The Cārvāka school of philosophy had a variety of atheistic, materialistic, and naturalistic beliefs.
6th century BC
No life after death
The Carvaka believed there was no afterlife, no life after death
Springing forth from these elements itself
solid knowledge is destroyed
when they are destroyed—
after death no intelligence remains.
The Carvaka believed in a form of naturalism, that is that all things happen by nature, and come from nature (not from any deity or Supreme Being).
Fire is hot, water cold,
refreshingly cool is the breeze of morning;
By whom came this variety?
They were born of their own nature.
Unlike many of the Indian philosophies of the time, The Carvaka believed there was nothing wrong with sensual indulgence, and that it was the only enjoyment to be pursued.
That the pleasure arising to man
from contact with sensible objects,
is to be relinquished because accompanied by pain—
such is the reasoning of fools.
The kernels of the paddy, rich with finest white grains,
What man, seeking his own true interest,
would fling them away
because of a covering of husk and dust?
While life remains, let a man live happily,
let him feed on butter though he runs in debt;
When once the body becomes ashes,
how can it ever return again?
Religion is invented by man
The Carvaka believed that religion was invented and made up by men, having no divine authority.
The three authors of the Vedas were buffoons, knaves, and demons.
All the well-known formulae of the pandits, jarphari, turphari, etc.
and all the obscene rites for the queen commanded in Aswamedha,
these were invented by buffoons, and so all the various kinds of presents to the priests,
while the eating of flesh was similarly commanded by night-prowling demons.
Madhavacharya and Cārvāka
Madhavacharya, the 13th & 14th-century Vedantic philosopher from South India starts his famous work The Sarva-darsana-sangraha with a chapter on the Cārvāka system with the intention of refuting it. After invoking, in the Prologue of the book, the Hindu gods Shiva and Vishnu, ("by whom the earth and rest were produced"), Madhavacharya asks, in the first chapter:
...but how can we attribute to the Divine Being the giving of supreme felicity, when such a notion has been utterly abolished by Charvaka, the crest-gem of the atheistic school, the follower of the doctrine of Brihaspati? The efforts of Charvaka are indeed hard to be eradicated, for the majority of living beings hold by the current refrain:
While life is yours, live joyously;
None can escape Death's searching eye:
When once this frame of ours they burn,
How shall it e'er again return?
Quotations attributed to Cārvāka from Sarva-Darsana-Sangraha
The Agnihotra, the three Vedas, the ascetic's three staves, and smearing oneself with ashes —
Brihaspati says, these are but means of livelihood for those who have no manliness nor sense.
In this school there are four elements, earth, water, fire and air; and from these four elements alone is intelligence produced — just like the intoxicating power from kinwa, mixed together;
since in "I am fat", "I am lean", these attributes abide in the same subject, and since fatness, &c, reside only in the body, it alone is the soul and no other, and such phrases as "my body" are only significant metaphorically.
If a beast slain in the Jyothishtoma rite will itself go to heaven, why then does not the sacrificer forthwith offer his own father?
If the Sraddha produces gratification to beings who are dead, then why not give food down below to those who are standing on the house-top?
If he who departs from the body goes to another world, how is it that he come not back again, restless for love of his kindred?
Hence it is only as a means of livelihood that Brahmans have established here all these ceremonies for the dead, — there is no other fruit anywhere.
The three authors of the Vedas were buffoons, knaves, and demons. All the well-known formulae of the pandits, jarphari, turphari, etc. and all the obscene rites for the queen commanded in Aswamedha,
these were invented by buffoons, and so all the various kinds of presents to the priests, while the eating of flesh was similarly commanded by night-prowling demons.
Those parts which survive indicate a strong anti-clerical bias, accusing Brahmins of fostering religious beliefs only so they could obtain a livelihood. The proper aim of a Charvakan or Charvaka, according to these sources, was to live a prosperous, happy, and productive life in this world.