Namit Arora in the excellent 3 Quarks Daily:
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.