A term loosely applied to all forms of psychoanalysis, alluding to the dynamic interplay of psychological process and phenomena arising from instincts (3) that facilitate, inhibit, and combine with one another, or produce compromise formations. In 1909/10, Sigmund Freud (1856–1939) distinguished his theory of the split between consciousness and the unconscious (2) from static theories that had gone before: ‘We explain it dynamically, from the conflict of opposing mental forces, and recognize it as the outcome of an active struggling on the part of the two psychical groupings against each other’ (‘Five Lectures on Psycho-Analysis’, Standard Edition, XI, pp. 9–55, at pp. 25–6). See also depth interview, depth psychology, metapsychology, motivational research.