Brahmo Samaj
In 1857 Sen again took employment in clerkship, this time as private secretary to Dwijendranath Tagore and joined the Brahmo Samaj. In 1859, Sen dedicated himself to the organisational work of the Brahmo Samaj and in 1862 was assigned, by Hemendranath Tagore, a stipendary ministry (Acharya) of one of its worship houses despite being a non-Brahmin (previously a Shudra untouchable had been made an Acharya by Debendranath Tagore).
In 1858, left his home in Coolootola and took refuge in the Jorasanko House of the Tagore family when the patriarch of the family was then away. In 1862 Sen helped found the Albert College and wrote articles for the Indian Mirror, a weekly journal of the Calcutta Brahmo Samaj in which social and moral subjects were debated.
In 1863 he wrote The Brahma Samaj Vindicated. He strongly criticized Christianity and traveled about the country lecturing and preaching that the Brahmo Samaj was intended to revitalize Hindu religion through use of ancient Hindu sources and the authority of the Vedas. By 1865, however, Sen was convinced that only Christian doctrine could bring new life to Hindu society.
In November 1865 he was caused to leave the Brahma Samaj after "an open break with its founder Debendranath Tagore" over Christian practices in Brahmoism, and the next year (1866) with encouragement of the Unitarian preacher Charles Dall he joined another new organisation BharatBarshiya Brohmo Samaj (Brohmo Samaj of India) as its Secretary (the President being "God"). Tagore's Brahmo Samaj then quickly purged itself of Sen's Christian teaching and encouraged being described as Adi Brahmo Samaj to distinguish it from Sen's deliberately eponymous version.
Read more about this topic: Keshub Chunder Sen