The present treatise is a critical study of the different systems of Indian Philosophy. The study is based on original sources, and its principal value lies in their interpretation. On almost all fundamental points the author has quoted from the original texts to enable the reader to compare the interpretations with the text. The book is divided into 20 chapters. It opens with the survey of Indian philosophical thought as found in the Vedas, the Upanisads and Bhagavadgita (chs. 1-2). It proceeds to the study of Materialism, Jainism and Early Buddhism (chs. 3-5), Sunyavada, Vijnanavada and Svatantra Vijnanavada (chs. 6-8). It expounds the tenets of the six systems of Indian Philosophy (chs. 9-13) with special reference to Sankara, the pre-Sankara and the post Sankara Vedanta (chs. 14-16), and the essentials of Buddhism and Vedanta in comparison and contrast ch. 17). It discusses the doctrines of Vedanta as interpreted by Ramanuja, Madhva, Nimbarka, Vallabha, Caitanya and Aurobindo (chs. 18-19). It also contains a clear exposition of Saiva Siddhanta, Kashmir Saivism and Sakta Schools (ch. 20). The work is based on author`s study of the original sources. On almost all fundamental points he has either quoted from the original texts or referred to them to enable the interested reader to compare the interpretations with the texts.