This book is an attempt to reconstruct the foundations of Indian philosophy which are reflected in early Indian texts dated between 13th and 6th B.C.E. They are religious texts composed in Sanskrit which were transmitted orally in the families of priests called Brahmins. They constitute the intellectual foundation of Indian culture called Sruti, literally, 'what has been heard'. They are generally called Veda which means 'knowledge'. The sources forming the basis for the analysis presented in this book come from three layers of the Vedic tradition. The earliest layer is the four Vedas: the Veda of Rk-stanzas (Rgveda), the Veda of Samanchants (Samveda), the Veda of Yajus-formulas (Yajurveda) and the Veda of Atharvans (Atharvaveda). The first part of this book's title refers to these three layers of ancient Indian tradition. The concept of fire is the central metaphysical concept of Rgvedic thought and remains such until the Brahmanas. The second part of the title refers to a further aim of the book, which is to present a history of ancient Indian thought.