Francis E. Abbot (1836-1903) was born in Boston, Massachusetts, and died in Beverly, Massachusetts. He was a Unitarian minister, philosopher, and theologian who sought to integrate theology and the scientific method. He married Katharine "Katie" Fearing Loring in 1859. Abbot earned a B.A. at Harvard University in 1859 and graduated from Meadville Theological Seminary in Pennsylvania in 1863. It was at Meadville that Abbot, confronting the theory of evolution proposed by Charles Darwin, began to question his Unitarian faith. As a result of studying Darwin, Abbot decided to dedicate himself to a lifelong goal of anchoring religious faith to science and philosophy rather than to revelation. Abbot founded the Free Religious Association in 1867. He served Unitarian churches in Dover, New Hampshire, but his ministry proved controversial as Abbot's radical religious views ruptured his relationship with his congregation, and in 1868 he resigned his position. He then briefly served as minister to a small breakaway group, the Independent Religious Society, and later accepted a position as minister of the Unitarian Society of Toledo, Ohio, which, at his insistence, severed its connection with Unitarianism. However, this society was not successful, and Abbot left it in 1873, signifying the end of Abbot's active participation in the Unitarian ministry. He was editor of The Index, a weekly publication dedicated to the advancement of Free Religion and secularism, from 1870-1880, and was organizer and President of the National Liberal League. Abbot received a Ph.D and A.M. from Harvard University in 1881 and briefly taught philosophy there in 1887. In 1893, Abbot's wife, Katie, died. Abbot was devastated by this sudden loss and spent the last ten years of his life writing of Katie and composing his final work, The Syllogistic Philosophy or Prolegomena to Science, which was finished in 1903.

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