Sigmund Freud (1856-1939): Topic PageSigmund Freud was the founder of psychoanalysis and proved to be the most influential writer about the unconscious mind in the twentieth century. In 1900, he published The Interpretation of Dreams, which became a seminal work in the history of psychoanalysis. Not only did it include his ideas about the unconscious and the conscious, it also revealed Freud’s tendency to view many psychological conflicts as rooted in sexuality.