Hindu philosopher and social reformer who attempted to incorporate Christian theology within the framework of Hindu thought.

Although not of the Brahman caste, Sen's family was prominent in Calcutta, and he received the required education. At age 19 he joined the Brahmo Samaj (Society of Brahmā, also translated as Society of God) founded in 1828 by the Hindu religious and social reformer Rammohan Ray. The Brahmo Samaj was intended to revitalize Hindu religion through use of ancient Hindu sources and the authority of the Vedas. Sen was convinced, however, that only Christian doctrine could bring new life to Hindu society.

By the use of dynamic and practical Christian missionary methods, Sen effected social reforms that were badly needed in India; he organized relief campaigns for the poor, promoted literacy among his countrymen by founding schools for children and adults, and issued a number of inexpensive publications to bring reading matter within the reach of all. He condemned child marriage and was instrumental in having the marriage rites of his society recognized by law in 1872. He also advocated widow-remarriage and even intercaste marriage.

While his contemporaries Debendranath Tagore (Tagore, Debendranath) and Ramakrishna remained thoroughly Hindu in outlook, Sen very nearly converted completely to Christianity. The deterrent proved to be his belief that Christ, however admirable, was not unique. Nevertheless, he did want his people to emulate Christ, believing that only a vital Christianity would be the salvation of a stratified and ossified Hindu society. He was more interested in the practical application of religion to social conditions than in depth of thought. An open break with Debendranath Tagore followed, and Sen formed a new society in 1866 called the Bharatvarshiya Brahmo Samaj (“Society of Brahmā of India”). The original society was renamed the Adi Samaj (“Old Society”) and was quickly purged of Christian teaching.

In 1870 Sen lectured widely in England and was presented to Queen Victoria. Again he was impressed with Christianity as a force in English life. Back in India, however, he allowed his 14-year-old daughter to marry the son of the maharaja of Cooch Behār, thus publicly repudiating his avowed opposition to child marriage. As a result, some of his followers broke away, and he organized a new society, Naba Bidhān, or Nava Vidhāna (“New Dispensation”), continuing to preach a mixture of Hindu philosophy and Christian theology. He revived many ancient Vedic practices and sent out 12 disciples to preach under a flag bearing a crescent, a cross, and a trident. Sen retained public esteem until his death.