Again it is a pleasure to me to acknowledge help and criticism of this book from a number of colleagues and friends who have read it in proof.

Professor Elliott Jaques, Miss Betty Joseph, Mr Money-Kyrle and Dr H. Segal have all helped with advice and criticism. I am also indebted to Dr J. O. Wisdom1 for many helpful criticisms of my previous work, and in particular of Learning from Experience, which have made me more aware of the pitfalls in this one. But whether I have avoided them is another matter. I would thank them all, but would not have them debited with my faults.

As always there remains my debt to my wife which I can acknowledge but cannot repay.

W. R. Bion