Duns Scotus c. 1266 – 1308

John Duns Scotus was a 13th and early 14th-century Scottish Franciscan friar, philosopher, and theologian, regarded as one of the most important medieval scholastic philosophers alongside Aquinas and William of Ockham. Known to subsequent tradition as the Subtle Doctor for the rigour and complexity of his arguments, he developed influential positions on the univocity of being, the distinction between essence and existence, the principle of individuation through what he called haecceity or thisness, and the primacy of the will over the intellect. He defended the Immaculate Conception of the Virgin Mary against the prevailing scholastic consensus, a position that became Catholic dogma in 1854. He taught at Oxford, Paris, and Cologne and died in Cologne in 1308. The school of thought based on his work, Scotism, was a major scholastic tradition through the early modern period.