the general principle that psychic forces and energies tend to remain in a steady or balanced state or tend to seek a return to a state of balance or of decreased energy. The idea is related to other general conceptions of constancy found in many scientific fields. In the psychology of Sigmund Freud, constancy refers specifically to the tendency of psychic energy, or libido, to seek a homeostatic or balanced state. The same principle lies behind Freud’s notion of catharsis.