India is the cradle of two of the world's great religions, Hinduism and Buddhism. The principal texts of Hinduism—the Rig Veda ( Verses of Spiritual Knowledge ), the Upanishads ( Ways of Worship ), and the Bhagavad-Gita ( Song of the Lord )—were written between 1200 and 100 BC . The teachings of Buddha, who lived during the 6th–5th centuries BC , were first transmitted orally and then systematized for transmission throughout Asia. Jainism, a religion that developed contemporaneously with Buddhism, has largely been confined to India. The Sikh religion began in the 15th century as an attempt to reconcile Muslim and Hindu doctrine, but the Sikhs soon became a warrior sect bitterly opposed to Islam.
Freedom of worship is assured under the constitution. In 2002, an estimated 81% of the population adhered to Hinduism. Hindus have an absolute majority in all areas except Nagaland, Jammu and Kashmir, and the tribal areas of Assam. Sikhs (about 2% of the population) are concentrated in the state of Punjab, which since 1980 has been the site of violent acts by Sikh activists demanding greater autonomy from the Hindu-dominated central government. Other religious groups include Muslims (12% in 2002. mostly Sunni) and Christians (2.3%). The remaining religion followers consist of Buddhists, Jains, and other groups. Muslims comprise more than 10% of the population in Maharashtra, Bihar, Karnataka, and West Bengal, and more than 30% of the total population in Assam and Kerala. Christians form the majority in Nagaland and are a sizable minority in Kerala. The Jains are an important minority in Rajasthan and Gujarat, and the Parsis (Zoroastrians) in Maharashtra.
The caste system is a distinct feature of Hinduism, wherein every person either is born into one of four groups—Brahmans (priests and scholars), Kshatriyas (warriors and rulers), Vaisyas (shopkeepers, artisans, and farmers), and Sudras (farm laborers and menial workers)—or is casteless and thus untouchable (now known as Harijan, from the term used by Mahatma Gandhi). Within the four major castes there are 2,500 to 3,000 subcastes based upon occupation, geographic location, and other factors. Although the constitution outlaws caste distinctions and discrimination, especially those applying to untouchability, progress in changing customs has been slow.