Abraham Harold Maslow (; April 1, 1908 - June 8, 1970) was an American psychologist who was best known for creating Maslow's hierarchy of needs, a theory of psychological health predicated on fulfilling innate human needs in priority, culminating in self-actualization. Maslow was a psychology professor at Alliant International University, Brandeis University, Brooklyn College, New School for Social Research, and Columbia University. He stressed the importance of focusing on the positive qualities in people, as opposed to treating them as a "bag of symptoms." A Review of General Psychology survey, published in 2002, ranked Maslow as the tenth most cited psychologist of the 20th century.

During the 1960s Maslow founded with Stanislav Grof, Viktor Frankl, James Fadiman, Anthony Sutich, Miles Vich and Michael Murphy, the school of transpersonal psychology. Maslow had concluded that humanistic psychology was incapable of explaining all aspects of human experience. He identified various mystical, ecstatic, or spiritual states known as "peak experiences" as experiences beyond self-actualization. Maslow called these experiences "a fourth force in psychology", which he named transpersonal psychology. Transpersonal psychology was concerned with the "empirical, scientific study of, and responsible implementation of the finding relevant to, becoming, mystical, ecstatic, and spiritual states" (Olson & Hergenhahn, 2011).  Maslow published in 1962 a collection of papers on this theme, which developed into his 1968 book Toward a Psychology of Being. In this book Maslow stresses the importance of transpersonal psychology to human beings, writing: "without the transpersonal, we get sick, violent, and nihilistic, or else hopeless and apathetic" (Olson & Hergenhahn, 2011). Human beings, he came to believe, need something bigger than themselves that they are connected to in a naturalistic sense, but not in a religious sense: Maslow himself was an atheist and found it difficult to accept religious experience as valid unless placed in a positivistic framework.  Awareness of transpersonal psychology became widespread within psychology, and the Journal of Transpersonal Psychology was founded in 1969, a year after Abraham Maslow became the president of the American Psychological Association. In the United States, transpersonal psychology encouraged recognition for non-western psychologies, philosophies, and religions, and promoted understanding of "higher states of consciousness", for instance through intense meditation. Transpersonal psychology has been applied in many areas, including transpersonal business studies.

What do the critics say about transpersonal psychology?