Volume Four of The Collected Works of Ken Wilber includes:

- Integral Psychology, a concise version of Wilber's long-awaited textbook of transpersonal psychology, presenting one of the first truly integrative models of consciousness, psychology, and therapy.
- Charts correlating over one hundred developmental and evolutionary theories, ranging from ancient mystical traditions to modern theorists.
- Essays on human development, art, meditation, spirituality, yoga, women's studies, death and rebirth, science and mysticism, and transpersonal psychotherapies.
- Wilber's thoughtful replies to criticisms of his work.