[A few weeks ago I was asked by Greg Sandler, together with several other members of the Modern Stoicism project, to write a short piece on how I conceive of the contemporary version of our philosophy. Below is my entry, annotated with links, and here are the other six responses, by the likes of Chris Gill, Don Robertson, Piotr Stankiewicz, Tim LeBon, Greg Lopez, and Bill Irvine.]

Ludwig Wittgenstein taught us that no interestingly complex concept can be reduced to a small set of necessary and jointly sufficient conditions in order to be precisely defined. His example was that of “games.” Try and see if you can come up with a compact definition of what a game is and include every activity that normally falls into that category, while at the same time excluding everything else. It’s impossible. For every criterion you can think of (it’s done for fun!, it has rules, it’s a competition) there will be exceptions both ways: some games will fail to satisfy the criterion (solitaire is not competitive), while some non-games will meet that same criterion (your job may be competitive, but that doesn’t make it a game). Even so, Wittgenstein argued, we know what does and does not count as a game, though we can have meaningful discussions about borderline cases (war “games”?).

I believe something like that applies to the distinction between Ancient and Modern Stoicism, with one important caveat to be discussed shortly. There is what Wittgenstein called a “family resemblance” between the two versions of Stoicism, meaning that they sort of look alike and yet are not the same, like a daughter and her mother. And just as in the case of human families, there is a line of (cultural) descent connecting one to the other,

Unlike other philosophical traditions, say Buddhism, Stoicism has not evolved continuously: its development was “interrupted” by the decline of Hellenistic philosophies and the rise of Christianity, and although Stoic ideas have influenced plenty of philosophers since (including many Christian ones), we pretty much jumped from the 2nd to the 20th century with little in between (except for the brief interlude of Renaissance “Neo-Stoicism”). The world we live in now is in some respects very different from that of the ancient Greco-Romans (they didn’t have internet and social networks!), though in other respects it’s pretty much the same (Seneca, in Letter 56.1 to Lucilius, complains of unbearable noise coming from the street, which made it difficult for him to write — I can relate).

There are, accordingly, a number of notions from Ancient Stoicism that I think are negotiable for Modern Stoics. The idea of the universe as a living organism characterized by diffuse intelligence (the Logos), for instance, with its corollary of pantheism and the concept of a “providence” that, though very different from the Christian concept, still sets things in the best possible way at a cosmic scale. I think that a Modern Stoic can be a pantheist, a theist, an agnostic, or an atheist, and still arrive at a reasonable reconstruction of what the Logos means (elemental consciousness, the word of God, the logical structure of the laws of nature).

Much of Stoic “physics,” of course, has been superseded by modern science, and it won’t do for us to cling to notions that are contradicted by the advancements in human knowledge of the last 18 centuries. We know a lot more than Posidonius and Seneca on eclipses and comets. Fortunately, the details of Stoic physics underdetermine the important bit, Stoic ethics.

Even Stoic logic, as groundbreaking as it was at the time, and as influential as it was until the 19th century, has been surpassed by its modern counterpart, especially if we don’t limit ourselves to formal logic, but broaden the scope of the field in the way the ancient meant, to include every aspect of human reasoning (and hence cognitive science, applied psychology, even neuroscience).

Politically, some Stoics were what we would call “conservatives” (Hierocles), others were pragmatists (Marcus Aurelius), and some were (somewhat) “progressive” by the standard of the time (Musonius Rufus, who advocated teaching philosophy to women). So Modern Stoics may also come from pretty much across the political, not just the theological, spectrum. (There are some exceptions: I’m pretty sure racism is not a Stoic value, for instance.)

All of the above said, one could reasonably ask whether “Stoicism” is then such a flexible concept that pretty much anything, or almost anything goes. I don’t think so, and here comes the aforementioned caveat, the exception to a Wittgensteinian view of the relationship between Ancient and Modern Stoicism. If there was one thing I would have to pick that I believe defines the core of Stoicism, and without which it begins to make little sense to call oneself a Stoic, is the primacy of virtue over externals (or “preferred indifferents”). “Happiness,” meaning eudaimonia, the life worth living, for a Stoic means a life of as much moral integrity as one is able to muster. Everything else, including material things, and even relations, is secondary. Not in the sense that it is to be discarded (we are not Cynics!), but in the sense that it can never be traded off with virtue. Why? Because we want to live according to nature, which especially in a modern context just means to take seriously the two fundamental characteristics of humanity: we are social animals capable of reason.

So, as Marcus puts it “Do what is necessary, and whatever the reason of a social animal naturally requires, and as it requires” (Meditations IV.24).