Human beings are highly complex organisms that have shown a remarkable ability, in different times and places, to create very different ways of social life. Theories of human nature are, mostly, social and political constructs that forget that history. Different ideologies each present a different theory of human nature that supports its agenda: for example, the family of liberal ideologies (libertarianism and classical and welfare liberalism) believes in homo economicus, the idea that human nature is self-interested and competitive, and this it defines as "rational." Communist theory maintains an idea of man-the-maker, sometimes called homo faber, which defines humans as laboring beings who creatively transform nature to meet their needs. (These are hardly the only examples: Nazis and fascists have had their own views of what it meant to be or not be human, while today's conservatives usually conjoin homo economicus with the idea that humans are fundamentally flawed and/or sinful.) These partial views of human nature have negative consequences. The neoliberal view of homo economicus has promoted a selfish, narcissistic culture in advanced capitalist societies and the United States in particular. Communism’s view of homo faber arguably overemphasized human cooperation and creativity and, by neglecting human domineering capacities, failed to prevent totalitarianism in its name.
Thus theories of human nature, in a supreme act of cherry-picking the evidence, single out one, or at most a few, aspects of the human organism’s highly complex biology and psychology, emphasize them over the rest, and declare them to be the core part of our being. Other human traits get shoved to the side and conveniently ignored, or are put into the categories of the undesirable, the abnormal, the less-than-human – when in fact they too are natural human qualities and a natural part of the human experience. "Reason" historically was elevated this way in the western canon, with emotion marginalized as irrational, and while this has been slowly changing this binary is still widespread. Yet emotions are arguably more central to the human experience than cold reason is, and reason itself is proving to be an embodied, mostly subconscious, and highly emotional aspect of human functioning. Reason itself is not definitive of being human, it is only part of the picture.
It can be easy to fall into the trap of thinking that science tells us what human nature is, or will someday, once it has a more complete understanding of our physiology. But this mistakes the kind of construct that a statement about human "nature" is. A claim about human nature is a speech act that asserts that some aspect of the human organism is the core of humanity, defining what it means to be human. (Even if a speaker means it differently, a claim about human nature will normally be understood by the audience in this way. We do not determine our definitions alone.) And indeed some neuroscientists and practitioners of evolutionary psychology, overwhelmed in recent decades by the non-positivist epistemologies of social constructivism and postmodernism, are desperately seeking a core essence or nature of humanity as a fundamental foundation. They have faith that science will be able to give humanity a universal morality one it has discovered what human nature is, a project that I think is likely to be a horrific failure, as the history of eugenics, which was once considered a legitimate science, warns us.
Yet while science can tell us many things about the functioning of the human respiratory system, the digestive system, even the nervous system and the brain, none of this tells us what “human nature” is, as that concept has been conventionally understood to mean. Oh, science helps us understand our anatomy, to be sure, and helps to tell us what many of the physical limits of our bodies are: human beings can’t fly or breathe water unaided, for example (although many such facts were known before the scientific method arrived on the scene). But science has yet to empirically prove that a core human “nature” exists, and is unlikely to be able to do so. Science can tell us about our physical, biological systems and how they operate. But that cannot determine for us which of those systems should be definitive or are the “core.” These are deliberative, even moral, choices that people make about the qualities they value in human beings; these choices must be decided by them, and can’t be discovered in a lab.
And science doesn’t do any better if it tries to step back from the various parts of the human organism and examine the whole in order to define human nature – the standard method of the natural sciences, reductionism, or breaking things down into their component parts to examine their inner workings, is ill suited to such an enterprise. Science can tell us many things about the functioning of the brain, at least at the level of its parts and how they interact. And this does tell us some things about the mind that the brain helps to produce. Science can even tell us a great deal about human psychology, or at least our psychology as it exists in this historical era and in this kind of society. But natural science's analytical, reductive approach doesn't work well to give us a complete picture of the brain and mind, because brain and mind themselves are parts that develop and become complex only as parts of a greater social and cultural whole. (Social science does a little better, but it really takes philosophy to do this). The brain/mind is made up of atoms and molecules and neurons, of course, but it becomes a fully functioning organ only when it develops and grows due to sensory stimulation from its environment. And that environment, for human beings, has long been a social one. I said a moment ago that the brain “helps” to produce the mind, and that choice of words was conscious, because mind doesn’t emerge without a social context, too. Neural pathways are set during childhood development, and to some degree throughout life, by the social experiences that human beings have. The older term for this is “learning,” and it helps demonstrate that Aristotle was on to something when he said to be human was to be a zoon politikon – a political or social animal. Just as birds fly in flocks and lions hunt in prides, humans form societies, and these societies fold back and also form the humans which make them up. Because the brain develops socially through learning it is more flexible than many scientists, or ideologists, want it to be. We can’t be literally anything, of course – we don’t have wings to fly or gills to breathe – but in terms of how we arrange our social organizations we are far more flexible than either natural science or political powers usually want to admit.
We even create societies that are capable of physically overcoming our biological limitations through the social production of knowledge and engineering – as with the development of the airfoil to fly and scuba tanks to dive deep into the seas. Not only have we reached the point where we can directly influence our own evolutionary development and thus alter our “nature,” there is another way in which the social has long been more efficacious than human nature: not all change in the world is evolutionary, and the most important changes underway now throughout the biosphere are a result of human society and all it has developed. Climate change, habitat reduction, and industrialization have all increased the rate of extinction, and some human-caused disasters such as worst-case climate change or nuclear war could potentially completely overwhelm evolutionary adaptation and either wipe out all life on Earth or lead to a new geological era through massive extinctions.
Human nature is often felt to be morally constraining, in that if something is thought to accord with that nature it is thought to be good, while something that goes against that nature is thought to be bad or wrong. But because any idea we have of human nature is a social and political construct specific to a time and place – including whatever idea of human nature you hold in your head right now – the concept of “nature” loses this regulatory quality. We simply cannot base morality on it and have to find other reasons to be moral.
Theories of human nature present us with one-sided views of the highly complex, adaptable, and changeable organisms known as "human beings." But these partial views of human “nature" are limited stories: we have never gotten the complete picture, and it is doubtful that we ever will. We ought to give up the project of finding a core moral defining feature; not only is it a conceptual dead end, doing so undercuts many authoritarian impulses and breeds tolerance, and furthermore frees us up to become more adaptable as we face changing world circumstances. The best we can say about our nature, it seems to me, is to loosely say we are very complex organisms with a variety of bodily traits, features, and limitations, that we develop, learn, and adapt together socially with other members of our species, and that we have a history of creating many different ways of life in response to our circumstances. We should stop trying to single out one aspect of our complex entities, such as rationality or self-interest, and impose it on everybody or set it as a standard to which all must aspire. Even scientists should be cautious and focus on telling us how the parts work, rather than engage in a quixotic quest for a core human nature.