William of Ockham was a medieval English philosopher and theologian (he was born about 1285, perhaps as late as 1288, and died in 1347 or 1348). In 1328 Ockham turned away from 'pure' philosophy and theology to polemic. From that year until the end of his life he worked to overthrow what he saw as the tyranny of Pope John XXII (1316-1334) and of his successors Popes Benedict XII (1334-1342) and Clement VI (1342-1352). This campaign led him into questions...