In this chapter we have examined the humanistic theories of Carl Rogers and Abraham Maslow. In the next chapter we will examine the existential theories of Viktor Frankl and Rollo May. What really is the difference? The distinction is subtle, based on definition, and may seem nonexistent at first glance. Indeed, both the humanistic and existential theorists have been influenced by the likes of Adler, Horney, Fromm, and Otto Rank, and Rogers in particular often writes about existential choices in his books. Even the cognitive therapist Albert Ellis, himself profoundly influenced by Adler, considered Rational Emotive Behavior Therapy to be distinctly humanistic (see Humanistic Psychotherapy; Ellis, 1973). In 1986, the Saybrook Institute republished a series of essays, which had appeared in the Journal of Humanistic Psychology, under the title Politics and Innocence: A Humanistic Debate (May, Rogers, Maslow, et al., 1986). In this volume, Rogers refers to May as “the leading scholar of humanistic psychology.” May, for his part, concluded an open letter to Rogers in which he expressed “profound respect for you and your contribution in the past to all of us.” May also maintained a friendship and correspondence with Maslow (May, 1991). Clearly, the humanistic and existential psychologists have much in common, and the important figures here in America communicated actively and with respect for the contributions of each other.