Brhaspati Laukya was the author of the Barhaspatya-sutras. As this work is no longer extant, it is difficult to have a clear picture of the Brhaspati Laukya’s thoughts. To learn about the Charvaka philosophy we have to rely exclusively on the presentations made by the School’s avowed opponents, most of whom were deeply religious.
Ancient texts such as Brhadaranyaka Upanisad, Katha Upanisad, Bhahma-Sutra, Vatsayayana’s Kamasutra, Kautilya’s Arthasastra, Manu Smrti, and few others have references to the Charvaka thought. But ideological opponents are seldom free of prejudices and personal predilections. They are inclined towards highlighting the negative aspects, while ignoring the positive. Therefore it shouldn't come as surprise that most of the references are derogatory.
The religious texts condemn Brhaspati Laukya for questioning the authority of the religious elders and making destructive criticism of the gods. Brhaspati rejected the idea of god—he believed that god was a product of human imagination. The references also allege that the Charvaka School made no attempt to develop a complete system of thought, their entire focus being on refuting the orthodoxy of others.
But from these references we can draw the inference that the Charvakas took an empirical, scientific, and naturalistic approach to metaphysics. They believed that metaphysical enquiry cannot be extended beyond matter, and all knowledge comes from sensory experience.
Of the recognized means of knowledge (pramana), the Charvakas recognized only direct perception (anubhava). The School held that inference can be either right or wrong, and therefore it cannot be relied to provide knowledge. Unless a direct relationship is established between perception and object or phenomenon, certainty is not possible.
According to the Charvakas, consciousness does not accrue to the particles of matter; it is only when the particles get arranged in a particular manner that life is created. The School rejected the theory of eternal soul. If there is a soul, then it goes out of existence at the time when the body dies.
By denying the idea of a soul passing from one body to another, the Charvakas rejected the popular religious notion that the religious merits or demerits that are acquired during the present birth will lead to improvements or failures in the next birth.
They rejected the idea of there being a god who is omnipotent and has the power to judge our actions. The Charvakas argued that if a judgemental and omnipotent god existed, partiality and cruelty on his part would become inevitable. Hence it is better to live in a world without god, rather than have a cruel and partial god.
The Charvakas also argued that if an omnipotent god existed we would have found a way of perceiving him through our senses. Since we can’t perceive god through our senses, he does not exist. The School asserted that instead of running after an imaginary god, people should focus on improving their earthly existence.
The Charvakas were against the priestly class. They believed that the priests were, in most cases, the sole beneficiaries of the elaborate religious rituals in which offerings are made in the name of gods. They also argued that only those individuals who are devoid of intellect and manliness tend to oblige the priests by practicing such religious rituals.
The concept of egoism has a central role to play in the Charvaka philosophy of materialism. The School has preached that every individual must give priority to fulfilling his own needs rather than using his resources to fulfil the needs of others. Charvakas believed that there is nothing wrong with sensual pleasure and they advised their followers to avoid pain and pursue pleasure.