The text translated here is an historical find: an unknown commentary on the Yoga Sutra-s of Patanjali by Sankara, the most eminent philosopher of ancient India. Present Indications are that it is likely to be authentic, which would date it about AD700. The many references to meditation in his accepted works have sometimes been regarded as concessions to accepted ideas of the time , and not really his own views. If he has chosen to write a commentary on Yoga meditation, it must have been a central part of his own standpoint, although he was opposed to some of the philosophical doctrines of the official Yoga school. One would expect a tendency to modify these unacceptable doctrines if this text is really by Sankara. This turns out to be the case'. T.P.Leggett - Introduction for the general reader - 1990 '.....Leggett's translation of the Vivarana did not receive the attention it deserved when it first came out. Some of the points that he raised are well worth consideration in the context of the authorship problem, and his contribution to the debate should be recognised..... Dr Kengo Harimoto in his Foreword to the e-book edition - 2017 'When enthusiasm flags, read sutras 11.15 - 17; look around you and see how anxiety, pain and death are rushing towards us like an express train. Yoga is a way to escape them'. T.P.Leggett - How to use this book for Yoga Practice - 1990 Excerpts from 'The Complete Commentary by Sankara on the Yoga Sutra-s' by Trevor Leggett