SCIENTISTS ARE, by and large, left-wing creatures. They opposed the Bomb. They generally oppose the destruction of habitats, which aligns them with the green movement. They have, broadly, chosen not to look at whether we are born geniuses or dunces, hippies or murderers; the spectre of genetic determinism conflicts with the cherished liberal notion that we, with the help of parents and society, shape our talents, opportunities and destinies.

They believe that scientific research should be conducted for the sake of truth and the benefit of society, rather than to line the pockets of shareholders; this makes them enemies of big business. They tend to believe in evolution, which puts them at odds with the pious. They aspire above all else to objectivity, impartiality and accuracy, and they respect the power of science to overturn old orthodoxies.

Now consider this: public policy on such topics as climate change and stem-cell research requires a scientific input. In America, public policy is moulded by a conservative, industry-friendly, Christian-sympathising Republican Government. The result, Chris Mooney documents in The Republican War on Science, has been an almighty intellectual clash between scientists and politicians.

This thick, detailed study is a controversial talking point in the US. Mooney takes several unrelated debates — on climate change, stem-cell research, whether sugary drinks are nourishing obesity, whether abortion harms women — and stitches them together to form the bigger picture. Despite the sometimes crudely partisan line, he weaves a pretty convincing tapestry.

Scientific advice, he writes, has been ignored, undermined, distorted or spun, and uncertainties magnified or even manufactured. “Science politicisation,” he declares grandiloquently, “threatens not just our public health and environment, but the very integrity of American democracy, which relies heavily on scientific and technical expertise to function.”

Climate change is a notorious example — James Inhofe, one of President Bush’s leading environmental spokesmen, has consistently disputed the clear consensus that human activity is causing a build-up of greenhouse gases.

And when scientists complain of interference, they are beaten with their own liberal stick. Robert Walker, Bush’s science adviser during the 2000 presidential campaign, said that “a lot of the scientists come out of large universities where there is a basically left-wing political bias on the campus . . . (they have) bought into a political agenda inside the atmosphere in which they operate.”

Walker’s subtext, it appears, is that scientists need taking down a peg or two; the American Government has obliged.

There are cases of researchers who apply for appointments on influential committees being asked how they voted and for their views on abortion. The federal agency regulating the impartiality of scientific advice to Government has been scrapped. Government scientists must now ask permission to attend international conferences, and they are instructed to act as advocates of government policy.

Fringe scientists — the “contrarians” who disagree with the scientific consensus — can be used to sow convenient doubts. They are pressed into media service to offer a dissenting view, conveying the spurious impression that the scales on, say, climate change, are stacked evenly either way. Mooney describes this diversion tactic as a “breeding ground for disingenuousness . . . as fringe and pseudo-scientific arguments make their way into the public sphere . . .”

However — and Mooney doesn’t fully explore this, although he refers to it — those on the Left can be just as guilty of disingenuousness. In particular, environmental pressure groups still claim, without credible scientific evidence, that genetically modified foods are harmful to health and that organic produce is healthier than non-organic produce (the real scientific debate is over whether GM crops harm the environment; there is evidence that organic farming is more environmentally friendly).

While the trend of questioning scientists more robustly is a welcome one, the lack of deference is fast degenerating into a lack of respect for how science works. Because of this, the public is slowly, and rather dangerously, coming to believe that science is an opinion-based activity rather than an evidence-based one.

Usually, a scientific consensus is a consensus because it really is the best explanation of what’s going on. Experiments are conducted and theories are developed that fit with observations; the theory makes predictions that are later fulfilled. Other scientists versed in the field provide a critique of this work, mostly anonymously, so that it meets a minimum standard of competence.

Now consider intelligent design, which contends that evolution could not have produced the biological complexity we see today. It has absolutely no peer-reviewed scientific evidence or theory behind it (other than, basically, “God did it”) and is untestable. Its advocates, rather shrewdly, provoked outrage from biologists, and then announced that there was a “controversy” to teach. Bush fell for it. He would like schoolchildren to learn about intelligent design alongside evolution.

Believe the contrarian if you wish, but remember that for every Galileo, the pin-up of the scientific heretics’ movement, there are a thousand cranks.

Anjana Ahuja writes Science Notebook in The Times

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