Pessimism is the only effective indemnity against disappointment. Optimists are doomed by complacency. Pessimists are forearmed against peril. Optimists are gamblers who sometimes get lucky breaks but usually overplay their hands. In the long run pessimists outdo them with the unspectacular gains of caution, and outlive them by preparing for the worst. In the race of life, optimists are hares – bounding and reckless – while pessimists are tortoises, inching and defensive. Optimism has the advantages of elegance and flair. Pessimism is the more informed, more modest, and more reasonable option. Yet Matt Ridley, who is an excellent biologist and ought to know something about how to adapt for survival, proclaims himself a ‘rational optimist’. He used to be chairman of Northern Rock, but still navigates with the sirens. He should see where optimism leads, but seems irresistibly drawn towards risky speculations.

His new book exhibits his characteristic virtues: trenchancy, fluency, wit and dazzling command of diverse material. In one respect, however, it is a curious departure from his previous work. Formerly, as he admits,