Lokayata Darshana appears to be one of the earliest, if not the earliest, philosophical endeavour. Its authorship was ascribed to the great sage Brihaspati. The elements are earth, water, fire and air. Matter can think. There is no other world.
Death is the end of all.
Mahabharata ridicules atheists who deny the reality of soul. The Gita refers to heretics who deny the existence of God. Indian materialism was a reaction to Nihilism which propounded the doctrine that nothing existed. Sage Kanaada's Vaisheshika Darshana is frankly materialistic in its conception and exposition, according to which atoms are the cause of the world. Kapila's Saankhya is materialistic in its exposition.