Although materialist schools existed before Charvaka, it was the only school which systematised materialist philosophy by setting them down in the form of aphorisms in the 6th century BCE.
Charvaka holds direct perception/ empiricism and conditional inference as proper source of knowledge, embrace philosophical skepticism and rejects ritualism and supernaturalism.
Charvaka School rejects supernatural concepts like God and soul and also metaphysical concepts like afterlife (or reincarnation) and moksha.
One of the widely studies principle of Charvaka philosophy was the rejection of inference as a means to establish valid, universal knowledge, and metaphysical truths. (The Charvaka epistemology states that whenever one infers a truth from a set of observations or truths, one must acknowledge doubt; inferred knowledge is conditional).
Example of Fire and Smoke, as Smoke can have other causes also. (In Charvaka epistemology, as long as the relation between two phenomena, or observation and truth, has not been proven as unconditional, it is an uncertain truth).
They held perception and direct experiments to be the valid and reliable source of knowledge.
In Charvaka Philosophy, Perception is of 2 types – External and Internal.
External perception is described as that arising from the interaction of five senses and worldly objects, while internal perception is described by this school as that of inner sense, the mind.
Charvakas further state that full knowledge is reached when we know all observations, all premises and all conditions. But the absence of conditions, state Charvakas, can not be established beyond doubt by perception, as some conditions may be hidden or escape our ability to observe, and thus Pratyaksha (Perception) is the only valid way to knowledge and other means of knowledge are wither always conditional or invalid.
Charvaka believed that there was nothing wrong with sensual pleasure. Since it is impossible to have pleasure without pain, Charvaka thought that wisdom lay in enjoying pleasure and avoiding pain as far as possible.
The Charvakas pointed out the disagreements, debates and mutual rejection by karmakanda Vedic priests and jñānakanda Vedic priests, as proof that either one of them is wrong or both are wrong, as both cannot be right, They also held the belief that Vedas were invented by man, and had no divine authority.
Charvakas rejected the need for ethics or morals, and suggested that “while life remains, let a man live happily, let him feed on ghee even though he runs in debt”.