The Book of Liberation is perhaps the most enigmatic philosophical text from ancient India. Presented as the teachings of Bhishma as he lies dying on the battlefield, after the epic war between the Pándavas and Káuravas, it was composed by unknown authors in the last centuries BCE, during the early period of world-renunciation, when peripatetic sages meditated under trees and practiced austerities in forest groves, and wandering sophists debated in the towns and cities. There has been no time like it before or since: such freedom of thought and expression is unparalleled in the history of the world.

The freedom enjoyed by these ancient thinkers was not an end in itself. Above all this animated work is the record of philosophers seeking liberation (moksha) from a world they believed unsatisfactory. The speculation herein is but a means to an end, for its authors believed they could attain freedom from the world by knowing philosophical truths.