It was used in older psychology and philosophy as meaning the source or cause of human nature. It is not a scientific term, but the word "psychology" is derived from it. The English word soul was sometimes used synonymously in older texts.
- Hillman J (1989). A blue fire: Selected writings by James Hillman. New York, NY, USA: HarperPerennial. p. 20.
- Reber A.S. & E.S. 2001. Dictionary of psychology, p577. 3rd ed, Penguin Reference.