Sigmund Freud (1856-1939) is known as the "father of psychoanalysis" and his ideas, however controversial, were fundamental in shaping how the human mind has been studied. The Interpretation of Dreams (1900) is a seminal work; in it, Freud seeks to show how analysis of dreams reveals symbols-keys to the workings of the unconscious mind. Beyond the Pleasure Principle (1920) is an important turning point in Freud's thought, as he argues that human life is not only ruled by the creative drive for pleasure, but also by the struggle against destruction and death.