Sigmund Freud is the most famous psychologist who ever lived, and possibly the most influential thinker of the 20th century. His ideas, the unconscious, repression, the Oedipus complex, defense mechanisms, the talking cure, have permeated Western culture so thoroughly that people use Freudian concepts without knowing they are Freudian. When you talk about Freudian slips, unconscious desires, or being in denial, you are speaking Freud’s language. When you assume that childhood experiences shape adult personality, that dreams have hidden meanings, or that people are motivated by forces they do not understand, you are thinking Freudian thoughts. He did not just...