Freud is best known for his theories of the unconscious mind and the defense mechanism of repression, and for creating the clinical practice of psychoanalysis for treating psychopathology through dialogue between a patient and a psychoanalyst. The 6 Tenets of Freud's Psychoanalytic Theory Although most of his theories have been modified or disproved, Sigmund Freud was essential in bringing the world of clinical psychology to the masses.