Claims 2 innate drivers (both in the unconscious): Eros (Libido) + Thanatos (death wish)
Regard human behaviour as interaction between opposing forces
Libido:
Life instinct
Manifests as sexual motives
Focus on preservation + life enjoyment
Thanatos:
Death instinct/wish
Manifests in aggression + destructiveness
To prevent self-harm, Thanatos is projected or displaced
Catharsis control by defence mechanisms
Catharsis:
Safe mental energy release
Vent mental pressure; psychoanalysis
Failure to release causes mental health issues + aggression (hydraulic model)