It's becoming something of a New Year ritual. For almost a decade, the website www.edge.org [5] has been asking a selection of eminent thinkers and scholars to answer a single question and publishing the results on 1 January.

In the past it has presented such posers as "What do you believe is true, even though you cannot prove it?" and "What is the most important invention of the past 2,000 years?"

This year Edge wanted to know: "What have you changed your mind about and why?" As usual, it's a good question. And the responses of the likes of Steven Pinker and Helena Cronin are as fascinating and weighty as one would imagine.