Thomas de Vio Cajetan

Thomas Cajetan (pronounced Ca-'je-tan), also known as Gaetanus, commonly Tommaso de Vio or Thomas de Vio (20 February 1469 - 9 August 1534), was an Italian philosopher, theologian, cardinal (from 1517 until his death) and the Master of the Order of Preachers 1508-18. He was a leading theologian of his day who is now best known as the spokesman for Catholic opposition to the teachings of Martin Luther and the Protestant Reformation while he was the Pope's Legate in Wittenberg, and perhaps also among Catholics for his extensive commentary on the Summa Theologica of Thomas Aquinas.

De Vio was born in Gaeta, then part of the Kingdom of Naples, as Jacopo Vio. The name Tommaso was taken as a monastic name, while the surname Cajetan derives from his native city. At the age of fifteen he entered the Dominican order, and, devoting himself to studies in philosophy of St. Thomas Aquinas (he is the founder of Neothomism), became, before the age of thirty, a doctor of theology at Padua, where he was subsequently professor of metaphysics.

He is not to be confused with his contemporary, Saint Cajetan, the founder of the Theatines.