My object in this volume is to write the history of what is called Nyaya, one of the six schools into which orthodox philosophy in India is divided. The word ëlogicí, although it is in common parlance held synonymous with Indian Nyaya, is not exactly identical with it. Logic covers some of the subjects of Nyaya as well as Vasesika and is not co-extensive with either. The author has in this work clearly marked the principal stages of Indian logic in the vast period of about two thousand years beginning from 640 and has traced how from Anviksiki the science of debate Indian logic developed into the science of knowledge Pramanasastra and then into the science of dialectics Prakarana of Tarkasastra. The treatment of the subject is both historical and critical. The author has traced some Greek influence on indian logic. For instance he has shown how the five membered syllogism of Aristotle found its way through Alexandria Syria and other countries into Taxila and got amalgamated with the Nyaya doctrine of inference. The book is one of the pioneer works on the subjects. It has drawn on original sources exhaustively. Besides the preface introduction, foreword and table of contents the work contains several appendices and indexes.