Paul Nurse, president of Britain's Royal Society, does not think he is sitting in an ivory tower, and he has made it clear that he considers that scientists have duties to fulfil and battles to fight beyond the strictly scientific — for example to “expose the bunkum” of politicians who abuse and distort science. This was evident again last week, when Nurse delivered the prestigious Dimbleby Lecture in London, instituted in memory of the British broadcaster Richard Dimbleby.

Nurse identified support for the National Health Service, the need for an immigration policy that attracts foreign scientists, and inspirational science teaching in primary education as some of the priorities for British scientists. These, and many other issues he raised, such as increasing scientists' interactions with industry, commerce and the media, and resisting the politicization of climate-change research, are relevant throughout the world and not just in Britain.

All the more reason not to misinterpret Nurse's insistence on a separation of science and politics: as he put it, first we need the science, then the politics. What Nurse rightly warned against is the intrusion of ideology into the interpretation and acceptance of scientific knowledge as, for example, in the Soviet Union's support of the anti-Mendelian biology of Trofim Lysenko. Given recent accounts of political interference in climate research in the United States (N. Oreskes and E. M. Conway Nature 465, 686; 2010), this is a timely reminder.

The practice of science is inherently political.

But it is easy to render this equation too simplistically. For example, Nurse also cited the rejection by Adolf Hitler of Albert Einstein's relativistic physics as 'Jewish physics'. But that is not quite how it was. 'Jewish physics' was a straw man invented by the anti-Semitic and pro-Nazi physicists Johannes Stark and Philipp Lenard, partly because of professional jealousies and grudges. The Nazi leaders were, however, largely indifferent to what looked like an academic squabble, and in the end lost interest in Stark and Lenard's risible 'Aryan physics' because they needed a physics that actually worked.

That is one reason to be sceptical of the common claim, repeated by Nurse, that science can flourish only in a free society. Historians of science in Nazi Germany such as Kristie Macrakis (in her book Surviving the Swastika) have challenged this assertion, which is not made true simply because we would like it to be so. Authoritarian regimes are perfectly capable of putting pragmatism before ideology. The scientific process itself is not impeded by state control in China — quite the contrary — and the old canard that Chinese science lacks innovation and daring is now transparently nonsense. During the cold war, some Soviet science was vibrant and bold. Even the most notorious example of state repression of science — the trial of Galileo — is apt to be portrayed too simplistically as a conflict of faith and reason rather than a collision of personalities and circumstances (none of which exonerates Galileo's scandalous persecution).

There is a more compelling lesson to be drawn from Nazi Germany that bears on Nurse's themes: although political (and religious) ideology has no place in deciding scientific questions, the practice of science is inherently political. In that sense, science can never come before politics. Scientists everywhere enter into a social contract, not least because they are not their own paymasters. Much, if not most, scientific research has social and political implications, often broadly visible from the outset. In times of crisis (like the present), scientists must respond intellectually and professionally to the challenges facing society, and not think that safeguarding their funding is enough.

The consequences of imagining that science can remain aloof from politics became acutely apparent in Germany in 1933, when the consensus view that politics was, as Heisenberg put it, an unseemly “money business” meant that most scientists saw no reason to mount concerted resistance to the expulsion of Jewish colleagues — regarded as a political rather than a moral matter. This 'apolitical' attitude can now be seen as a convenient myth that led to acquiescence in the Nazi regime and made it easy for German scientists to be manipulated. It would be naive to imagine that only totalitarianism could create such a situation.

The rare and most prominent exception to apolitical behaviour was Einstein, whose outspokenness dismayed even his principled friends the German physicists Max Planck and Max von Laue. “I do not share your view that the scientist should observe silence in political matters,” he told them. “Does not such restraint signify a lack of responsibility?” There was no hint of such a lack in Nurse's talk. But we must take care to distinguish the political immunity of scientific reasoning from the political dimensions and obligations of doing science.