It's pleasing to see, in the storm of commentary over Professor David Nutt's sacking as the government's chief drugs adviser, that everyone outside politics now recognises the importance of scientific evidence in devising laws. But a strange reasoning twitch has appeared, in the arguments of politicians and rightwing commentators. Science can tell us about the molecules, they say, about their effect on the body and the risks. But policy is separate: a matter for judgment calls on social and ethical issues. Only politicians, they say, can determine the correct way to send out a clear message to the public. It is not a matter for science.This is wrong. Alongside research into the risks of drugs, lots of work has also ...