The editor and literary agent John Brockman recently challenged the salon of scientists that he hosts on his website by asking: 'What is the most important invention of the past two thousand years?' Not content to be merely right, his contributors vied for originality, provocativeness and intellectual panache. This book provides a showcase for more than a hundred of their responses, which are as varied, and in some cases strange, as the participants themselves. Gutenberg's printing press wins the most endorsements and passing nods. But the neuroscientist Colin Blakemore and others argue for the birth-control pill. The biologist Richard Dawkins nominates the spectroscope. The physicist Freeman Dyson makes a case for hay. John Maddox, the former editor of Nature, favours the calculus.