The city of Varanasi is the holiest site in the Hindu faith. It is also, not coincidentally, the parliamentary constituency of Modi, who has just won a second five-year term. He did it, in large measure, by emphasizing Hindutva, an ideology that seeks to reformulate Hinduism into something that most practitioners’ grandparents would barely understand.

Religions change—that’s as timeless as time. But the transformation currently under way in Hinduism is among the most significant in modern history. It has much in common with similar changes taking place in Islam, Buddhism, and Christianity: Why are so many radical Islamists poorly versed in the Koran? How can Buddhist monks sworn to nonviolence lead pogroms in Myanmar and Sri Lanka? Why do evangelical Christians care so much about issues never mentioned by Jesus, such as abortion and homosexuality? The answer is not always hypocrisy. For many today, religion is less a matter of what you believe, or even what you do, than of who you are.

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The term Hindutva can be (sort of) translated as “Hindu-ness,” and that gets (sort of) at what it’s all about: Hinduism not a theology, but an identity. The movement’s intellectual father, Veer Savarkar, wrote its foundational text (helpfully titled Hindutva) a century ago. At the time, the notion of a unified faith or doctrine, let alone a shared identity, would have left most Hindus simply confused: Identity was determined by a person’s family, village, caste. The very term Hindu is merely a loanword (most likely from Persian), referring to “the people who live across the Indus River.” Until the 20th century, most Hindus had never felt the need to describe themselves in any comprehensive way.

It was the colonial experience that created Hindutva: Why, Savarkar and his comrades wondered, had India been dominated for centuries by a relatively small number of Muslim Mughals and Christian British? Was monotheism simply better suited for ruling? If so, what did that mean for a faith with more deities than days in the year? During the founding decades of the Hindutva movement, much effort revolved around making Hinduism more like its rivals: building a single shared identity to unite everyone for whom India was, in Savarkar’s words, “his Fatherland as well as his Holy-land.” This definition conveniently roped in Sikhs (a disproportionate number of whom served in the army), Buddhists (whose spiritual cachet helped give the movement credibility), and Jains (who tended, then and now, to be quite rich).

What it pointedly did not do was dictate what this newly lumped-together group of people should believe. Indeed, very few of Hindutva’s leading lights have been holy men, or even particularly devout; Savarkar and K. B. Hedgewar (the founder of the Rashtriya Swayamsevak Sangh, or RSS—the primary vehicle for Hindutva mobilization) are both described as having been atheists or agnostics. The point wasn’t doctrine, but branding.