William of Ockham was a fourteenth century (c. 1288 – 1347) English Franciscan friar. In 1324 he was summoned by Pope John XXII to Avignon where he concluded, in a controversy over the concept of ‘apostolic property’ between his order and the papacy, that the Pope was in heresy. He subsequently fled Avignon in 1328 and lived for the rest of his life in Munich where he enjoyed the protection of the Holy Roman Emperor, Louis of Bavaria. During his exile in Munich he composed most of his political writings and died an excommunicant.
William has given his name to the concept known as Occam’s razor. The razor is frequently expressed as ‘beings (or entities) should not be multiplied beyond necessity’.
There are many forms of the razor, but they can be broadly classified as two kinds: methodological, which presumes to explain the correct method by which to select the most likely explanation of a problem or situation from a universe of otherwise attractive theories; and, metaphysical, which presumes to explain the metaphysical simplicity of the world. The principle of parsimony has a logical dual, or anti-razor: the principle of plenitude, which is the razor in its reciprocal form.
William’s concept has been applied variously throughout history to aspects of science, physics, chemistry, biology, medicine, religion, philosophy and probability theory.

Further Reading
Spade, PV. The Cambridge Companion to Ockham, Cambridge University Press 1999
Keele, R. Ockham Explained From Razor To Rebellion, Open Court Publishing Company 2010