William of Ockham
Notes
William of Ockham (c. 1287–1347), English Franciscan friar and logician. Did not invent the principle that entities should not be multiplied beyond necessity, but used it so relentlessly that it carries his name. Also excommunicated for arguing with the Pope about poverty, which is a good sign in a philosopher.
Wikipedia: https://en.wikipedia.org/wiki/William_of_Ockham