How to be an Aristotelian

John Sellars

Let me start with a wild claim that may strike you as outrageous hyperbole: Aristotle is not merely the most important ancient philosopher, and not merely the most important philosopher of all time; Aristotle is the single most important human being ever to have lived.

On what grounds can I make such a grand claim? Well, let us think about what it would mean to be the single most important human being ever to have lived. Who would be a plausible candidate? It would have to be someone whose ideas have impacted on the lives of millions of people over a vast period of time – over centuries, if not millennia. There couldn’t be many serious candidates.

Bust of Aristotle, Roman copy after a Greek bronze original by Lysippus of 330 BC (National Roman Museum, Palazzo Altemps, Rome, Italy).

How about Jesus? Was he a man though? Or God? Or both? We are already embroiled in complex theological questions. What about Muhammad? He was definitely a man, and peace be upon him, but there’s a sense in which he didn’t have anything of his own to teach, for he was a prophet, communicating the word of God. Then there’s the Buddha, a human being and one with lots to teach. His ideas had a huge impact right across Asia for centuries, as well as, more recently, in the West. Another serious candidate might be Confucius. He is without a doubt a thinker of great stature, but his influence has been largely confined to China and primarily in the domains of ethics and politics.

Are there any other serious contenders? You already know what my answer is going to be.

More than anyone else, it is Aristotle (384–322 BC) who has shaped the way that we think about so many things. His ideas and concepts have seeped into our natural ways of thinking to the point of becoming imperceptible. His work studying animals on the island of Lesbos and elsewhere in effect created the discipline of biology and – along with his wider reflections about the nature of knowledge – laid the foundations for all empirical science. He was also the first person to study the structures of rational thought, inventing formal logic in the process, and clearly articulating for the first time key logical principles, such as the Law of the Excluded Middle: any proposition can only be either true or false. That binary division is the foundational idea that stands behind the digital world that we increasingly inhabit.

The Aristotelian Constitution of the Athenians, written in the late 4th century BC (papyrus copy of c. AD 100, now preserved in the British Library, London).

His study of different types of political organization and his fieldwork gathering the constitutions of existing political states around the ancient Mediterranean laid the foundations for the discipline of political science and, arguably, social science in general. His analysis of Greek drama set out the core elements for a good story, inventing literary criticism in the process, and his analysis continues to be used today by Hollywood script writers.

So, the next time you sit down to watch a movie, perhaps streamed over a digital service, reassured that you have been protected by the latest vaccines developed by life scientists, take a moment to reflect that, although he certainly can’t take credit for all this, it was nevertheless Aristotle, just one man, who took the first steps down multiple paths to lead us to where we are today. Aristotle: the single most influential human being ever to have lived. His ideas have shaped the lives of millions over centuries in countless ways.

Aristotle teaching a student, illustration from a 13th-century Mesopotamian copy of the Kitāb naʿt al-hayawān, a bestiary attributed to Jabril ibn Bukhtishu (British Library London MS or. 2784, f.96r, c.1220).

However, making this grand claim does not mean that I agree with Aristotle on everything, or even anything. Indeed, I’m not convinced that Aristotle agreed with himself on everything that he said. I certainly do not think that he would have wanted us to accept his ideas as a dogmatic body of knowledge to be venerated. Many of the claims that he makes are provisional, tentative proposals, open to criticism and subject to rejection should new evidence appear. He sometimes approaches the same problem more than once, giving seemingly conflicting answers. All this underlines the fact that he certainly wasn’t a dogmatic thinker and that his works don’t necessarily form a comprehensive monolithic system, even though it is quite easy to see them that way.

Aristotle wasn’t a rigid system builder; he was an inquirer, a man in pursuit of knowledge, restlessly in search of answers to every conceivable question. Indeed, one of his translators has commented in frustration at his “excessive tentativeness or caution”, noting how often in his works Aristotle uses the word “perhaps”.[1] In his studies of animals, Aristotle is quite explicit about this: every theory is open to refutation by further observation, he says. Nor was he enamoured of the idea of intellectual authority figures, famously commenting that, although he was a friend of his teacher Plato, he was a greater friend of the truth.[2] He put forward ideas that he thought were true – or at least the most plausible – based on observation and argument, but it is difficult to imagine that he would have expected anyone to believe anything he said simply because he had said it.

The School of Aristotle, Gustav Adolph Spangenberg, 1888 (fresco in the Martin-Luther University of Halle-Wittenberg, Germany).

The one thing Aristotle was emphatic about, though, was the importance of doing philosophy. According to him, we are rational animals, which is to say that we are animals, but we differ from other animals in having the power of reason. That’s our defining characteristic. It’s what makes us who we are. It is what he calls our function (ἔργον, ergon). Aristotle thinks that many things have functions and that those things are only really what they are in the fullest sense when that function is being used. To use an example that Aristotle himself quite liked, eyes are for the sake of seeing; that is their function. If someone had eyes but never opened them, the capacity of sight would never be used – in his terminology, their potential for seeing would never be actualized. Insofar as their very existence as eyes is defined in terms of their function, the ability to see, there is a sense in which eyes that never get the opportunity to see fail to be eyes in the fullest sense.

The same applies to a human being who fails to use their capacity for reason. In order fully to be a human at all, one must do philosophy, Aristotle argues:

The function of the soul, either alone or most of all, is thinking and reasoning. Therefore it is now simple and easy for anyone to reach the conclusion that he who thinks correctly is more alive, and he who most attains truth lives most, and this is the one who is wise… Thus we attribute living more to the one who is awake rather than to the one who is asleep, to the one who is wise more than to the one who is foolish.[3]

Aristotle, Justus van Gent, c.1476 (Musée du Louvre, Paris, France).

In the case of sight, being able to see obviously brings with it a wide range of practical benefits, such as not bumping into things; it enables us to do many things. Aristotle comments that the same applies to philosophical thinking – it can be practically beneficial in a variety of ways, but in both cases the benefits are merely welcome by-products. Even if someone gained no practical benefit from seeing, they would still prefer to be able to see than not, he comments, and the same applies to philosophical thinking. We do it for its own sake, but it also benefits us in various ways.

Despite this focus on the intrinsic importance – indeed, the necessity – of philosophy as an activity, Aristotle also stresses that it is only through philosophy that it will be possible for us to live a happy life. It’s only by doing the one thing that defines us as human beings that we’ll really flourish and live well.

I think it’s worth saying that he doesn’t think we ought to do philosophy because it will make us happy. He doesn’t hold the sort of view that later Stoics and Epicureans seem to express, that we ought to do philosophy in order to live a good life. I think his view is that we ought to do it simply to be human beings in the fullest sense. But at the same time he thinks that it will bring us happiness and that nothing else can.

The beginning of Book 6 of Aristotle’s Nicomachean Ethics in a 15th-century manuscript commissioned by Andrea Matteo Acquaviva, Duke of Atri (Austrian National Library, Vienna, Cod. phil. gr. 4, fol. 45v.).

In the light of all this, we might ask the question “What does it mean to be an Aristotelian?” I think that we can draw a clear distinction between two different ways in which we can use the word “Aristotelian”. The first sense includes what we might call ‘dogmatic Aristotelianism’. This often assumes that Aristotle left behind a single, systematic body of thought and that to be an Aristotelian means to subscribe to the truthfulness of this system, slavishly following the letter of Aristotle’s texts. There have certainly been plenty of dogmatic Aristotelians through the ages. Aristotle himself, though, certainly wasn’t a dogmatic Aristotelian in this sense. As I’ve already said, Aristotle was committed to a life of inquiry, a life of continual investigation and observation in the pursuit of knowledge.

It is this idea of open-minded and endlessly curious inquiry that can give us what I think is a second, and much better, sense of what it means to be an Aristotelian. This is simply to be a human being in the fullest possible way. It doesn’t require us to accept anything that Aristotle said as true – indeed, a good deal of what he thought is now obviously false (especially in his cosmology and biology); instead, it simply involves joining him in the ongoing process of trying to understand the world in which we live.

Aristotle discusses medicine with two students, illustration from Évrard de Conty’s French translation of the Pseudo-Aristotelian Latin treatise Problemata Physica (Problems of Nature), 1450-75 (National Library of the Netherlands, The Hague, KB 133 A 3 f.1r).

There is an old narrative that claims that the development of modern science in the 16th and 17th centuries involved – indeed, required – a complete break from the existing Aristotelian tradition. Aristotle had become such an overwhelming figure of intellectual authority that his shadow was stifling progress. As Francis Bacon (1561–1626) put it, “knowledge derived from Aristotle, and exempted from the liberty of examination, will not rise again higher than the knowledge of Aristotle.”[4] In truth, the situation was more complex than this narrative of wholesale rejection implies. A number of thinkers in the 16th century were all too aware from their own close study of Aristotle’s texts that he was a champion of observation and open inquiry. The problem was not with Aristotle himself but with the way that some of his followers read him.

The Italian philosopher Jacopo Zabarella (1533–89) drew a distinction between the interpreter of Aristotle who is focused narrowly on what Aristotle wrote and the true Aristotelian who embraced his spirit of inquiry. It was a distinction between a focus on doctrine or method, on the letter or the spirit of Aristotle’s works. Around the same time, another Italian philosopher, Alessandro Piccolomini (1508–79), commented that in order to be a faithful Aristotelian he would rely first and foremost on experience and observation, even if that meant disagreeing with Aristotle from time to time. In order “to better imitate Aristotle”, he wrote, “I will leave Aristotle… each time the senses show me the opposite to be true.”[5]

A particularly interesting example of this way of thinking can be found in Galileo Galilei (1564–1642). In Galileo’s famous Dialogue Concerning the Two Chief World Systems (1632), he mocked the Aristotelians of his day for their slavish devotion to the letter of Aristotle’s works, regardless of what new evidence might be presented to them. Yet along the way Galileo commented that “if Aristotle were now alive, he would change his opinion.”[6] Galileo was happy to describe himself as an Aristotelian in Piccolomini’s sense of the term, free to depart from Aristotle’s views whenever the evidence demanded. He could see that the new 16th-century focus on observation and experimentation was in many ways thoroughly Aristotelian in spirit. Aristotle himself would surely have hated the idea that his works had become authoritative sources of rigid doctrine that were impeding the development of science.

Galileo and his assistant Viviani (during Galileo’s house arrest), Tito Lessi, 1892 (Museo Galileo, Florence, Italy).

So, how to be an Aristotelian? In the light of what I’ve been saying, to be an Aristotelian doesn’t mean subscribing to a certain set of ideas, although it is certainly possible to be an Aristotelian in that narrower sense too. What I want to suggest is that to be an Aristotelian is simply to join Aristotle on his endless quest for knowledge. It simply means to do philosophy. As he famously put it in the opening line of his Metaphysics, “all human beings by nature desire to know.” Philosophy, he said, is the product of wonder generated by our encounter with the world around us.

Whenever we start to think about those big questions about the nature of the world, ourselves, and our place in it, we start to do philosophy and that is what being an Aristotelian is all about. Indeed, Aristotle himself argued that that’s simply what it means to be a human being, exercising our capacity for reason and understanding. So, in a sense, we are all Aristotelians, whether we like it or not. We can’t escape him, just as we can’t escape his influence. He’s the single most important human being ever to have lived.

John Sellars is Reader in Philosophy at Royal Holloway, University of London. His recent books include Lessons in Stoicism (Penguin, 2019), The Fourfold Remedy (Penguin, 2020), and now Aristotle (Penguin, 2023). He has previously written for Antigone about the Stoic Roman emperor Marcus Aurelius.


1 Richard Robinson, Aristotle’s Politics Books III and IV (Oxford UP, 1962) viii.
2 Nicomachean Ethics 1096a11–15, the thrust of which is traditionally given as the Latin maxim Amicus Plato, sed magis amica veritas (“Plato’s a friend, but a greater friend is truth”).
3 Protrepticus fr. 14, trans. D.S. Hutchinson & M.R. Johnson in “Authenticating Aristotle’s Protrepticus,” Oxford Studies in Ancient Philosophy 29 (2005) 193–294, at 266–7.
4 The Advancement of Learning 1.4.12, W.A. Wright ed. (Oxford: UP, 1963) 37.
5 Quoted in Marco Sgarbi, “What does a Renaissance Aristotelian look like? From Petrarch to Galilei,” in HOPOS: The Journal of the International Society for the History of Philosophy of Science 7 (2017) 226–45, at 237.
6 Quoted in Sgarbi (ibid.) 240.