John Duns, commonly called
Duns Scotus (; 1266 – 8 November 1308), is generally considered to be one of the three most important philosopher-theologians of the
High Middle Ages. Scotus has had considerable influence on both
Catholic and secular thought. The doctrines for which he is best known are the "
univocity of being," that existence is the most abstract concept we have, applicable to everything that exists; the
formal distinction, a way of distinguishing between different aspects of the same thing; and the idea of
haecceity, the property supposed to be in each individual thing that makes it an individual. Scotus also developed a complex argument for the
existence of God, and argued for the
Immaculate Conception of
Mary.