Steven Rose offers a piece of moral advice in his Commentary 'Should scientists study race and IQ?' (Nature 457, 786–788; 2009). To instruct humankind that they should not do something is a serious undertaking: it should be clear what is enjoined and the consequences acknowledged.

Rose seems to argue that, by about 1975, it should have been clear to everyone that the question of genetic causes behind the black/white IQ gap was unanswerable. From that date, there was no excuse for Arthur Jensen or anybody else to persist.

I invite everyone to search the social-science literature of the past 34 years and ask whether or not they really wish that everything on the subject, pro or con, was missing. I thought that the first replies published to rebut Jensen were pathetic, and still do. Others must judge the value of my subsequent book Race, IQ and Jensen (Routledge & Kegan Paul; 1980); the theory of intelligence that limits g — the 'general intelligence factor' — to explaining individual differences; the Dickens–Flynn model of the interaction of genes and environment; the analysis of the achievements of Chinese–Americans, and so forth. More distinguished contributions have been made than those that I have offered.

Imagine that IQ tests showed black American children having, on average, a 15-point IQ advantage over white children. How many of us would denounce that finding as meaningless? Or would we be waving it like a banner, as evidence that only racists would attempt to dismiss? The scientifically respectable has a way of shifting, depending on how one thinks the debate is going.

As the philosopher John Stuart Mill points out, when you assert that a topic is not to be debated, you are foreclosing not some narrow statement of opinion on that topic, but the whole spiralling universe of discourse that it may inspire. Mill thought that only someone so self-deluded as to think his own judgement was infallible could wish to circumscribe an unpredictable future in this way.

Rose should be very certain he is correct. If not, and if he converts the rest of us, only Jensen and those of his persuasion will publish; and they will win the minds of students because the rest of us have all adopted a policy of unilateral disarmament.

See also: The belief that genes cannot be changed is now outdated Identifying adaptive differences could provide insight The arrogance of trying to sum up abilities in a number Is poverty better explained by history of colonialism? Measured intelligence is a product of social processes Don't fan the flames of a dead debate A useful way to glean social information