The 2014 election of Prime Minister Narendra Modi and his B.J.P. emboldened every variety of Hindu nationalist group. The primary aim of these groups is an aggressive form of nationalism. But there is a contradiction at the heart of this ideology: As Mr. Paz wrote in 1995, the idea of the nation itself is “incompatible with the institution of caste.” It was not possible to want everyone to be homogeneous while at the same time believing them to be fundamentally unequal.

The contradiction presented by caste and nationalism was never clearer than in the searing images that emerged from Mr. Modi’s own home state, Gujarat, in July. They showed Dalit boys being stripped and beaten with iron rods. They were accused of killing a sacred Indian cow. But they claimed they were only skinning a cow that was already dead, work that is typically reserved for people of low caste. The irony could not have been more stark: It was caste on one hand that had forced this occupation upon them, and it was caste that was degrading them further.

Modernity should be the natural enemy of caste. And, in many ways, it is. Urban life, apartment buildings, restaurants — even something as simple as municipal water and housing — have the power to erase the prohibitions under which caste functions. Democracy, too, is an enemy of caste: The low-caste groups form a powerful voting bloc, and so politicians are obliged to be responsive to them. But by upsetting hierarchies, modernity can also exacerbate old tensions. It can make the higher castes, whose numbers are small, insecure about their place in the world and drive them to reinforce it.

The spread of modernity in India has certainly undermined caste, but it has also made the need to assert it more vehement. And the unfolding story in India is not one about the disappearance of caste, but rather of its resilience. Brahmins still have an outsize presence in intellectual life; the armed forces are still dominated by the martial castes; a majority of rich businessmen and industrialists are still of the mercantile castes; the lower castes still do the least desirable jobs.

In the cloistered, English-speaking world where I grew up, caste seemed hardly to exist. As a child in Delhi, I could no more tell a Brahmin name like Mishra or Sharma from any other. And even if I could, I would not have held it in regard. Our only category was class, and it was determined by privilege, education and how well one spoke English. But there are some categories so deep that they hold without needing to be enforced. What I didn’t realize was that in one very important respect, caste did exist among us: because the lowest castes were not represented.

For the last two years, I have been speaking with a Brahmin from Bengal, a philosopher and a teacher of ancient logic, a man conversant with both Eastern and Western intellectual traditions. I admire him in many ways — his immense learning, his defense of tradition in the face of Western influence — but when I questioned him about the prohibitions of caste he gave me an answer that turned my stomach.

“If a person is suffering from a communicable disease, you would not let him touch your utensils,” he said. “You have this one idea of contamination, but you refuse to accept that there might be certain spiritual conditions …” His voice trailed off. He seemed to know that he had lost me. As if wanting to clear the air, he said: “You have to understand that modern European culture is based on the idea that all men are born equal, and later become differentiated. The Indian idea is different. We believe that men are born unequal, but we are all — Brahmin, sage, cobbler, outcaste — heading toward the same destiny.”

It was a valiant attempt at a defense, but in the end absurd. It would mean that millions of lower-caste Indians, like Rohith Vemula, had to forfeit the aspirations of this life in exchange for the promise of some ultimate destiny, many lifetimes away, in which all differences would be obliterated.