The complex evolution of the Stoic "system"

Stoicism is, and has always been, a living philosophy in the making

The dream team of ancient Stoicism. Left to right: Zeno, Chrysippus, Seneca, Epictetus, and Marcus Aurelius. Image by Nano Banana.

I recently had the pleasure of participating to a roundtable discussion on whether Stoicism is a philosophy or a religion, and what to do with currently popular distortions of Stoicism, such as what I call “broicism.” The roundtable was organized by Jonny Thomson and Laura Kennedy, and featured my colleagues Nancy Sherman and John Sellars as well as myself. My assignment was to summarize the process by which the core doctrines of Stoic philosophy solidified, as well as how they changed from Zeno of Citium -- the founder of the school -- to Marcus Aurelius, the last great Stoic of antiquity.

Although I have previously published a double essay here at Figs which recounts both the eclectic origins of Stoicism and the subsequent innovations introduced by the Stoics, I think it will be useful to summarize what I said during that conversation. While my previous treatment of the topic was organized conceptually, this one is in historical sequence.

Zeno’s Stoa was not really a “school” in the formal sense of the term, akin to Plato’s Academy or Aristotle’s Lyceum. It was, rather, a living philosophical community more similar to the Garden of Epicurus, except that the latter was a private space outside of the city walls (just like both the Academy and the Lyceum), while the Stoa was everywhere people would gather to discuss philosophy as a way of life.

So, in the beginning, there was no codified system that one could call “Stoicism,” and followers were initially referred as “Zenonians.” Zeno did import a number of ideas from the various schools he had studied at: the notion that virtue is the only good from the Cynics (who in turn got it from Socrates); a sense of the importance of logic from the Megarians; and the four virtues (practical wisdom, courage, justice, and temperance) as well as the three disciplines of study (science, logic, and ethics) from Plato and the general philosophical milieu.

We know that some of Zeno’s students disagreed with more or less important details of his philosophy, so that we can tentatively conclude that there was no Stoic orthodoxy at the time, but rather a vigorous debate about how to live a eudaimonic life, a life worth living.

Then came Chrysippus of Soli, the third scholarch of the Early Stoa and arguably the foremost logician of antiquity. (Most people would assign that title to Aristotle, but that’s only because we lost almost everything Chrysippus wrote.)

Chrysippus saw that early Stoicism was a bit of a mess, precisely because it was a mishmash of different ideas taken from different sources. He set out to reorganize the whole thing, cleaning it up, purging, and making sure that the result was a coherent philosophy. He succeeded so well that the commentator Diogenes Laertius, in his Lives of the Eminent Philosophers, says that:

“If not for Chrysippus there would be no Stoa.” (7.183)

What did Chrysippus do? For one thing he articulated propositional logic and introduced the five fundamental, so-called anapodeictic (i.e., clearly demonstrable), syllogisms, a form of deductive argument whose conclusion is self‑evidently true -- that is, it expresses a proposition that is considered obvious or analytically necessary, such that denying it would be contradictory. In general, propositional logic is the basis of all modern logic and it was not surpassed until the end of the 19th century.

Still in the realm of logic broadly construed, Chrysippus also developed a unified theory of lekta, the so-called sayables, meaning what is expressed or meant by a utterance as distinct from the physical sound of the words, and also distinct from the external object the words refer to.

In science, Chrysippus proposed the theory of the tonos, the notion that different degrees of “tension” account for different kinds of unity in everything that exists: mere cohesion in stones and other inanimate objects, growth in plants, souls in animals, and reason in humans. In ethics, tonos describes the “tensile strength” of the rational soul, whereby a weak tonos is what allows passion and vice to take hold.

Also in ethics, Chrysippus reaffirmed the strict identity of virtue and the good; developed the concept of oikeiôsis, according to which we ought to work toward expanding our circles of ethical concerns beyond family, friends, and fellow countrymen, to include every rational being; and articulated the Stoic account of the emotions, distinguishing between healthy ones (eupatheiai) and unhealthy ones (pathe).

Chrysippus put a lot of emphasis on the figure of the Sage, the ideal human reasoner, who is the only one, technically speaking, who is virtuous and capable of knowledge, and therefore sets an essentially unreachable ideal for the rest of us. This notion, as we shall see in a moment, was rejected by the middle Stoics and set aside by all of the late Stoics except Seneca.

Part of what was going on at the time, incidentally, was a fascinating discussion between the Stoics, mostly represented by Chrysippus, and the Academic Skeptics, like Arcesilaus and Carneades. The Skeptics were, ahem, skeptical of the notion of absolute truth, preferring an epistemology that acknowledged the fallibility of the human senses and of reason. It appears that Carneades was so deeply engaged in this dispute that he said that if not for Chrysippus there would have been no Carneades. (Lives of the Eminent Philosophers, 4.62)

In 86 BCE, a dramatic political event altered the course of Western philosophy: during the the First Mithridatic War, the Roman general Sulla entered into Athens and sacked the city. This led to a diaspora of philosophers, several of whom relocated to a number of emerging cultural centers throughout the Mediterranean, including Rhodes, Alexandria, and Rome.

This is the period of the Middle Stoa, characterized by the figures of Panaetius of Rhodes and his student Posidonius of Apamea (who in turn was one of Cicero’s teachers).

Panaetius was the first to question the usefulness of the concept of the Sage, so dear to Chrysippus. He emphasized the notion of kathêkon, or appropriate action, as the practical ethical target for non-sages: one doesn’t have to be a Sage in order to act “appropriately.” Cicero, whose De Officiis was influenced by a now lost book by Panaetius, translated the term as “duty” (officium) and developed his system of personal ethics on that basis.

Panaetius also downplayed the famous conflagration cosmology in Stoic science, originally imported from the metaphysics of the Presocratic Heraclitus, and absorbed elements of Plato and Aristotle, such as -- respectively -- the idea of a spirited part of the soul and the value of natural advantages (what the Stoics called “indifferents”).

Posidonius went even further -- sometimes in the wrong direction, in my opinion. Influenced by Plato’s Republic, he rehabilitated a tripartite psychology whereby the passions have their own (irrational) seat and they are not treated just as cognitive misfirings. These are not minor tweaks but a significant revision of Chrysippan psychology and axiology, which means that the Stoa was already pluralist long before the Romans arrived.

The Romans, representing the Late Stoa, include of course Seneca, Epictetus, and Marcus, but also Hierocles (author of the largely lost Elements of Ethics) and Musonius Rufus (Epictetus’s teacher).

There is a palpable shift at this point from system-building to spiritual practices in the sense articulated by French scholar Pierre Hadot. And there are marked differences among the three big Roman Stoics.

Seneca is eclectic and literary, openly borrowing from Epicurus in his Letters to Lucilius. Ethics for him is primary and science largely instrumental, though he does write Naturales Quaestiones, which is a book on natural philosophy.

Epictetus in a sense returns to a more rigorous Chrysippan core centered on the concepts of prohairesis (our faculty of judgment) and eph’ hêmin (what is up to us). However, the Discourses are decidedly therapeutic, not theoretical, with the Stoic logos becoming primarily a tool for self-governance. Indeed, while Epictetus explains to his students the importance of studying logic (Discourses 1.17), he also warns them that if all they do is to engage in the exegesis of Chrysippus they are no better than literary critics (Enchiridion 49).

Finally, Marcus is arguably the most heterodox of the Stoics. He uses Platonic language throughout the Meditations (for instance, at 4.3) and he expresses genuine uncertainty about cosmology (with his famously recurring “atoms or providence?” trope, also in 4.3). The tone is one of effort and struggle, with not a shred of Chrysippan confidence. Which, a bit paradoxically, means that the most famous Stoic of all may have been the one least committed to Stoic orthodoxy -- whatever that is.

So what we call ‘Stoicism’ is really a family of overlapping philosophical commitments held together by a shared vocabulary and a shared ethical orientation -- the doctrinal core was always contested and always evolving. That is perhaps itself a Stoic lesson: philosophy as a living practice resists final systematization.

[Next time: Five crucial Stoic ideas.]