After thirty-five years of correctional experience as warden of San Quentin prison during which Mr. Dully established himself as one of the most progressive rehabilitators, in the country, he can speak with authority On the causes of crime. Whe he says: ""Show me a prison and I will show you an inmate population that is at least 90 per cent sick. I believe in every single case, the sickness, directly or indirectly, has something to do with sex,"" you Can be sure that he speaks from a lifetime of intimate knowledge of the criminal mind. In this book, written with a Will Rogers informality, he proves his point. Causes, crimes, rehabilitation, adjustment- these are the major issues. The various types of Criminals are studied and particularly effective are his conversations with many of these men. Mr. Duffy calls for a major revision of attitude and penal policy...he is a strong advocate of Mexico's system of the conjugal visit- ""the most potent weapon for good behavior ever devised."" This is an eloquent appeal for an end to the ""Puritan"" avoidance of the sex issue on both sides of the wall.