The Beautiful / An Introduction to Psychological Aesthetics

Taboo and Genetics / A Study of the Biological, Sociological and Psychological Foundation of the Family

A Text-Book of Astronomy

The Biology, Physiology and Sociology of Reproduction / Also Sexual Hygiene with Special Reference to the Male

The Mystic Will. A Method of Developing and Strengthening the Faculties of the Mind, through the Awakened Will, by a Simple, Scientific Process Possible to Any Person of Ordinary Intelligence

The Psychology of Nations / A Contribution to the Philosophy of History