The traditional caste system consists of a hierarchy of four castes (varnas): Brahmins (priests and teachers), Kshatriyas (rulers and warriors), Vaishyas (merchants and cultivators), and Shudras (servants). The non-Aryans who were incorporated into the Aryan society belonged to the Shudra caste. Those who were rejected on the grounds of ritual impurity were treated as and called Untouchables because members of the four castes did not associate with them. With the expansion and spread of the Hindu worldview throughout India, the division, hierarchy, and names of the traditional castes were not maintained, with the exception of the Brahmins, who claimed and were acknowledged as possessing a degree of ritual purity that retained their superiority above the other castes. The word dharma is central to Hindu belief. Hindus often refer to their religion as Hindu Dharma, basically stating that Hinduism is a way of life rather than a religion.
The key constructors and defenders of the caste system, the Brahmins, claimed that the presence of an organized caste system, with its elaborate rules and required caste duty (dharma), prevented society from degenerating into chaos. The Brahmins thus devised rules for each caste (varna) in accordance with the four stages (ashramas) in the life of a man (the Vedic society was patriarchal): celibate student, married householder, retired forest dweller, and the ascetic stage. This whole system was called varnashrama dharma— the duties of each caste in the four stages of a man's life. In the first stage, a boy receives his education by studying under a guru, and in the second stage he marries and has children. In the third stage, he retires with his wife to the forest after handing over the responsibility of the household to his oldest son. In the final stage he sends his wife home to their son and renounces all contact with the society by becoming an ascetic, and attempting to pursue moksha with greater intention. Among the four stages of the ashramas, most people only completed the first three. Retired couples usually stayed with their oldest son, and very rarely did a man become an ascetic in his old age. Basically, the concept of the four ashramas sought to synthesize the necessity of order in society and the spiritual liberation (moksha) of the individual.
With the advent and expansion of modern industries and Western education in the postindependent (after 1947) cities of India, the significance and demands of the caste system has weakened. In the major cities, a person's professional and economic status often determines his or her social standing. The secular constitution of India also outlaws untouchability and recognizes all Indian citizens as equal. Almost all urban Hindus intermingle professionally and socially, and many marry outside their caste. However, in rural areas and smaller towns, the stringent nature of the caste system and its requirements continue to define society and the lives of its members.