Beyond the Pleasure Principle opens with a puzzle. Psychoanalysis had built its picture of mental life around the pleasure-principle: the psyche seeks to discharge tension and attain pleasure, and where it fails, it does so because the reality-principle imposes delay. But Freud is troubled by cases that this framework cannot explain: patients who dream, night after night, of the trauma that shattered them, and who seem compelled to repeat, rather than remember, their worst experiences.
To explain this, Freud observes a child's play. His grandson repeatedly throws a reel over the edge of his cot with a sound meaning 'gone,' then draws it back with a joyful 'there.' The departure of the mother, a painful event, is being staged over and over. The child takes an active part in what he passively suffered. Freud names this the repetition-compulsion: a force in the unconscious that drives the re-enactment of painful experience independently of any pleasure-gain, and which seems more primitive than the pleasure-principle itself.
In the speculative middle sections, Freud offers a biological account. He models the psyche as a living vesicle protected by a barrier against stimuli. Trauma is what breaches this barrier; traumatic dreams are the mind's attempts to master the flood of excitation after the fact by repeatedly returning to the scene. But the repetition-compulsion runs deeper than trauma alone. It appears throughout neurotic life and even in the destinies of normal people who seem condemned to the same patterns of failure and loss.
Freud then advances his most radical hypothesis: that instincts are essentially conservative, aiming to restore an earlier state. If this is so, the deepest drive in living matter is to return to the inorganic condition from which it arose. Life is a long, circuitous detour toward death, and the death drive, the pressure toward quiescence, toward the Nirvana-principle, underlies all organic existence. Freud acknowledges frankly that this is speculation, not established theory.
The life instincts, Eros, stand in opposition. Sexual reproduction, the binding together of cells, the formation of more complex organisms: all represent Eros working against dissolution. In drawing this contrast Freud arrives at a dualistic picture of all mental and biological life: the striving of Eros to hold things together against the pull of the death drive toward the peace of the inorganic. He closes not with certainty but with an honest assessment of his own speculative method, comparing scientific progress to limping rather than flying.