The Yogasutra is one of the most important works of Indian culture. The present book is an attempt of interpretation of the Yogasutras based on some special criteria adopted by the authros: (1) To use the traditional commentaries as auxiliaries, not as guides, with prudence and freedom, (2) To interpret those Sutras, in which Patanjali analyzes real phenomena, as what they actually are: descriptions of facts of experience. To such an end the authors have tried to have a clear idea of the phenomena to which Patanjali refers, and in this task they have found extremely useful the descriptions of their mystical experiences by Yogis of India and Christian mystics. The book includes the Sanskrit text of the Sutras and an English translation by the authors.