Here he delivered a famous speech beginning with the words: "Sisters and brothers of America ..." introducing the ancient Hindu religious tradition to Americans and speaking forcefully about the essential unity of all spiritual paths, and the necessity of embracing tolerance and renouncing fanaticism.

[12] After the great success of the Parliament, Vivekananda delivered hundreds of lectures across the United States, England, and Europe, disseminating the core tenets of Hindu philosophy.

[15][16] Vivekananda was born as Narendranath Datta (name shortened to Narendra or Naren)[18] in a Bengali Kayastha family[19][20] in his ancestral home at 3 Gourmohan Mukherjee Street in Calcutta,[21] the capital of British India, on 12 January 1863 during the Makar Sankranti festival.

[35][36] Narendra studied the works of David Hume, Immanuel Kant, Johann Gottlieb Fichte, Baruch Spinoza, Georg W. F. Hegel, Arthur Schopenhauer, Auguste Comte, John Stuart Mill and Charles Darwin.

[49] His initial beliefs were shaped by Brahmo concepts, which denounced polytheism and caste restrictions,[29][50] and proposed a "streamlined, rationalized, monotheistic theology strongly coloured by a selective and modernistic reading of the Upanisads and of the Vedanta.

[51] His ideas were "altered [...] considerably" by Debendranath Tagore, who had a romantic approach to the development of these new doctrines, and questioned central Hindu beliefs like reincarnation and karma, and rejected the authority of the Vedas.

[53] Sen was influenced by transcendentalism, an American philosophical-religious movement strongly connected with unitarianism, which emphasised personal religious experience over mere reasoning and theology.

[57] Swami Medhananda agrees that the Brahmo Samaj was a formative influence,[58] but affirms that "it was Narendra's momentous encounter with Ramakrishna that changed the course of his life by turning him away from Brahmoism.

We had no thought even as to whether the world existed or not.In 1887, Narendra compiled a Bengali song anthology named Sangeet Kalpataru with Vaishnav Charan Basak.

[88] Narendra travelled extensively in India for five years, visiting centres of learning and acquainting himself with diverse religious traditions and social patterns.

During his travels he met and stayed with Indians from all religions and walks of life: scholars, dewans, rajas, Hindus, Muslims, Christians, paraiyars (low-caste workers) and government officials.

[91] On the suggestion of his patron, friend and disciple Raja Ajit Singh of Khetri, he adopted the name "Vivekananda"–a conglomerate of the Sanskrit words: viveka and ānanda, meaning "the bliss of discerning wisdom".

[92][93] Vivekananda visited several cities in Japan (including Nagasaki, Kobe, Yokohama, Osaka, Kyoto and Tokyo),[94] China and Canada en route to the United States,[95] reaching Chicago on 30 July 1893.

[109][note 2] Vivekananda quoted two illustrative passages from the "Shiva mahimna stotram": "As the different streams having their sources in different places all mingle their water in the sea, so, O Lord, the different paths which men take, through different tendencies, various though they appear, crooked or straight, all lead to Thee!"

"[112][113] Parliament President John Henry Barrows said, "India, the Mother of religions was represented by Swami Vivekananda, the Orange-monk who exercised the most wonderful influence over his auditors".

The New York Critique wrote, "He is an orator by divine right, and his strong, intelligent face in its picturesque setting of yellow and orange was hardly less interesting than those earnest words, and the rich, rhythmical utterance he gave them".

[123] In November 1895 he met an Irish woman, Margaret Elizabeth Noble, who would become one of his closest disciples, known as Sister Nivedita (a name given her by the Swami, meaning "dedicated to God").

[129][130] Vivekananda attracted followers and admirers in the US and Europe, including Josephine MacLeod, Betty Leggett, Lady Sandwich, William James, Josiah Royce, Robert G. Ingersoll, Lord Kelvin, Harriet Monroe, Ella Wheeler Wilcox, Sarah Bernhardt, Nikola Tesla, Emma Calvé and Hermann Ludwig Ferdinand von Helmholtz.

[147] On 1 May 1897 in Calcutta, Vivekananda founded the Ramakrishna Mission, an institution dedicated to social service, with ideals based on Karma Yoga.

[153][154][155] He visited Punjab, attempting to mediate an ideological conflict between Arya Samaj (a reformist Hindu movement) and sanatan (orthodox Hindus).

After a brief stay in England, he went to the United States where he established Vedanta Societies in San Francisco and New York and founded a shanti ashrama (peace retreat) in California.

He taught Shukla-Yajur-Veda, Sanskrit grammar and the philosophy of yoga to pupils, later discussing with colleagues a planned Vedic college in the Ramakrishna Math.

[176] Influenced by Ramakrishna, he came to see the Vedanta as providing the ontological basis for śivajñāne jīver sevā – the spiritual practice of serving human beings as actual manifestations of the divine.

[note 3] According to Anil Sooklal, Vivekananda's neo-Vedanta "reconciles Dvaita or dualism and Advaita or non-dualism," viewing Brahman as "one without a second" yet both saguna (qualified) and nirguna (qualityless).

[182][note 4] According to Jackson, the Vedanta acquires a modern and Universalistic form in Vivekananda's summary, showing also the influence of classical yoga:[179] Each soul is potentially divine.

Doctrines, or dogmas, or rituals, or books, or temples, or forms, are but secondary details.Vivekananda's emphasis on nirvikalpa samadhi was preceded by medieval yogic influences on Advaita Vedanta.

[3] His reinterpretation created a new understanding and appreciation of Hinduism inside and outside India,[3] and paved the way for the enthusiastic reception of other forms of Indian spiritual self-improvement in the West, such as yoga and Transcendental Meditation.

[210] In September 2010, the then Union Finance Minister Pranab Mukherjee, who later became President of India, approved in principle the Swami Vivekananda Values Education Project at a cost of ₹1 billion (US$12 million).

The project's objectives included publishing Vivekananda's works in a number of languages, and involving youth with competitions, essays, discussions and study circles.

Since most of these lectures were delivered spontaneously and with minimal preparation, his written style often retained the variability characteristic of his speech, and could be "in turn discursive or expository, conversational or declamatory.