Definitions for "existentialism"
a philosophical theory or attitude having various interpretations, generally emphasising the existence of the individual as a unique agent with free will and responsibility for his or her own acts, though living in a universe devoid of any certain knowledge of right and wrong; from one's plight as a free agent with uncertain guidelines may arise feelings of anguish. Existentialism is concerned more with concrete existence rather than abstract theories of essences; is contrasted with rationalism and empiricism; and is associated with Kierkegaard, Heidegger and Sartre, as well as others.
This is both a philosophical and literary movement which teaches that: Individual existence takes precedence over abstract concepts; humans are totally free and responsible for their own actions; no absolute values exist that are not grounded in human experience.
A philosophy whose central concern is the human subject’s ‘being’ in the world. Existentialism gives primacy to existence and then to essence. Among its main position is that all persons are estranged from their creativity and live in a world of objects; any attempt to realize a true human condition is to enter a struggle against estrangement.
a highly diverse and even contradictory system of thought that was loosely united in a courageous search for moral values in a world of terror and uncertainty. (p. 925)
Keywords:  belief, chooses, basic, live, shapes
the belief that one shapes one's basic nature through the direction of life one chooses to live.