Wood and polychrome
Altarpiece of San Fermín, ambulatory of the Cathedral of St. Mary, Pamplona

Thomas Aquinas was a Dominican. The same altarpiece also has a santo of St. Dominic in the same roseate garment, though under a black mantle. Aquinas is sometimes shown trampling a turbaned enemy representing theological error. While I know of no other work representing him with a monstrance (the object in his left hand, used in Catholic liturgy to display the consecrated host as the body of Christ), it may be a reference to his reputation as the theological vindicator of the doctrine of transubstantiation and the author of two famous hymns sung on Corpus Christi, the feast celebrating that doctrine.

(Transubstantiation is the doctrine that in the Catholic and Orthodox liturgies, the "substance" of the bread and wine becomes the body and blood of Jesus Christ, even though these elements retain the "accidents" -- look, taste, texture, etc. -- of bread and wine.)

More of St. Thomas Aquinas