The Unconscious
From Freud, Sigmund. A Note on the Unconscious in Psychoanalysis. As reproduced in Sources of the Western Tradition, trans. Joan Riviere, ed. Marvin Perry, Joseph R. Peden, and Theodore H. Von Laue, vol. 2 (Boston: Houghton Mifflin Company, 1999), 276.
Sigmund Freud delivered the following lecture in 1909, which was published in 1912. Freud (1865-1939) defined the term "the unconscious" and its application in psychoanalytic theory and practice. The idea of the unconscious, however, would grow to have implications beyond the psychoanalytic treatment of mentally diseased individuals; for Freud and others, it came ultimately to denote a fundamental, and fundamentally well-hidden, part of human nature--perhaps even its core. In later works, such as Civilization and Its Discontents, Freud would go on to apply his psychoanalytic techniques to the study of human society in general and western civilization in particular.
 
I wish to expound in a few words and as plainly as possible what the term 'unconscious' has come to mean in psychoanalysis and in psychoanalysis alone. . . .

The well-known experiment, . . . of the 'post-hypnotic suggestion' teaches us to insist upon the importance of the distinction between conscious and unconscious and seems to increase its value.

In this experiment . . . a person is put into a hypnotic state and is subsequently aroused. While he was in the hypnotic state, under the influence of the physician, he was ordered to execute a certain action at a fixed moment after his awakening, say a half an hour later. He awakes, and seems fully conscious and in his ordinary condition; he has no recollection of his hypnotic state, and yet at the prearranged moment there rushes into his mind the impulse to do such and such a thing, and he does it consciously, though not knowing why. It seems impossible to give any other description of the phenomenon than to say that the order has been present in the mind of the person in a condition of latency, or had been present unconsciously, until the given moment came, and then had become conscious. But not the whole of it emerged into consciousness: only the conception of the act to be executed. All the other ideas associated with this conception--the order, the influence of the physician, the recollection of the hypnotic state, remained unconscious even then. . . .

The mind of the hysterical patient is full of active yet unconscious ideas; all her symptoms proceed from such ideas. It is in fact the most striking character of the hysterical mind to be ruled by them. If the hysterical woman vomits, she may do so from the idea of being pregnant. She has, however, no knowledge of this idea, although it can easily be detected in her mind, and made conscious to her, by one of the technical procedures of psychoanalysis. If she is executing the jerks and movements constituting her 'fit,' she does not even consciously represent to herself the intended actions, and she may perceive those actions with the detached feelings of an onlooker. Nevertheless analysis will show that she was acting her part in the dramatic reproduction of some incident in her life, the memory of which was unconsciously active during the attack. The same preponderance of active unconscious ideas is revealed by analysis as the essential fact in the psychology of all other forms of neurosis. . . .

The term unconscious . . . [thus] designates . . . ideas with a certain dynamic character, ideas . . . [divorced] from consciousness in spite of their intensity and activity.