Freud begins by noting that although humanity has been fascinated by dreams for thousands of years, they have never been the subject of rigorous scientific investigation. The opening section attempts to throw off the skeptical scientific assumption that dreams are meaningless, and criticises simplistic explanations relying on the notion that 'somatic', physical stimuli felt during sleep produce mental pictures. Freud offers evidence that the sleeping mind can still function to a high level, albeit in a distorted fashion similar to that produced by some mental illness.
Next we have accounts of numerous dreams that have either been reported to Freud or which he has experienced for himself. These are used to make the argument that all dreams, regardless of their manifest content, function as the fulfilment of latent wishes. The ‘dream-distortion’ which disguises these fantasies with cryptic imagery results from the fact that they fulfil socially unacceptable desires, concealed from the conscious mind by a monitor which censors them even during sleep. Freud goes on to consider the role of memories from infancy in dream formation, speculating that the wishes fulfilled in dreams might be frequently, or even invariably, carried over from childhood. Roughly halfway through the book he drops his most potent theoretical bombshell, asserting that all children mimic the legend of Oedipus by directing their first feelings of sexual desire and jealous rage towards their own parents.
The next section focuses on the specific 'work' which dreams perform on the sleeper's unconscious material, condensing many varied thoughts into dense symbolic packages, while displacing uncomfortable fears or desires onto safer terrain. Freud also confronts some of the obvious objections to his theories, including the apparently meaningless absurdity of dreams, and the difficulty of distinguishing dream material that is truly ‘remembered’ from that which might be inadvertently ‘invented’ in the attempt. Freud goes on to outline a structure for his theory of the unconscious mind in technical terms, complete with scientific diagrams illustrating how its various components interact and conflict with one another. He concludes by reassuring the reader that, although the unconscious activity revealed by dreams says much about the origins of a person's character, it will only influence their actions in waking life if they remain unaware of it.