Dr. Sheldon wrote The Varieties of Human Physique in which he made a systematic study of human morphological differences. In The Varieties of Temperament he presents a 'constitutional psychology' and proposes that it supplement general psychology.

Some Theoretical Considerations (Chapter VIII) should be read by all practicing psychoanalysts because the qualifications of a constitutional psychologist are so well discussed and the juxtaposition of psychology, psychiatry, and psychoanalysis so well stated.

Although constitutional analysis and freudian analysis are not totally unrelated procedures, Sheldon, with respect for their different methods and terminologies, sees the two approaches as upward and downward extensions, respectively, of a continuum. He says that freudians start with consciousness and go as far (down) as they can, whereas constitutional psychologists start with the solid