For over 200 years, Western scholars have struggled to understand Hinduism, a faith whose followers seemed (to outsiders) to arbitrarily worship any one of a dozen Gods as the Supreme, a religion vastly diverse in its beliefs, practices and ways of worship. Some Indologists labeled the Hinduism they encountered polytheistic; others even coined new terms, like henotheism, to describe this baffling array of spiritual traditions. Few, however, have realized, and fewer still have written, that India's Sanatana Dharma, or "eternal faith," known today as Hinduism and comprising over a billion followers, is a family of religions with four principal denominations--Saivism, Shaktism, Vaishnavism and Smartism. This single perception is essential for understanding Hinduisim and explaining it accurately to others. Contrary to prevailing misconceptions, Hindus all worship a one Supreme Being, though by different names. For Vaishnavites, Lord Vishnu is God. For Saivites, God is Siva. For Shaktas, Goddess Shakti is supreme. For Smartas, liberal Hindus, the choice of Deity is left to the devotee. Each has a multitude of guru lineages, religious leaders, priesthoods, sacred literature, monastic communities, schools, pilgrimage centers and tens of thousands of temples. They possess a wealth of art and architecture, philosophy and scholarship. These four sects hold such divergent beliefs that each is a complete and independent religion. Yet, they share a vast heritage of culture and belief--karma, dharma reincarnation, all-pervasive Divinity, tem­ple worship, sacraments, manifold Deities, the guru-disciple tradition and the Vedas as scriptural authority. In this fourteen-page Insight, drawn from Satguru Sivaya Subramuniyaswami's Dancing with Siva, we offer a synopsis of these four denominations, followed by a point-by-point comparison.