Born Narendranath Dutta, in Kolkata in India he became famous as Swami Vivekananda, when he became the chief disciple of Shri Ramakrishna. But Vivekananda is also renowned as a thinker in his own right. One of his most important contributions was to demonstrate how Advaitin thinking is not merely philosophically far-reaching, but how it also has social, even political, consequences. One important lesson he claimed to receive from Ramakrishna was that "Jiva is Shiva " (each individual is divinity itself). This became his Mantra, and he coined the concept of daridra narayana seva - the service of God in and through (poor)human beings. If there truly is the unity of Brahman underlying all phenomena, then on what basis do we regard ourselves as better or worse, or even as better-off or worse-off, than others? - This was the question he posed to himself. Ultimately, he concluded that these distinctions fade into nothingness in the light of the oneness that the devotee experiences in Moksha. What arises then is compassion for those "individuals" who remain unaware of this oneness and a determination to help them.
Swami Vivekananda belonged to that branch of Vedanta that held that no-one can be truly free until all of us are. Even the desire for personal salvation has to be given up, and only tireless work for the salvation of others is the true mark of the enlightened person.
However, Vivekananda also pleaded for a strict separation between "church and state". Although social customs had been formed in the past with religious sanction, it was not now the business of religion to interfere with matters such as marriage, inheritance and so on. The ideal society would be a mixture of Brahmin knowledge, Kshatriya culture, Vaisya efficiency and the egalitarian Shudra ethos. Domination by any one led to different sorts of lopsided societies. Vivekananda was a socialist at heart, but he did not feel that religion should be used forcefully to bring about an ideal socialist society, since this was something that would evolve naturally by individualistic change when the conditions were right.
Vivekananda is best remembered as the man who "stole the show" at the 1893 World Parliament of Religions in Chicago, where he earned wild applause for beginning his address with the famous words, "Brothers and sisters of America." This event marks the beginning of western interest in Hinduism not as merely an exotic eastern oddity, but as a vital religious and philosophical tradition that might actually have something important to teach the west. Within a few years of the Parliament, he had started Vedantic centres in New York and London, lectured at major universities and generally kindled western interest in Hinduism. After this, he returned to India, where he died. He was only 39 years old.