William of Ockham (1280 - 1349)
William of Ockham (or alternately, Occam) is most well known for Ockham's Razor.
William was a Franciscan friar who believed that the absolute poverty of Christ and the apostles was a necessary ideal. This view, in opposition to the Pope led to his excommunication and imprisonment.
Because of his unpopularity, few of his works have survived in entirety. His philosophy can be described as Augustinian-Platonist, although much influenced by his teacher Duns Scotus.