One of the world's most ancient religions is a force in modern Indian politics. Hinduism, the avowed faith of Prime Minister Narendra Modi, forms the philosophical bedrock of his ruling Bharatiya Janata Party (BJP). It is also the religion of 80 percent of India's nearly 1.3 billion people, making it the third-largest faith tradition globally, after Christianity and Islam. Of course, despite its overwhelming demographic presence, Hinduism never became India's official religion. Instead, India, as outlined in its constitution, has remained an officially secular nation, home to a dizzying array of philosophies and interpretations, movements and sects, and significant communities of religious-minority Muslims, Christians and Sikhs. The architects of the secular and pluralistic concept of Indian nationhood that sought to embrace this diversity were Mahatma Gandhi and Jawaharlal Nehru, India's first prime minister.