Book excerpt: The Svabhavikasutra is the original text on which the Bhagavadgita has been interpolated. The additions include reference to caste and the system of four classes, with a religious devotion to the god Krishna, and a war as background. The roots of the Bhagavadgita, the Svabhavikasutra, focuses on a deep spiritual philosophy, without a reference to a caste system, or to Arjuna or Krishna, or to a war.