Namit Arora at 3 Quarks Daily has also written about the fascinating Carvaka.
The historian Romila Thapar has observed that "until recently, it was generally thought that Indian philosophy had more or less bypassed materialism." But scholars now widely recognize that in ancient "spiritual India", atheistic materialism was a major force to reckon with. Predating even the Buddhists, the Carvaka is one of the earliest materialistic schools of Indian philosophy (named after one Carvaka, a great teacher of the school, with Brhaspati as its likely founder). Its other name, Lokayata, variously meant "the system which has its base in the common, profane world," "the art of sophistry," and also "the philosophy that denies that there is any world other than this one."
The Carvakas offered an epistemological justification for their materialism that echoes British empiricist and skeptic David Hume, as well as logical positivists. The Carvakas admitted sense perception alone as a means of valid knowledge, and challenged inferential knowledge on the ground that all inference requires a universal major premise (e.g., "All that possesses smoke possesses fire") but there is no way to reach certainty about such a premise. The premise may be vitiated by some unknown "condition," and we can't know that such a vitiating condition does not exist. Since inference is not a means of valid knowledge, all supersensible things like "destiny," "soul," or "afterlife," do not exist. To say that such entities exist is regarded as absurd, for no unverifiable assertion of existence is meaningful.
The Carvaka denied the authority of all scriptures. First, knowledge based on verbal testimony is inferential and so vitiated by the flaws of inference. The scriptures, they claimed, are characterized by three faults: falsity, self-contradiction, and tautology. Based on such a theory of knowledge, the Carvaka defended a complete reductive materialism according to which the four elements of earth, water, fire, and air are the only original components of being; all other forms are products of their composition. Consciousness arises from the material structure of the body and characterizes the body itself—rather than a soul—and perishes with the body. Ajita Keshakambalin, a prominent Carvaka and contemporary of the Buddha, proclaimed that humans literally go from earth to earth, ashes to ashes, dust to dust