Dr. Viktor E. Frankl is celebrated as the founder of logotherapy, a revolutionary mode of psychotherapy based on the essential human need to search for meaning in life. Even while suffering the degradation and misery of Nazi concentration camps—an experience he described in his bestselling memoir, Man's Search for Meaning—Frankl retained his belief that the most important freedom is the ability to determine one's spiritual well-being. After his liberation, he published The Doctor and the Soul, the first book in which he explained his method and his conviction that the fundamental human motivation is neither sex (as in Freud) nor the need to be appreciated by society (as in Adler), but the desire to live a purposeful life. Frankl's work represented a major contribution to the field of psychotherapy, and The Doctor and the Soul is essential to understanding it.