Everyone must have noticed that human nature is currently a hot topic. The old Delphic injunction "know thyself" now guides a great deal of scientific activity, as well as work in the traditional humanities. This is surely admirable, for there are no trade union barriers in the pursuit of knowledge. It must be a good thing if ³ÉÈËVRÊÓƵr and Augustine, Shakespeare and Hobbes, Hume and Proust are joined by biologists, cognitive scientists, game theorists, evolutionary psychologists, social psychologists, pharmacologists, endocrinologists, zoologists, economists, robotics engineers, quantum theorists and, without doubt, others I have failed to mention and to whom I hereby apologise.

I am a good ecumenicist, or magpie. I think we philosophers need to profit from as much knowledge as we can absorb, from all kinds of sources. Unfortunately, I am not sure that this eclectic attitude is always reciprocated.

The different sciences go about things in different ways, but their practitioners often seem joined in confidence that their tools and procedures have made philosophical reflection obsolete. The philosophical armchair is as discredited an aide to reflection on human nature as the omphalos at Delphi. Indeed, many younger philosophers themselves dispose of such an embarrassing old piece of lumber and talk knowingly only of hippocampi, frontotemporal lobes, oxytocin and evolutionarily stable strategies.

By human nature, of course, I mean not our nature as it is discovered by the camera or in the anatomy lesson, but our nature as it is discovered in our doings. It is the ways in which we think and feel that intrigue us, and it is the old distinction between the Geisteswissenschaften and Naturwissenschaften that is being eroded by the colonial advances of the latter.

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Not that this piece of colonial history has in the past been much more glorious than others. There was not only science's flirtations with such things as eugenics, but also the rather alarming tendency for distinguished scientists entering new territories to present not distinguished science but rather - dare one say it - armchair speculation, or ideology, in its place.

Biologists, for instance, have found it irresistible to read the Darwinian struggle into everything we care about. "What passes for cooperation turns out to be a mixture of opportunism and exploitation," says distinguished American biologist Michael Ghiselin. "Scratch an altruist, and watch a hypocrite bleed." Any other view is mere sentimentalism.

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Richard Dawkins once veered away from this bleak vision only by having us "rebel against the tyranny of the selfish genes". But this seemed to make sense only if, like some religious people, Dawkins thought that the human soul or spirit floats beautifully free of mere physical processes and, with resources drawn from God knows where, can stick its ghostly finger in and alter the course that these would otherwise have taken.

The truth is that the theory of evolution by natural selection does not need this ethereal help, since it is itself silent about which psychologies will have proved adaptive in whichever natural and social settings led up to the present time. So Ghiselin's announcement of a war of all against all is as innocent of the data as an announcement that people only want sex in ways that maximise their chance of propelling their genes into the next generation and remain chaste when this cannot be achieved. It is also notoriously untrue to Darwin himself.

We armchair types may also want to wonder whether "human nature" is itself a respectable concept, or merely a remnant of the Aristotelian idea that everything has a "natural state". There is variation in the human genome - indeed, most scientists believe that fomenting this variation is the function of sexual reproduction and its accompanying genetic recombinations. And then the journey from genome to proteins to brains to psychology is highly variable, as genes express themselves differently in different environments. For most purposes, the old opposition between nature and nurture is spurious: genes need environments and environments need genes if a human being is to emerge. With different cultural environments you get different human natures, although of course you can always argue about just how deep the differences are.

One strategy to see what our psychologies are like deep down is by speculating on the supposed environment of the Pleistocene, as if that shows us human nature in the raw, with the rest the relatively superficial work of culture. But perhaps there is no raw to be found. Anything raw was just one more environment, and any behaviour we suppose to have taken place in that environment may be a poor guide to what we find around us in ours. After all, nobody could have predicted our recent ability to read and write, given our vast millennia of complete illiteracy.

Delving into the doings of the brain is currently an even more popular road to self-understanding than evolutionary speculations. Caution here might first point out that brain events are interpretable in psychological terms only by first being calibrated against the unmistakable manifestation of psychological events, which are people's sayings and doings. Yet the idea that we will get a new line on what we think and feel through functional magnetic resonance imaging (fMRI) scans and the rest is unlikely to be derailed by such epistemological quibbles.

In her brilliant book Delusions of Gender: The Real Science behind Sex Differences (2010), Cordelia Fine quotes work showing that people find essentially vacuous non-explanations of such alleged things as gender difference much more compelling when they are gilded with neuroscience. So while most people realise that "women are worse at spatial reasoning because women are worse at spatial reasoning" is a non-explanation, they are much more impressed by "brain scans of the right premotor area, known to be involved in spatial-relational tasks, indicate that women's poor performance relative to men's causes different types of brain responses. This explains the gender difference in spatial-reasoning abilities." Yet this just repeats the same non-explanation, only larded with the predictable fact that a bit of the brain is involved.

Neuroscience has not only influenced descriptions of what we are like, but also injunctions as to what we ought to be like - ethics. So while consequentialist, or cost-benefit, thinking requires calculations, judgements made because we shrink from some course of action may be relatively more emotional.

Asked to contemplate whether to divert a trolley from a course on which it will kill five people on to a sidetrack where it will kill one, many people just think of the numbers and say that they would. Asked to contemplate pushing an unfortunate fat man off a bridge in front of the same trolley, stopping it and preventing it from killing the five, more people say they would not.

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And sure enough, the first case is associated with more activity in the dorsolateral prefrontal cortex, the latter with more activity in emotional centres such as the ventromedial prefrontal cortex. Does this show us anything new about how we should think of such cases? Some have argued that it does, on the grounds that cognition and reasoning are to be preferred to snap emotional reactions. It is even suggested that this is an argument for generally consequentialist moral reasonings, as opposed to "deontological" reactions associated with ideas of what is permissible or obligatory.

That at least seems a rather wild extrapolation, since not all deontological reasonings have the same emotional colour. It's quite reassuring that people lying in scanners get a frisson of horror at the idea of hurling each other in front of large vehicles, but it is not so clear what the frisson has to do with the judgement that one should not do it.

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Varying the example, suppose I feel I ought to invite you to my party because you once looked after my cat. I am then reasoning deontologically, not in terms of the likely consequences of inviting you. But I doubt very much that I would get hot under the collar or break out in a cold sweat if I think that way (although I might if I dwell on the possible consequences of inviting you, supposing they are lurid enough). All this shows is that one can make many ordinary judgements in a clinically detached, or highly emotional, state of mind. But whether the judgements are reasonable or wild may vary quite independently of that.

Perhaps it is too late for quibbling or wallowing in nostalgia for the philosophical armchair. When Edge, the forward-looking, up-to-the-minute, state-of-the-art web forum for the cr¨¨me de la cr¨¨me of academia, recently decided to sum up where we are now in understanding morality, it invited four psychologists, two neurologists and but one philosopher (incidentally, all males). They issued their communique under eight banner headlines, as follows:

? Morality is a natural phenomenon and a cultural phenomenon

? Many of its building blocks are innate

? Moral judgements are often made intuitively, with little deliberation or conscious weighing of alternatives

? Conscious moral reasoning plays multiple roles in our moral lives

? Moral judgements and values are often at odds with actual behaviour

? Many areas of the brain are recruited for moral cognition, yet there is no "moral centre" in the brain

? Morality varies across individuals and cultures

? Moral systems support human flourishing, to various degrees.

Well, there we have it. Hide your faces, Plato, Hobbes, Hume, Nietzsche, Rawls and the fuddy-duddies who still read them. True enough, by turning their pages, one might have found precursors of seven out of the eight revelations - only the sixth seems near to being news, although I would like to have been told who or what does the recruiting. And given that moral thinking often involves empirical data, ingrained habits, empathy, prediction, imagination, calculation and inference, I did find myself wondering whoever supposed that there would be a "moral centre", whatever that might be, anywhere at all.

Still, that apart, I thought it showed admirable scientific caution that the panel stopped at these eight headlines. An armchair speculator might have been tempted to go on, at least up to 10. "Moral issues sometimes make people annoyed" or "It's sometimes hard to get moral agreement" might have added to the bouquet, without making it look or smell markedly more faded than it already does. Alas, more research is needed, since I have no evidence from either web questionnaires or fMRI scans for either of these assertions.

But as I say, I am a magpie, and there are nice titbits to pick up everywhere we look. So psychologists have found that if you are reduced to begging, it is better to make your pitch outside a bakery, where the appetising smells please passers-by, than outside somewhere neutral, let alone branches of Barclays Bank, say, where natural associations may lead most of your targets to be white hot with indignation or black with despair. It is also not much use soliciting people who are in a tearing hurry.

Such results are exactly what the research excellence framework will admire. They have "impact". They could make a real difference to where and when people outside academe - redundant humanists, for example - put their begging bowls. In the bad old days, if someone such as myself had supposed these things to be true because we guessed that people behave better when they are in a good mood than when they are in a filthy mood, or because we had read it in Francis Bacon or David Hume, that would not have counted as research and couldn't have entered the REF. But the beauty of the new scientific synthesis is that if we test these insights and confirm them via careful experiments (p<0.05), they will.

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I enjoy new results. But I also venerate philosophical armchairs. They have, after all, sometimes been occupied by acute and rigorous thinkers, and for that matter imaginative and experienced observers of human life. I can't claim that for my own, but I can say that it is surrounded by a mountain of books, enabling me to enlarge what I observe myself of people and their doings.