A strange thing is happening in modern philosophy: many philosophers don’t seem to believe that there is such a thing as human nature. What makes this strange is that, not only does the new attitude run counter to much of the history of philosophy, but – despite loud claims to the contrary – it also goes against the findings of modern science. This has serious consequences, ranging from the way in which we see ourselves and our place in the cosmos to what sort of philosophy of life we might adopt. Our aim here is to discuss the issue of human nature in light of contemporary biology, and then explore how the concept might impact everyday living.

The existence of something like a human nature that separates us from the rest of the animal world has often been implied, and sometimes explicitly stated, throughout the history of philosophy. Aristotle thought that the ‘proper function’ of human beings was to think rationally, from which he derived the idea that the highest life available to us is one of contemplation (ie, philosophising) – hardly unexpected from a philosopher. The Epicureans argued that it is a quintessential aspect of human nature that we are happier when we experience pleasure, and especially when we do not experience pain. Thomas Hobbes believed that we need a strong centralised government to keep us in line because our nature would otherwise lead us to live a life that he memorably characterised as ‘solitary, poor, nasty, brutish, and short’. Jean-Jacques Rousseau embedded the idea of a human nature in his conception of the ‘noble savage’. Confucius and Mencius thought that human nature is essentially good, while Hsün Tzu considered it essentially evil.

The keyword here is, of course, ‘essentially’. One of the obvious exceptions to this trend was John Locke, who described the human mind as a ‘tabula rasa’ (blank slate), but his take has been rejected by modern science. As one group of cognitive scientists describes it in From Mating to Mentality (2003), our mind is more like a colouring book, or a ‘graffiti-filled wall of a New York subway station’ than a blank slate.

In contrast, many contemporary philosophers, both of the so-called analytic and continental traditions, seem largely to have rejected the very idea of human nature. A prominent example is our colleague Jesse Prinz at the City University of New York, who argues forcefully for what is referred to as a ‘nurturist’ (as opposed to a ‘naturist’) position in his book Beyond Human Nature: How Culture and Experience Shape the Human Mind (2012). More recently, Ronnie de Sousa argued that modern science shows that human nature does not exist and, drawing on Jean-Paul Sartre’s notion of radical freedom, concluded that this favours an existentialist philosophical outlook. We beg to differ.

What exactly does science tell us about the idea of a human nature? If we take evolutionary biology seriously, then we certainly should reject any essentialist conception of it, such as Aristotle’s. There is no immutable, clearly defined ‘essence’ that characterises human beings, and only them, within the whole animal world. From Charles Darwin onward, the scientific consensus has been pretty clear: we are but one species among millions on Earth, members of a not particularly numerous branch of the tree of life, endowed with unusually large and structurally complex brains. Our particular lineage gave origin to the species Homo sapiens at least 300,000 years ago, resulting from a long evolutionary period, which unfolded over millions of years from the point of divergence from our most recent common ancestor with the chimpanzees, our closest phylogenetic cousins.

Put that way, it would seem that biology does indeed do away with any idea of human nature: whatever characteristics our species possesses are the result of a continuous process of evolutionary differentiation from other species of primates, and there is no reason to believe that such process is over, or will be any time soon. Moreover, people are fond of citing the famous figure that humans and chimpanzees differ ‘only’ in about 1-2 per cent of their genomic sequence, implying that we are not really as special as we’d like to think.

But as Kevin Laland has pointed out in his book Darwin’s Unfinished Symphony: How Culture Made the Human Mind (2017), that small percentage translates into thousands of structural changes at the genetic level, which in turn can be combined to yield millions of ways in which humans are distinct from chimpanzees. Just because the difference is small in percentage, it doesn’t mean it is not both very obvious and highly consequential.

In light of this, we think that the picture emerging from evolutionary and developmental biology is – contrary to the widespread opinion among contemporary philosophers – one that very much supports the notion of human nature, just not an essentialist one. Human nature is best conceived of as a cluster of homeostatic properties, ie of traits that are dynamically changing and yet sufficiently stable over evolutionary time to be statistically clearly recognisable. These properties include characteristics that are either unique to the human species, or so quantitatively distinct from anything similar found in other animals that our version is unquestionably and solely human.

Take language, for instance. Plenty of other animals (and even plants and bacteria) communicate, meaning that they exchange signals aimed at improving their own or their kin’s survival. But no other living species has anything even remotely like human language, with its complex grammar and high levels of recursion (where a linguistic rule can be applied to the results of the application of the very same rule, and so on). Other animals, such as octopuses, have large, complex brains and nervous systems, but no other animal has both the size (relative to the body) and especially the structural asymmetry and layering of the human brain; for instance, its enormously developed frontal cortex, which is in charge of reward, attention, short-term memory tasks, planning and motivation.

The list could go on and on, but the basic point is that it is fallacious to state that there are no fundamental differences between humans and other animals just because the boundaries are fuzzy and dynamic (over evolutionary time). As Justice Potter Stewart said, in a case about pornography versus art in 1964: ‘I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description; and perhaps I could never succeed in intelligibly doing so. But I know it when I see it.’ A modern biologist and a scientifically informed philosopher could say something very much along the same lines about human nature. We all know it when we see it.

Now, if human nature is real, what are the consequences from a philosophical perspective? Why should a philosopher, or anyone interested in using philosophy as a guide to life, care about this otherwise technical debate? Let’s explore the point by way of a brief discussion of two philosophies that provide particularly strong defences of human nature and that are aligned with cognitive science: existentialism and Stoicism.

The temptation to link existentialism with the idea of a tabula rasa is understandable. At the heart of existentialism is Jean-Paul Sartre’s idea that ‘existence precedes essence’, meaning that we didn’t choose to be born, but we’re free to figure out what to do about it. Sartre took this very seriously, speaking of freedom as a lack – or a gap – at the heart of consciousness, and claiming that we’re free even when in chains. In one of his more radical statements, he wrote: ‘Never were we freer than under the German occupation. We had lost all our rights, and first of all our right to speak. They insulted us to our faces … They deported us en masse … And because of all this we were free.’ It is perhaps not surprising that Sartre is frequently mocked for overstating the extent to which we are free.

Even Simone de Beauvoir thought he took it too far, particularly when he told her that her seasickness was all in her head. In her autobiography The Prime of Life (1960), she wrote: ‘If you gave way to tears or nerves or seasickness, [Sartre] said, you were simply being weak. I, on the other hand, claimed that stomach and tear ducts, indeed the head itself, were all subject to irresistible forces on occasion.’

Although de Beauvoir also accepted that existence precedes essence, she was more attuned than Sartre to the ways in which our ‘facticity’ – the facts of our existence – influence our lives. For example, we can’t choose our bodies or the economic and social situations in which we find ourselves, and often we see other people as the immutable banes of our existence. De Beauvoir argues that although we’re not free from our natural condition, it doesn’t define our essence, which is how we create ourselves out of our facticity. We don’t live only to propagate the species as animals do; rather, we are beings who look for meaning in our lives, and we do it by taking risks to overcome ourselves and our situations. This is human nature: perpetually seeking to escape our natural condition, to transcend – surpassing the given – towards self-chosen, concrete goals. But this isn’t at all easy, and is one of the reasons why anxiety is a fundamental theme of existentialism. To be human is to live in ambiguity because we are forever caught in a tension between the facts of our lives and the will to overcome them.

Biology might seem to offer a simple explanation for some limitations. For example, consider the old-school argument that women are ‘naturally’ suited for caregiving roles. This is both a wrong and a harmful way to think about our nature. It’s wrong because, as de Beauvoir points out in The Second Sex (1949), gestating babies is a biological female function, but rearing children is a social commitment. And it’s harmful because the assumption that biology sets our destiny is oppressive. Historically, women have been defined primarily by the same biological functions they share with other animals, tethered in myths about femininity, and robbed of the opportunity to transcend.

Natural obstacles provide a different sort of limitation. It might be absurd for de Beauvoir to persist with sailing if she vomits constantly, but giving up on her goals because of seasickness is stupid, too. Sometimes, we don’t have the power to break our chains, and we fail in our projects, but resignation is not the answer. To transcend is to recognise our resistances and failures, and to rebel against them creatively. This perspective matters because it emphasises that, while there are fixed elements to our being, we are not fixed beings, since we are (or ought to be) free to choose our projects. Neither biology nor natural obstacles limit our futures to a great extent, and how we live out our human nature will vary because we give different meanings to our facticities. An authentic life is about acknowledging these differences, and stretching ourselves into an open future. It does not follow that this openness is unlimited or unconstrained. We are limited, but mostly by our own imagination.

For the Stoics, human nature circumscribes what humans can do, and what they are inclined to do

An interesting contrast here is provided by a philosophy that is in some respects very different, and yet shares surprising similarities, with existentialism: ancient Greco-Roman Stoicism, which has seen a remarkable revival in recent years. The Stoics thought that there are two aspects of human nature that should be taken as defining what it means to live a good life: we are highly social, and we are capable of reason. Therefore, to ‘live according to nature’, as they advised us to do, means to apply reason to the improvement of the human polis. In turn, the way to accomplish the latter is to improve one’s judgment (the faculty of prohairesis, which distinguishes us from any other animal species), and to exercise the four cardinal virtues of practical wisdom, courage, justice and temperance.

At first glance, it might seem that human nature plays a far more crucial role in Stoicism than in existentialism. Indeed, it is tempting to accuse the Stoics of committing an elementary fallacy, to argue for a particular way of life by appeal to nature. But Seneca, Epictetus and co were excellent logicians, which should make us pause before dismissing their philosophy so quickly. On closer examination, it is clear that for the Stoics, human nature played a similar role to that played by the concept of facticity for the existentialists: it circumscribes what human beings can do, as well as what they are inclined to do. But the parameters imposed by our nature are rather broad, and the Stoics agreed with the existentialists that a worthwhile human life can be lived by following many different paths.

Indeed, Stoic literature even features a story similar to the debate between de Beauvoir and Sartre on seasickness. It is told by the Latin author Aulus Gellius, who writes about a Stoic philosopher experiencing a severe storm while on a ship. Gellius noticed how the philosopher became pale and trembled in the midst of the storm. Once things had calmed down, he asked the philosopher how come his Stoicism had not prepared him better to withstand those frightening moments. His response is illuminating:

When some terrifying sound occurs, either from the sky or from the collapse of a building or as the sudden herald of some danger, even the wise person’s mind necessarily responds, and is contracted and grows pale for a little while, not because he opines that something evil is at hand, but by certain rapid and unplanned movements antecedent to the office of intellect and reason. Shortly, however, the wise person in that situation ‘withholds assent’ from those terrifying mental impressions; he spurns and rejects them and does not think that there is anything in them which he should fear.

In other words, just as de Beauvoir explained to Sartre, the ‘facticity’ of our biology is here to stay, but we have a choice about how to regard it and manage it. And that’s what philosophy teaches us.

The Stoics grounded that teaching in an approach most famously associated with Epictetus, the 2nd-century slave-turned-teacher who became one of the best-known philosophers of antiquity. He developed a whole ethics based on the idea that we play a multiplicity of roles in life: some of them are given (we are all human beings, sons or daughters of our parents, and so forth), and some are chosen (our careers, whether we wish to have children and become parents or not).

How we play these roles is up to us. In Book I of the Discourses, Epictetus discusses the case of two slaves who react differently to the same demeaning situation (having to hold their master’s chamber pot while he’s relieving himself). What determines the difference is how the slaves see themselves as human beings, a concept not that different from the existentialist notion of authenticity. Epictetus concludes the analysis of that example by admonishing his students in a way that Sartre and de Beauvoir might have approved of: ‘Consider at what price you sell your integrity; but please, for God’s sake, don’t sell it cheap.’

It’s not only modern science that tells us that there is such thing as human nature, and it’s no coincidence that a number of popular modern therapies such as logotherapy, rational emotive behaviour therapy and cognitive behavioural therapy draw on ideas from both existentialism and Stoicism. No philosophy of life – not just existentialism or Stoicism – could possibly exist without it.

If we were truly tabulae rasae, why would we prefer certain things to others? What could possibly urge us to seek meaning, to build relationships with other people, to strive to improve ourselves and the world we live in? We do all that because we are a particular kind of intelligent social animal, just as the Stoics thought. And we do it within the broad constraints imposed by our (biological as well as contingent) facticity, as the existentialists maintained. There is no single path to a flourishing human life, but there are also many really bad ones. The choice is ours, within the limits imposed by human nature.