essay, and at any rate I’m reasonably confident I will return to these issues again in the future. But the bottom line, in my understanding, is this:

(i) We don’t know whether we live in a deterministic universe or not. Quantum mechanics seems to suggest that there are truly random physical phenomena, such as the spontaneous decay of atoms. Then again, the equations that describe the theory are fully deterministic. And at any rate we already know that quantum mechanics is not the fundamental theory in physics. So: agnosticism is recommended.

(ii) We do know, however, that at the macroscopic level of human action everything seems to happen by cause and effect, no exceptions. (They would be called miracles, and they don’t happen, as far as we can tell.)

(iii) Because of (ii) “free will” in the strong Epicurean sense does not exist. And neither do swerves. It appears that the Stoics were right: whatever is “up to us” is such only in the specific compatibilist sense that we are part, and do not stand outside, of the cosmic web of cause-effect.

(iv) The cosmos is not a living organism endowed with reason, and therefore Stoic-type Providence is out of the question. The Epicureans were right: we just need to endure life and do our best, there is no room for amor fati.

In the end, both the Stoics and the Epicureans were right that our understanding of the world (metaphysics, science) informs how we think we should behave in the world (ethics). Which is a very good reason to take both very seriously.