Thomas Kelly was born into a Quaker family in Ohio in 1893. He was educated at Haverford and Harvard and acquired a reputation for outstanding scholarship. Kelly was involved in two important ministries in his early years: working with German prisoners in 1917-1918 and pastoring a Quaker community in Berlin in 1924-1925. Upon his return, he taught at Earlham College and the University of Hawaii. In 1936 he began teaching philosophy at Haverford, where he remained until his death in 1941.
While a student at Haverford, Kelly said to a professor, "I am going to make my life a miracle!" He set high standards for his life, desiring excellence in truth in all areas. Some believed that he was driven to the point of exhaustion until, in 1937, he had an experience that ended the strain and striving. His efforts were now aimed at developing an acquaintance with God, not merely acquiring knowledge about God.
Kelly was known by his colleagues as a man of genuine devotion, and his writings, in particular A Testament of Devotion and The Eternal Promise, have made a lasting impact on all who have read them. Rufus Jones said of the former book, "There are few—a very few—great devotional books...and here is a book I can recommend along with the best of the ancient ones."