In psychoanalytic theory, the three levels of consciousness as outlined by Sigmund Freud are the conscious, preconscious and unconscious minds. Freud likened this theory to an iceberg with a visible tip, the conscious mind; an obscured but visible middle, the preconscious; and a bulk hidden beneath the water, the unconscious.
In Freud's model of the mind, the conscious mind is formed by the thoughts and feelings that a person is actively aware of and able to reason about. The preconscious is made up of all available memory that has not been accessed by the conscious mind. The unconscious mind consists of repressed instincts, feelings and urges that are negative or shameful. Freud theorized that the preconscious and unconscious exert a powerful influence over the conscious mind without a person's awareness.