A work of genius is a complex object and there is light to be shed about what went into the making of it. Even in the case of scientific and mathematical achievement we can say a great deal about the existing state of knowledge, the problems it failed to address, why those problems were or had become interesting, the particular capacities which the solver brought to their solution. At the other extreme is a work of art which seems to have much more immediate roots in the personal life of the artist or writer. In between is the area in which Keynes worked, which was partly scientific, partly artistic. This gives a wide justification for a biographical approach. As I put it in the introduction to my first volume: 'If underlying Keynesian theory was Keynes's vision of his age, knowledge of his state of mind and the circumstances which formed it is essential, not only in order to understand how he came to see the world as he did, but also in order to pass judgement on the theory itself.