"One of the oddities of Hayek’s career is that while his professional standing was secured through his work as an economist, he had by the mid-1940s given up economics as his central intellectual activity. A major reason for Hayek’s shift into social philosophy was that he believed – correctly – that he had lost the debate with John Maynard Keynes about the causes of the Great Depression. There can be no doubt that his encounter with Keynes was the most important event in his intellectual life. Yet he had little insight into Keynes either as a thinker or a human being. He told me that during their acquaintance he never realised that Keynes had been homosexual – a surprising admission, as it was hardly something Keynes concealed within his circle of friends. The two men had quite different kinds of minds – Keynes’s swift and mobile, with an almost clairvoyant power of entering into the thinking of others; Hayek’s slowly probing, inwardly turned and self-enclosed. They were nonetheless on cordial terms. Keynes found Hayek rooms in King’s College when the London School of Economics (where Hayek became a professor of economics in 1931) moved to Cambridge for the duration of the Second World War, and for a time the pair shared fire-watching duties on the roof of the college when it was feared that Cambridge might be bombed. With characteristic generosity, Keynes – while firmly rejecting its claim that government management of the economy is bound to lead to totalitarianism – heaped praise on Hayek’s anti-socialist tract The Road to Serfdom when it appeared in 1944. The differences between the two thinkers were as much in their underlying philosophies as in their economic theories. Both were sharply aware of the limits of human knowledge. But whereas Hayek invoked these limits to argue for non-intervention in the economy, Keynes recognised that bold action by governments is sometimes the only way in which the economy can be lifted out of depression – as when Roosevelt (to whom Keynes had written an open letter in 1933) successfully adopted some aspects of Keynesian thinking in the New Deal."