Saint Thomas Aquinas

Carlo Crivelli, Demidoff Altarpiece (detail of Saint Thomas Aquinas), 1476, tempera on poplar, 60.5 x 39.5 cm, National Gallery of Art, London

Thomas Aquinas was a thirteenth-century Dominican friar.  He is known for his writings called the Summa theologica, which became the scinetific, philosophical, and theoligcal foundation of Christian doctrine.  

Other attributes not seen here include the dove of inspiration, the pen symbolizing his writing, and an ox, alluding to his nickname, "the dumb ox."