What is Stoicism? by John Sellars

In what follows I want to set out some key ideas in Stoicism. My aim is to say something about the philosophical ideas that stand behind all those inspirational quotes from Seneca and Marcus Aurelius that circulate on the internet. What are the foundational principles of Stoicism as a philosophy?

I shall start by saying something about how the ancient Stoics understood their philosophy. According to the ancient Stoics, Stoicism is a philosophy with three parts: logic, ethics, and physics. Most of them insisted that these three parts form an integrated whole and they used some nice imagery to try to illustrate this. Stoic philosophy is like an egg, they said: logic is the shell, ethics is the white, and physics is the yolk. Or it’s like an orchard: logic is the enclosing wall, physics is the trees, and ethics is the fruit. Or again it’s like a human being: logic is the bones, ethics is the flesh, and physics is the soul.

In each case, the point they want to make is that these three parts of philosophy form an integrated whole. You can’t have an egg or an orchard or a human being without all three parts. You need all of them. So, what I’m going to do is say a bit about each of the three parts, pick one key concept from each, and say something along the way about how they connect together.


Let’s start with logic. By ‘logic’ the Stoics mean something much broader than the way we tend to use that word today. I think the best way to characterize it is to say that it’s concerned with knowledge: it’s concerned with what we can know, with what we say, the truthfulness of what we say, and the logical consistency of the arguments we make. So, it includes what we now think of as logic, but it’s also much wider than that.

The Stoics – like many other ancient philosophers – think rationality is one of the defining characteristics of human beings, so they place great emphasis on logical consistency. Indeed, so do most of us, even if we might not always be aware that we are doing so. It’s not uncommon, for instance, to hear people criticize others for being inconsistent, as if inconsistency is simply an inherently bad thing. None of us like hypocrites, or people who say one thing one moment, only to contradict themselves moments later. This idea of consistency will crop up a number of times in the rest of what I’m going to say.


There’s so much that we could say about Stoic logic, but I want to focus in on just one key idea that comes from this part of Stoic philosophy. It’s the idea of judgements. According to the Stoics our judgements are the foundation for all of our knowledge. We receive information via our senses, it’s presented to our mind, and we make a judgement about it – to accept it or to reject it – and this creates a belief. Sometimes we make good judgements and sometimes we get it wrong. This is obviously important for simply understanding the world. But something that the Stoics also stress is that we don’t just make judgements about matters of fact, we also make value judgements, and those value judgements shape our lives. We pursue what we think is good, try to avoid what we think is bad; we feel happy when we get what we think is good, and frustrated when we can’t. Our emotional lives are effectively the product of the judgements we make.

Let’s look at a couple of short quotes. Very famously, Epictetus wrote:

It’s not things that upset us but our judgements about things. (Epictetus, Handbook 5)

And Marcus Aurelius touched on the idea when he wrote:

Don’t say more to yourself than first impressions report. You have been told that someone speaks ill of you. That’s what you’ve been told; you have not been told that you were harmed. (Marcus Aurelius, Meditations 8.49)

So, the first task, according to the Stoics, is to pay attention to our judgements. All too often we make judgements quickly, unthinkingly, almost unconsciously. Instead the Stoics suggest we ought to slow down, try to open up some cognitive distance between the moment we experience something and making a judgement about it. This could apply to hastily accepting some dubious news story on social media or reacting angrily to a perceived insult. In both cases, pausing before rushing to judgement will enable us to respond in a more measured and appropriate way. This is why judgement is a key concept for the Stoics.


This leads us to the next part of Stoicism: ethics. If logic is ultimately about knowledge, then ethics is primarily about value. It’s concerned with what’s good and bad, and what we ought to do and not do. Many people curious about Stoicism today may think they are only interested in the ethics, but as I’ve already tried to show, the logic is essential too, especially the role played by our judgements. In the second passage we looked at a moment ago, Marcus Aurelius effectively says that if someone speaks ill of you, nothing bad has happened. If you judge that something bad did happen, you’ve made a mistake. So why does Marcus think that being spoken about in unpleasant terms is not a bad thing? This opens up the question of what does and does not have value, and it’s going to introduce the key concept in ethics that I want to focus on: virtue.


What’s good and what’s bad? The Stoics argue that anything that’s good – anything that’s genuinely, inherently good – will always benefit us. It will consistently benefit us (there’s the idea of consistency again). The only thing that they think falls into this category is having an excellent character or state of mind. It can be quite difficult to pin down what they mean by this because there are many aspects to it: it means being rational, consistent, mentally healthy one might say, not overcome by disruptive emotions, and possessing positive character traits such as being moderate, courageous, and fair or just. If you’ve got all these things, you will flourish in any and every situation, they suggest, no matter what life throws at you. Moreover, there’s no situation where having a calm and rational frame of mind will make things worse. Equally there are no obvious situations where being anxious, irritable, or aggressive are going to benefit you, they’d say. Having a good character is always a good thing, and never a bad thing. That’s why it is the only genuinely good thing, according to the Stoics.

So, if we want to live a good life, the most important thing we need to do is to attend to ourselves, to how we think about things (back to our judgements again) and what we think has most value. If you think that maintaining a calm frame of mind is what matters most, then like Marcus you’ll try to avoid judging that you’ve been harmed if someone speaks ill of you, because if you do judge that you’ve been harmed it will in fact be you who is harming yourself. For as we saw Epictetus say, it’s not things, but our judgements about things, that disturb us.

What about everything else? What about all the things that many of us spend much of our lives pursuing? Money, possessions, success, reputation. Are any of these things good? The Stoics are going to say ‘no’, because although sometimes they benefit us, they don’t always do so. In particular, having them won’t guarantee that we’ll live a good, happy life, as we all know from endless stories about the misery of the rich and famous in celebrity media reports. Of course, sometimes these things can be great, and not everyone who has them is miserable, but the Stoics would say that when that’s the case it’s only because the person in question has the right frame of mind. If you are psychologically in a mess, no amount of fame or fortune is going to fix that. So, if you want to be happy, rather than pursue these external things, what you need to do, they say, is attend to yourself, to your judgements, to how you think about things.

Let me paraphrase something from Seneca that nicely illustrates this thought:

When someone complained to Socrates that travelling had done him no good, Socrates replied, ‘What do you expect, you took yourself with you!’ (Seneca, Letters 28.2; see also 104.7)

We can never escape ourselves, so it is unsurprising that this is the one thing that will ultimately determine the quality of our lives. We need to attend to that before we start worrying about anything else.


Let’s now move on to the third part of Stoicism: physics. For the Stoics, physics is simply the study of Nature, the study of what exists. And this they think is the third essential part of their philosophy. There’s a lot we could say about this and some of it raises some big issues. For instance, the Stoics say that Nature is governed or organized by a rational principle which they identify with God. But this isn’t a god like the one we know from the monotheistic religions; it’s simply this rational principle, and the way we get to understand it is by studying Nature.

They also say that this organizing principle within Nature arranges things providentially, but they identify this providence with what we might call mechanistic fate, which in turn is identified with simple physical cause and effect. In short, there are multiple ways in which we might try to understand all this, not all the ancient Stoics agreed about the details, and some people drawn to Stoicism today have suggested that given all this ancient physics is inevitably outdated, we shouldn’t get too concerned about any of the details.


Even so, physics is an essential part of Stoicism and there are some basic ideas in their understanding of physics that play an important role in their philosophy as a whole. The one I’d want to focus on now is what I’ll call interconnectedness. They argue that Nature is a single organic unity, an interconnected whole. We are parts of something larger than ourselves and our wellbeing is dependent on that larger thing.

Marcus Aurelius puts it like this:

All things are woven together and the common bond is sacred, and scarcely one thing is foreign to another, for they have been arranged together in their places and together make the same cosmos. (Marcus Aurelius, Meditations 7.9)

As well as being parts of this single, unified cosmos, we are also parts of wider communities of people, both locally and ultimately as parts of the community of all humankind. We are dependent on those communities too, unless of course you happen to grow your own food, make your own clothes, and process your own sewage, but I doubt many of us do all of that. But anyone who does manage that degree of self-sufficiency from other people would, I suspect, be even more aware of their place within and dependence on Nature as a whole.

In short, none of us can survive alone. We rely on each other and on Nature, and we ought to take that into account in the choices we make. But we don’t need to choose between what’s in our interest and what’s in the interest of the community or the planet, because, ultimately, they are going to be the same. The person who acts in a selfish or anti-social way has failed to grasp this key idea of interconnectedness. The Stoics would say that such a person needs to go back and study their physics. Their moral failing is in part due to not properly understanding how the world works.

In this sense we can see not only interconnectedness among all things that exist but also the interconnectedness of Stoic philosophy itself, with physics underpinning ethics, just as we saw logic underpinning ethics earlier on. We need all three bits of the jigsaw. Anyone who has read Marcus’s Meditations will know that much of the time he is reflecting on his place in Nature. And anyone who has dipped into Epictetus will have seen him both warn against wasting time on logical puzzles while also insisting on the necessity of studying logic.

Summing Up

To sum up thus far, I think we can point to these three key ideas in Stoicism, one from each of the three parts of Stoic philosophy:

  • Logic: Judgements (determining our experience of the world)
  • Ethics: Virtue (the one thing that always benefits us)
  • Physics: Interconnectedness (we are parts of something larger than ourselves)

The Goal

Earlier I mentioned the importance of consistency for the Stoics. I talked about the virtue of being rationally or logically consistent. We might also think about ethical consistency, in both our own behaviour and in what we expect from others: ‘do unto others what you would have them do to you’, as the saying goes. If we admire someone for being trustworthy or reliable, we are in part admiring the fact that they are consistent. There’s also what we could call psychological consistency: someone who is constantly changing their mind, jumping back and forth, unable to make firm decisions or concentrate on one task at a time is unlikely to be able to live a calm and tranquil life, so we need psychological consistency too.

For the Stoics, all these types of consistency are basically one and the same. It’s all about having a consistent character that makes consistent judgements. Or to put it the other way around, it’s about making consistent judgements so that we develop the habit of thinking and behaving consistently, which is what a consistent character is.

The founder of Stoicism, Zeno, said that the goal or aim of human life is to live consistently. I think what he had in mind is the sort of mental consistency I’ve just been describing. His pupil and successor as head Stoic, Cleanthes, expanded it into living consistently with Nature, and his pupil and successor, Chrysippus, expanded it again into living consistently with our experience of what happens according to Nature. I don’t think there was any disagreement here; they were all just trying to find the best way to express the same basic underlying idea.

I think there are a number of different aspects to this:

  • To live consistently (i.e. to be rational)
  • To live consistently with Nature (in perhaps two senses):
    i) consistently with human nature (to be rational again and also to be social)
    ii) consistently with Nature as a whole (to be ecological, to work with rather than against the natural world; interconnectedness again)
  • To live consistently with what happens according to Nature (to accept what happens to us that is out of your control, to embrace fate, etc.)

This I think is what the ideal Stoic life should look like: rational, social, in harmony with the natural world, without complaint.

In order to do this, we need to i) pay attention to our judgements, ii) focus on what’s inherently good, namely having a virtuous character, and iii) understand that we are parts of a larger whole. If we can do these three things, then the Stoics think that we can live a good, calm, and happy life no matter where we are, what circumstances we find ourselves in, and what life throws at us.

John Sellars is one of the founder members (and currently Chair) of Modern Stoicism. He teaches Philosophy at Royal Holloway, University of London. He is the author of The Art of Living, Stoicism, Hellenistic Philosophy, Lessons in Stoicism, and Marcus Aurelius. He is also the editor of The Routledge Handbook of the Stoic Tradition.

8 thoughts on What is Stoicism? by John Sellars

  1. Nicole Pitthan Silveira says:

    This is one of the best explanations I have ever read. Thank you, John Sellars.
    In respect to physics, I believe the ancient Stoics would be quite fascinated by what we have discovered about our universe, especially in terms of astronomy.
    Since I started listening to Neil Tyson’s podcasts on his YouTube channel StarTalk, my View From Above exercise has changed completely.

  2. Frank Rosillo-Calle says:

    Thanks John Sellers for your excellent explanation of Stoicism. An extremely useful summary. One of the most contentious points, to me, is to differentiate Ancient from Modern Stoicism. Can we apply the same philosophy today, when so many scientific and technological advances have been made, when our morals, attitudes, etc., have changed? My view is that if ancient stoic philosophers were writing today, such writings will be very different. This does invalidate their teachings, on the contrary, but need to be updated.
    Thanks, once again, for your excellent paper.

    • Gary Thomason says:

      Very interesting point regarding an ancient and modern context. In the study of warfare – which itself is the a study of people, their wills and ways to influence those around them – we often bifurcate the context into the ‘character of war’ and the ‘nature of war’. All the science that we’ve developed as a society change the character of each war, while the essential art remains constant as the nature of war. It seems this may equally guide us in considering the essential elements of ancient Stoicism in a modern context.

  3. This is the most useful, easily digested explanation of Stoicism I’ve read. As a mature student, completing a double in psychology and philosophy, I can attest to the simplicity and clarity of the writing being rarer than hens’ teeth. Thank you, JS and GS. I will share, print, and reread. Often.

  4. James Evans says:

    Thank you Mr. Sellars for the article. As a blossoming Stoic I am find it hard to distill some idea such as Physics in a neat package. Your article has help in this quest to redefine Physics and my view. I have had revelations on the universe and dimensions through other philosophically studies. I do appreciate your thoughts on life and present moment.

  5. Ilana says:

    Thank you for this well laid out, concise, and pragmatic summary of the philosophy. I’ve bookmarked and shared this post.

  6. Julie Keyeski-Rank says:

    What about the emotions and feelings? It seems there is judgement assigned to the so-called ‘negative’ emotions, like anger, for instance. It sounds like stoicism is saying that feeling anger is a bad thing. I think that is a terrible stance to take, if in fact I am understanding that correctly. Denying and repressing our feelings is totally unhealthy. Is it not better to accept these emotions, look at them, express them in some appropriate manner, learn from them and thus grow? I am quite confused here about how not doing so is a good thing.

    • John Sellars says:

      Yes, denying or repressing emotions would be a terrible thing, but that’s not what they are proposing. As one commentator nicely put it, ‘it’s not about gritting your teeth, but about seeing things differently so that you don’t have to’. The Stoics are quite clear that anger is a bad thing – it leads to poor decisions, conflict, and sometimes violence – so the goal is not to get angry in the first place. They way one does that is by paying attention to one’s value judgements. But of course if someone does get angry, that simply has to play itself out, with the hope that they do better next time.

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