John Duns Scotus, a scholastic theologian of the 13th century, born probably in Dunse, Berwickshire, Scotland, about 1270, died in Cologne in 1308. He was educated at Oxford, entered the order of St. Francis, and taught theology and philosophy first at Oxford, and then, his fame having spread all over Europe, at Paris. The acumen and subtlety of his reasoning obtained for him the cognomen of doctor sub-tilis. The controversies between Duns and Thomas Aquinas on the relation of human perception to real objects, and on various religious doctrines, were continued for a long time by their respective disciples, who were called Scotists and Thomists. The reasoning of Duns goes to show that the knowledge derived from human conceptions and experience is real and trustworthy, inasmuch as the fundamental ideas upon which human knowledge rests are identical with the absolute substance (universale) of existing objects. Reality is the limitation of the absolute substance by individuation, or, in the quaint terminology of Duns, the hoecceitas, which might be rendered as the this-and-that-ity. Every existing being consists of substance and privation or limitation, while God is the unlimited absolute substance.

The possibilities of limitations or individuations of substance are infinite, and hence follows the existence of accidental chances or occurrences; and hence the free will of individual man and his corresponding responsibility to God. The supernatural knowledge which cannot be derived from real experience is afforded by the Bible, but it is the province of philosophy to show the conformity of the teachings of the Bible with reason. The works of Duns were published by Wadding (12 vols. folio, Lyons, 1639).