"Smart is the new sexy." It's a great notion. But this campaign slogan from the US newspaper industry, designed to arrest falling circulations, seems hopelessly optimistic in a society entranced by the comforting illusion that ignorance is bliss.

Wilful stupidity seems to have invaded some areas of public discourse, with climate-change denial and creationism emblematic of the malaise. Gerald Graff, professor of English and education at the University of Illinois at Chicago, warns in our cover story that society is being afflicted by "a kind of know-nothing anti-intellectualism that is shockingly pervasive, outrageous and dismissive of scientific opinion". Belief and prejudice, it is argued, are replacing knowledge as the foundations of public discourse. Why?

The academy has to accept some responsibility for this lamentable state of affairs. Scholars seem reluctant to try to shake students out of their utilitarian, employment-driven mentality, which makes them disinclined to question and argue. Academics are often unwilling to stand up and be counted in some of the most contentious - and vital - debates on and off campus.

No doubt there is the fear of student complaints, of being publicly shouted down and hounded by the cranks and shock-jocks whose ranks are reaching alarming proportions in the US. Then there's the risk of being outmanoeuvred and outgunned by well-funded lobby groups and partisan "thinktanks". There's also an element of snobbery at play: who wants to be accused of dumbing down for television?

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It is true that in pursuit of their journal-driven research careers, many campus intellectuals lack the space and incentives to become public intellectuals. But perhaps it should not surprise us that academics are shy of stepping on to public platforms when many who have done so have been ignored or slapped down by the politicians who asked them to come forward.

The UK's New Labour government championed "evidence-based policy", but there were many controversies about it censoring research on crime and education. In 2009, towards the end of Labour's era in power, David Nutt was sacked as chair of the Advisory Council on the Misuse of Drugs after he said one too many things that ministers disagreed with.

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And although the coalition pushes to ensure the "real-world" impact of research, the phenomenon described as "knowledge resistance" by Philip Schlesinger, chair in cultural policy at the University of Glasgow, seems alive and well. In the summer, the Home Office had to be reminded by a Commons select committee that it was ignoring evidence in tightening student-visa rules. Just last week, a report from the Campaign for Science and Engineering warned that Whitehall's scientific advice network was blighted by "wildly inconsistent support mechanisms" and that some chief scientific advisers were unable to fulfil their briefs.

In the UK, recent debates on the future of universities and the NHS, on abortion and welfare cuts, all seem to have suffered from the use of highly contestable, unsourced "facts" or the absence of a robust evidence base.

As long as our political classes are locked in a culture of policy-based evidence-making, we'll never have evidence-based policymaking. In this environment, the seekers of truth will keep their heads down, and public discourse and society will suffer.

phil.baty@tsleducation.com.