Stoicism, like the other major ancient intellectual movements of antiquity, is dubbed a “school.” The word “school” implies a shared tradition of belief and practice, not necessarily a shared physical location, but it does not necessarily imply total agreement on every point of doctrine. Our (fragmentary and inadequate) evidence for Greek Stoicism suggests that there were a number of shifts of focus and belief over the course of the movement’s history. Scholars usually distinguish between the early period and the Middle Stoa (although there is less of a gap between the early and middle periods than was once thought), and then the Roman period, characterized by an increased interest in ethics. Moreover, adherents to Stoicism often held different views from one another even in a single period. Seneca was an eclectic thinker; despite identifying primarily with Stoicism, he draws on many other traditions. Adherence to a school did not imply that a person would take all aspects of dogma as already predetermined by that school’s traditions: a philosophical movement was not a faith. Seneca was also an original and creative thinker who made significant new contributions to Stoic views of psychology.
Despite all these caveats, some central notions were common to Stoic belief throughout its history and among all its adherents, including Seneca. The Stoics believed that the whole world is governed by universal Reason or Fate or God or Providence, also identified as Jupiter or Zeus, and associated with primordial Fire, which guides all of nature. “Any name for him is suitable,” as Seneca says: “You can’t go wrong” (Natural Questions 2.45.2). According to Stoic physics, the cosmos has a cyclical pattern: at regular intervals everything is destroyed by fire (ekpyrosis) and then remade again (palingenesis). Nature was not merely inert or purposeless; rather, the whole universe followed a fixed, predetermined, and always benevolent pattern. It is always in the best interests of humanity to follow nature, because nature is always good. Despite a firm belief in Fate, the Stoics emphasized individual decisions, since we always have a choice about whether we conform our will to the will of the universe, or resist. In Seneca’s imagery, the wise person, who conforms his desires to those of God, becomes the follower of God; the foolish person, who fails to conform to what must be, is merely His slave (On Providence 5.6–7).
Virtue and knowledge are thus closely connected. The Stoics challenged the view common among other philosophical movements in antiquity (such as Platonism) that the human soul includes both rational and irrational elements. For them, human beings are a complete whole, not a collection of diverse parts, and that whole is entirely rational—although people are prone to false reasoning and mistaken beliefs. It is a failure of reason that makes us liable to unhappiness and wrongdoing. For the Stoics, if we always thought properly and managed to perceive the truth, we would never do wrong or be unhappy. This helps to explain the central place of logic in the Stoic system. The Stoics believed that humans are entirely capable of understanding the universe, and also that human happiness depends on our ability to think properly. The ideal is to align our own minds with the rational will of the universe. The Stoics were sophisticated logicians who made many advances in formal logic; in antiquity, those hostile to the school often mocked them for their abstruse reasoning and fondness for paradox.
Ethics was and is the most challenging area of Stoic philosophy—the most inspiring or the most infuriating, depending on one’s point of view. The Stoics had, as we have seen, a notion of the “wise man.” I use “man” deliberately because for most Stoics and Stoic-sympathizers, including Seneca, there is a strong assumption that the ideal wise person will be male, and that there is a correlation between virtue (in Latin, virtus, “manliness”—from vir, “man”) and masculinity—although a few Stoics, most notably Musonius Rufus, a younger contemporary of Seneca, seem to have questioned this association and argued that women are quite capable of learning to be philosophers.12
The wisdom of the Sage consists in the fact that he knows, fully and at every moment, that virtue alone is sufficient for happiness: everything else, including pleasure, pain, health, wealth, and freedom, is “indifferent.” This virtuous wisdom is an all-or-nothing proposition: the Sage is always, at every single moment, acting virtuously and in possession of all the virtues. Even when doing apparently normal things that might not look especially virtuous—eating dinner or taking a bath—the sage is always acting with wisdom, courage, temperance, and justice. Conversely, those who are not sages can never act virtuously; even when they may seem to be doing something good (like saving a child from a fire) or neutral (like eating dinner), the non-sage is always in a state of vice. Moreover, only the Sage is free and self-sufficient; everybody else, even when they seem to be making their own choices, is actually in a constant state of metaphysical enslavement. The Stoics cited the metaphor of a person drowning: it makes no difference whether his head is ten feet under water or only an inch; any amount of water above your head is enough to stop the breath (Plutarch 61T).
All this is, of course, very paradoxical, and it is not hard to see why Stoic ethics were widely mocked. The Stoics themselves acknowledged that the true Sage is very rare, possibly nonexistent; it is, after all, difficult for a human being to be perfectly virtuous and perfectly wise. One may well wonder, then, what practical purpose is served by the ideal. If a person who is utterly depraved is no worse in relation to true virtue than one who has just a few faults, then why would one ever try to improve? What would improvement even mean, if virtue is something you either have or you don’t?
But the Stoics allowed a great deal of room in their system for improvement and education in the path toward virtue. Crucially, they distinguished between performing a “correct function,” kathekon, and performing a “fully correct action,” katorthoma. The former includes any kind of action that is in accordance with nature (such as eating or breathing or exercising in appropriate ways); correct functions can be performed by plants and animals as well as non-sage humans. The non-sage can train himself (perhaps with the help of a philosophical tutor or teacher) to perform more and more correct functions and to come closer and closer to full realization of the true nature of the universe. He may still die before attaining the status of a sage, but the attempt to come somewhat closer to the surface of the water is itself a worthwhile goal.
Many complained (as did, jokingly, the satirist Lucian) that Stoics were entirely out of touch with the practicalities of daily life.13 One may accept in theory that it is more important to be a good person than to have a lot of money, but, given the choice of wealth or abject poverty, most of us would rather be rich. The Stoics took account of this in their theory and allowed for a category in between the things that are absolutely good and bad: the “indifferent things.” The Stoics were able to acknowledge that, all things being equal, it is preferable not to be tortured, imprisoned, enslaved, impoverished, dishonored, die, have one’s loved ones die, or suffer a painful or debilitating illness. Epictetus tells us, “Of things that exist, some are good, some are bad, others are indifferent. Good things are virtues and everything that shares in virtues; bad things are the opposite; and indifferent things are wealth, health, reputation” (Discourses 2.15). The indifferent things are incommensurable with the value of virtue, such that any amount of torture would be better than any amount of vice. The Stoics insist that, even under torture, even while having his limbs cut off, even while being enslaved, even under the greatest humiliation, the Stoic Sage will be happy and free, living the ideal life as long as his virtue remains intact. The promise of Stoicism, in which lies much of its attractiveness, is that one can be guaranteed a life of pure joy, if only one can attain the correct attitude toward the universe. The Stoic—unlike the “stoic,” in contemporary, nonphilosophical usage—will not repress feelings of anxiety, rage, or pain: he will not feel troubled by any of them, and indeed, he will be objectively unhurt by any of them. He is, in Seneca’s terminology, not merely above bad feelings but immune from all actual injuries (see, e.g., On Constancy, 3.1–4).