William of Ockham's Razor and the Rejection of Realist Universals

William of Ockham (c. 1287–1347), an English Franciscan friar educated and later teaching at Oxford, never completed the formal requirements for a doctorate in theology, which earned him the nickname "Venerabilis Inceptor," the Venerable Beginner. His major logical and philosophical works, above all the Summa Logicae (composed around 1323) and his commentary on Peter Lombard's Sentences, delivered at Oxford between roughly 1317 and 1319 and later reworked as the Ordinatio for Book I and the Reportatio for Books II–IV, established him as the most systematic and influential nominalist thinker of the fourteenth century. The methodological principle now known as Ockham's Razor, though never phrased by him in the later Latin tag "Entia non sunt multiplicanda praeter necessitatem," corresponds closely to statements he does make, such as "Frustra fit per plura quod potest fieri per pauciora" ("it is pointless to do with more what can be done with fewer") and "Pluralitas non est ponenda sine necessitate" ("plurality should not be posited without necessity"). For Ockham this was not a mere stylistic preference but a metaphysical commitment: any entity whose existence cannot be established either by direct experience or by strict logical demonstration from revealed premises should be eliminated from a philosophical account of reality.