The pleasure principle governs the mental apparatus from the beginning. It aims at the avoidance of unpleasure and the attainment of pleasure — at the reduction of tension, the satisfaction of need. But this programme, Freud argues with characteristic pessimism, is structurally impossible to fully realize. Happiness, in the intense positive sense of the word, is episodic and transient; suffering is persistent and comes from three directions simultaneously: our own bodies (which decay), the external world (which is indifferent), and our relations with other people (which are the most painful of all).
Unable to achieve full happiness, humans adopt strategies for reducing unhappiness instead. Freud catalogues them with sympathetic irony: intoxication (the crudest but most effective chemical method), withdrawal from the world (the hermit's path), sublimation (redirecting instinctual energy into higher activity), love (the most risky, since it makes one utterly dependent on the beloved), and the enjoyment of beauty — which offers "mild narcotic" effects without the morning-after of intoxication.
Religion, in Freud's analysis, is the most totalizing of these strategies: it enforces a single method on everyone, guarantees happiness in exchange for submission, and achieves this by "a forcible fixation on an infantile state" — the acceptance of a cosmic father's care. What religion gains in security it sacrifices in reality-testing. The less consoling but more honest strategies admit the impossibility of full happiness and work within that constraint.
The analysis of the pleasure principle in the context of civilization extends Freud's earlier work in Beyond the Pleasure Principle (1920), which introduced the death drive as the pleasure principle's adversary.