This is mainly intended to give an exposition of Indian thought strictly on the basis of the original texts and commentaries. Occasionally, however, the author has sometimes discussed and borrowed the view of other writers in the assessment of chronological facts. Often the ground covered has been wholly new and the materials have been obtained by a direct and first-hand study of all available texts and manuscripts. The work appears in five volumes. Vol. I comprises Buddhist and Jaina Philosophy and the six systems of Hindu thought, viz.., Samkhya, Yoga, Nyaya, Vaisesika, Mimamsa and Vedanta.