In his final chapter, Freud tries to show that his dreams theory follows from larger principles about the way our minds work.

Wish-fulfillment, he argues, is a very old function, embodied, even, by the nervous system, which operates to discharge excitation. Dreaming, as psychically primitive, realizes that function, and only that function. It is set in motion by a wish that, if unattended, would wake us. A dream, fulfilling such a wish, allows us to sleep on. It hallucinates the fulfillment, hallucination of the mental equivalent of a reflex, serving the purpose of discharging an irritant.