The Bhagavad Gita is a self-contained episode in the great Indian Sanskrit epic, the Mahabharata. The nature of its authorship and the means by which it acquired its present form are uncertain, although from internal evidence it is attributed, like the rest of the epic, to the prototypical seer, Vyasa. It may have been added to the Mahabharata or expanded out of it in approximately the third century BCE. It deals with questions of social and religious duty, the nature of action, freedom of choice, routes to spiritual liberation, and the relationship of human beings to God in a period of uncertainty and transition. From early in its history the Bhagavad Gita was an important focus for commentators, and later it became a source text for devotional movements.