Self-actualization is a term that has been used in various psychology theories, often in slightly different ways. The term was originally introduced by the organismic theorist Kurt Goldstein for the motive to realize one's full potential. Expressing one's creativity, quest for spiritual enlightenment, pursuit of knowledge, and the desire to give to society are examples of self-actualization. In Goldstein's view, it is the organism's master motive, the only real motive: "the tendency to actualize itself as fully as possible is the basic drive... the drive of self-actualization." Carl Rogers similarly wrote of "the curative force in psychotherapy - man's tendency to actualize himself, to become his potentialities... to express and activate all the capacities of the organism." The concept was brought most fully to prominence in Abraham Maslow's hierarchy of needs theory as the final level of psychological development that can be achieved when all basic and mental needs are essentially fulfilled and the "actualization" of the full personal potential takes place, although he adapted this viewpoint later on in life, and saw it more flexibly. Self-actualization can be seen as similar to words and concepts such as self-discovery, self-reflection, self-realisation and self-exploration.