Wisdom schools and mystics throughout history have reported on the human ability to expand consciousness, as our everyday perception is merely one form of reality. Transpersonal psychology systematically deals with altered states of consciousness and describes how unknown dimensions of the human soul can be discovered through this. In this book, Sylvester Walch presents his own concept of transpersonal psychology, drawing on the work of Stanislav Grof, and introduces the technique of holotropic breathing. This technique is used therapeutically to induce altered states of consciousness, which provide access to repressed content, birth experiences, prenatal states, and the mystical dimensions of the soul. Additionally, fundamental concepts of transpersonal psychology are also explained.