The Fliess letters show how Freud used myths, religion, and literature in his self-analysis to discover and uncover the 'demons' of the unconscious. Freud defined the demon as the death instinct itself, which takes precedence over the pleasure principle as the regulator of man's destiny. In therapy, limitations in establishing control over the realm of the demons (instincts) is respected, but Freud warned against a number of temptations that lie in the pathway of the would-be analyst. Psychoanalysis is founded on truthfulness, and self-scrutiny of its techniques provides the best safeguard against the persistence of demons of the irrational in any form other than as instincts in the service of the ego.