With a book already so well-known little seems needed by way of Preface. Itis a brilliant example of the way in which knowledge based on the detailed psycho-analysis of living persons can be made use of to throw light on the deeper springs of character in those whose mind is not accessible to direct investigation. Tl£process is, therefore, akin to a piece of archaeological reconstrnction. The study is based on the solitary mention Leonardo makes of his childhood, evidence which most psychologists would have passed by as being ?imsy and meaningless but its unique occurrence and extraordinary nature both call for explanation, if we are not to dismiss such happenings as being causeless. Professor Freud has dealt with it by comparing it with similar phan tasies analysed by him and with other known facts of Leonardo's life. In the fascinating study resulting from this procedure he has thrown a flood of light on one of the most remarkable and interesting personalities of history.