Who is Sigmund Freud from Literary Theory: An Introduction and what is their importance?

Austrian, Sigmund Freud, formed the basis for the scientific study of psychology. He believed that all of humanity was psychologically split between what he called the pleasure principle and the reality principle. The pleasure principle causes a person to want to do what he finds pleasurable and satisfying. The reality principle is the realization that work must be done in order to survive. The reality principle thus must repress the pleasure principle, otherwise it would be impossible to do unpleasant but necessary work. Neurosis—or mental illness—arises when the repression of the pleasure principle becomes too extreme and the person literally can no longer tolerate it.