No single creed or doctrine binds Hindus together. Intellectually there is complete freedom of belief, and one can be a monotheist (one who believes in only one god), a polytheist (one who believes in more than one god), or an atheist (one who does not believe in god). Hinduism is a syncretic religion, welcoming and incorporating a variety of outside influences. The most ancient sacred texts of the Hindu religion are written in Sanskrit and called the Vedas (vedah means “knowledge”). There are four Vedic books, of which the Rig-Veda is the oldest. It discusses multiple gods, the universe, and creation. The dates of these works are unknown (1000 B.C.?). Present-day Hindus rarely refer to these texts but do venerate them. The Upanishads (dated 1000–300 B.C.), commentaries on the Vedic texts, speculate on the origin of the universe and the nature of deity, and atman (the individual soul) and its relationship to Brahman (the universal soul). They introduce the doctrine of karma and recommend meditation and the practice of yoga. Hinduism is based on the concept of reincarnation, in which all living beings, from plants below to gods above, are caught in a cosmic cycle of becoming and perishing. Life is determined by the laws of karma, according to which rebirth is dependent on moral behavior in a previous phase of existence. In this view, life on earth is regarded as transient and a burden. The goal of existence is liberation from the cycle of rebirth and death and entrance into the indescribable state of what in Hindu texts is called moksha (liberation). The practice of Hinduism consists of rites and ceremonies centering on the main socioreligious occasions of birth, marriage, and death. There are many Hindu temples, which are dwelling places of the deities and to which people bring offerings. There are also places of pilgrimage, the chief one being Benares on the Ganges, most sacred among the rivers in India. Orthodox Hindu society in India was divided into four major hereditary classes: (1) the Brahmin (priestly and learned class); (2) the Kshatriya (military, professional, ruling, and governing occupations); (3) the Vaishya (landowners, merchants, and business occupations); and (4) the Sudra (artisans, laborers, and peasants). Below the Sudra was a fifth group, the Untouchables (lowest menial occupations and no social standing). The Indian government banned discrimination against the Untouchables in the constitution of India in 1950. Observance of class and caste distinctions varies throughout India. In modern times work has been done to reform and revive Hinduism. One of the outstanding reformers was Ramakrishna (1836–86), who inspired many followers, one of whom founded the Ramakrishna mission. The mission is active both in India and in other countries and is known for its scholarly and humanitarian works.