Existential psychology is based--reasonably enough- -on existential philosophy. Existential philosophy grew out of the nineteenth century writings of Soren Kierkegaard and Frederick Nietzsche, and was later elaborated in the "phenomenological" philosophies of Husserl and Heidegger. In the 1940's, the theories of existentialism were given a name, and an enormous boost in popularity, by Jean- Paul Sartre, Albert Camus, and other European intellectuals who had suffered through World War II and come out on the other side with a philosophy that focused on self-reliance, authenticity, responsibility, and mortality. How did this philosophy get translated into psychology?

One way was through the philosophers: Sartre himself wrote extensively on the "psychology" of everyday behavior, imagination, and other topics. Another way was through psychologists who were intrigued by the philosophical claims of existentialism and the opportunities it offered to escape the dominating theories of psychoanalysis.

The following description of existential psychology is founded mostly from the writings of Rollo May, one of the more philosophically-minded of the humanistic psychologists.

Why are existential psychology and philosophy called "existential"? The reason is that they focus on existence in the here and now. At each moment, a person is free to choose what he or she will do and be. The most important aspect of a person is not what she has genetically inherited, or how her parents treated her when she was an infant, but how she interprets and responds to the world around her at each given instant, and the kinds of choices she makes about what to do next. Thus, existential and humanistic psychologies reject Freud's claim that the most important factor in understanding a person is early life experience. It also rejects the idea that biological or inherited factors are the most important aspect of a person (though only the most radical and misguided existentialist would claim that such factors have no influence on behavior). Furthermore, conscious choice and responsibility are central to existential psychology, and the unconscious is given little or no role to play.

If existential psychology rejects sex and death as the fundamental motive forces behind behavior, then why do people act at all? Existential psychology has two answers, one negative, called existential Anxiety, and one positive, called existential freedom.