The author of this little brochure believes that most psychiatric historians, even though recognizing St. Thomas's contributions to philosophy and normal psychology, have not appreciated his references to the psychiatric disorders. Nevertheless in the actual construction of his thesis the author finds that he must also present a summary of the psychological theories, and the result is that these fill thirty-three of the forty-five pages. St. Thomas, as is well known, advanced some concepts which fit in very well with certain modern theories, since he was much aware of the presence