The question of whether biotechnology should be deployed to improve human beings morally is starting to climb out of the pages of recondite publications and dip a quizzical toe in mainstream media. A recent article in the Telegraph quotes Professor Julian Savulescu from the Oxford Uehiro Centre for Practical Ethics saying that, should it ever become possible, the use of genetic technology to screen out morally unworthy characteristics should be morally obligatory. “When it comes to screening out personality flaws, such as potential alcoholism, psychopathy, and a disposition to violence, you could argue that people have a moral obligation to select ethically better children.” “We’re routinely screening embryos and foetuses for conditions such as cystic fibrosis and Down’s syndrome,” he continues, “and there’s little public outcry.”

It would of course be difficult to overstate the scale of man-induced misery in the world or the desirability of reducing it. Given that, on the face of it at least, a great deal of this seems to come down just to the kinds of things we human beings are, the possibility of using all available means to improve us seems attractive. But a swarm of problems immediately takes wing. Setting aside real doubts about the science here—are personality traits, if that is what we are talking about, really sufficiently encoded in single genes to leave them liable to biochemical tweaking?—one fairly obvious problem is what actually constitutes a morally desirable characteristic. In Croatia this summer I read Post War, Tony Judt’s densely woven history of Europe since the Second World War—the Balkans seemed like a good place to reprise that long half-century. Among the deadliest human passions that flared in those years was xenophobia, the fear and hatred of strangers or foreigners and their habits of life, a passion easily provoked to murderous extremes by fascist and nationalist demagogues. A good candidate then for biochemical Tippexing?

One of the difficulties here is paradox: the quite straightforward way in which human traits can simultaneously present opposing faces. A love of country and a passionate identification with fellow citizens have driven people to extremes of self-sacrifice. They have also given rise to murderous passions. If we act to eradicate the wellsprings of xenophobia, might we not also eradicate something desirable, the possibility of group-bonding itself perhaps? As Freud put it, “it is always possible to bind together a considerable number of people in love, so long as there are other people left over to receive the manifestations of their aggressiveness.” Freud, like many modernists was partial to a paradox and there are certainly sunnier takes on nationalism—a love of fellow citizens being a necessary first step to love of all the world’s citizens perhaps—but the complexity of what we are dealing with is clear. Given that emotions may have some cognitive content, conscious or not—emotions that is, frequently involve judgments—perhaps the better way forward would be to bring the judgments to light and criticise them rather than eradicate the passions that underlie them. After all, what is strange can easily become familiar.

If xenophobia looks like an unreliable target, what about the aggression that underlies it? Once necessary for survival, perhaps aggression is now a useless evolutionary hangover, a kind of emotional appendix. Perhaps we should bioengineer ourselves into a race of quiescent pacifists quietly cultivating our gardens? But is aggression always morally blameworthy? As Kenan Malik argues here in relation to the Arab Spring, the aggression deployed in resisting tyranny is hardly morally equivalent to the aggression of those who are doing the tyrannising. On a slightly different tack, would Andy Murray have won the US Open without focussed and disciplined aggression? Our moral lives cannot be reduced to a binary judgment of our passions, good or ill. Reality is more complex, more nuanced. It is linked to judgment, responsive to circumstance and always and necessarily amenable to trade-offs and compromise.

The proper work of moral philosophers is to philosophise and a lot of this has to do with interrogating the integrity of arguments. When it comes to their practical application, philosophers have been known loftily to wave them away with a dismissive—well that’s just policy. Perhaps it was the Judt, I don’t know, but what chills me most about moral enhancement is its potential impact on liberty. (For a strong liberty-based critique of moral enhancement to which I am indebted, see John Harris here.)  The dead decades of Soviet Eastern Europe glowering in my mind, just thinking about how it might work in practice brought me out in hives. A government-sponsored Committee presumably, populated by the wisest minds—so no possibility of error there then; a list of socially undesirable characteristics; the compulsory scanning of embryos; the whole-scale eradication of disruptive or anti-social “types?” Set aside the questionable science, the over-simplification of moral experience, the apparent equivalence between undesirable physical conditions—cystic fibrosis—and moral traits, surely you need a tin ear for recent history not to wonder just how this might pan out in practice.

As Harris makes clear though, what lies at the back of these arguments is a dispute about what constitutes a human being and what makes human life morally valuable. Those who favour moral enhancement seek to engineer us so that we simply have no choice but to act well. In one sense of course this would be quite straightforwardly a good thing. But in doing so we have to sacrifice our freedom to do otherwise. And in doing that we surely risk eradicating the most valuable part of what it is to be human.

Julian Sheather is ethics manager, BMA. The views he expresses in his blog posts are entirely his own.