Freud believes that by examining how the mind responds to the trauma of external danger, psychoanalysts can gain insight into how the mind processes and internalizes other types of traumas. World War I helped to shape an understanding of the impact of traumatic events, removing the former clinical assumption that symptoms were related to nervous disorders. Freud suggests that when humans experience traumatic events, they first react in one of three ways: fright, fear, or anxiety. Each has its own definition and relation to danger. Freud proposes that when humans do not experience a wound during the event, they are more likely to develop psychological effects.

Dreams play a key role in uncovering the working of the unconscious mind and the impact of trauma. Freud suggests that when humans are in states of neuroses, they repetitively engage in their traumatic experiences in their dreams. Although their nights are filled with the repetitive images of their trauma, their days are filled with avoidance.

Freud relates the repetitive engagement with trauma to the repetitive nature of children’s play. He critiques theories about children’s play that ignore the role of the pleasure principle. Play has an economic advantage; children select play based on the amount of pleasure they will receive from it.