It is known that John Duns, the Scot, was ordained in 1291, but his earlier life is largely uncertain. He lectured in Cambridge and Oxford, then Paris, where he became regent master of theology, and he died in Cologne. His early death interrupted the production of his commentary on the Sentences of Peter Lombard. Scotus was primarily a metaphysician concerned with the nature and reality of God, with such transcendental categories as being, existence, the one, the true, and the good, and with the relations between such notions as causation, matter and form, dependency, and finitude. Amongst his preoccupations was that of the principle of individuation or distinctness, separating one horse from other horses, or me from other men. Scotus supplements the traditional Aristotelian kinds with a haecceitas or ‘thisness’: a uniquely individuating concept under which only one object falls. Scotus was a realist about universals, and his emphasis on the unique individual and its importance in metaphysics and knowledge is reflected in ethics in the primacy he accords to individual freedom, again in reaction to a fatalistic view of the problem of God’s omnipotence and foreknowledge. Like Anselm, Scotus locates freedom in our ability to turn from desire and towards justice. Scotus has been admired by such different thinkers as Peirce and Heidegger; he was dubbed the doctor subtilis, but as applied to his followers the word ‘dunce’ (short for Dunsman) reflects the low esteem into which scholasticism later fell amongst humanists and reformers.