  Ockham's view does not go unchallenged. Walter Burley (ca. 1275–1344/5), for example, develops his mature doctrine of categories in opposition to Ockham in his Commentary on the Old Logic (Conti 1990) and influences such later medieval realists as Robert Arlyngton (fl. 1390), John Sharpe (1360-1415), and John Wyclif (1324-1384).