'Inevitably, it raises a question about the purpose of biography. In reviewing the first volume of my own life of Keynes, the economist Maurice Peston wrote: ‘What help is knowledge of the lives of Newton and Einstein in predicting the movement of the planets?’ To which the answer is that economics is not a natural science like physics. One needs to know the economist, and his location in the flow of events, not to test his theories but to judge their value for our own time.'