It was my friend Bill that started it. 'Come to the Science Cafe', he said. That was ages ago, and I've been to every one since (apart from the one on football). Monday saw Dick Taverne talking on the theme of his book, The March of Unreason. He delivered a polemic against the Precautionary Principle.
The format of the Science Cafe is a half-hour talk, followed by questions. All of the questions were sympathetic to the Baron. He is an accomplished speaker, and his arguments so compelling that nobody was willing to risk ridicule by challenging him. Then an earnest red haired student asked, 'if not the Precautionary Principle, then what should guide policy?'. The Baron answered, 'scientific evidence should guide such decisions'. I asked, 'What do you do in the absence of scientific evidence?', he paused on the horns of a dilemma. If he said, 'you go ahead anyway', then that's obviously reckless, but if he said, 'you don't do anything until the evidence comes in', then that's the Precautionary Principle. In the end he gave a non-answer, waffling.
Having said that, I agreed with much of what Dick Taverne had to say. He argued that we should take science seriously, and I totally agree with that. Where he veered off course was when he conflated science and morality.
Warning: Threat to belief system. In thinking of the challenges it was possible to make to Taverne, I saw the openings of problems with David Deutsch's ideas in 'The Fabric of Reality', on which I have based my entire world view.