The present treatise is a critical study of different systems of Indian Philosophy 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 opens with the survey of Indian philosophical thought as found in the Vedas, the Upanisads and Bhagavadgita. It proceeds to the study of Materialism, Jainism and Early Buddhism, Sunyavada, Vijnanavada and Svatantra Vijnanavada. It expounds the tenets of the six systems of Indian Philosophy with special reference to Sankara, the pre-Sankara and the post-Sankara Vedanta, and the essentials of Buddhism and Vedanta in comparison and contrast. It discusses the doctrines of Vedanta as interpreted by Ramanuja, Madhva, Nimbarka, Vallabha, Caitanya and Aurobindo. It also contains a clear exposition of Saiva Siddhanta, Kashmir Saivism and Sakta Schools.