Psychologists affiliated with the humanistic school reject the narrow singularities and reductionism they encounter in many of the other systems of psychology. The defiant capacity, the ability to neutralize or even transcend conditioning, is, according to the humanistic psychologist, a unique feature of human nature. The humanistic viewpoint gained momentum in the 1960s when behaviorism and psychoanalysis were dominant forces. The psychology and philosophy of William James are important in the intellectual background of humanistic psychology for several reasons. Humanistic psychology's ancestry is rooted in philosophers who devoted themselves to an understanding of the emotional, social, and intellectual issues of life. The deep and rich intellectual background of humanistic psychology is encountered in the works of scholars who emphasized the importance of inner experience, the various meanings of freedom, and the experience of intentionality and activity of mental processes. Meaning orientation, truthfulness, practicality, and personhood are central themes in the works of Unamuno, just as they are in humanistic psychology.