Ockham is most famous for using the principle of parsimony in his writings: denying universal realities, reducing the realities often associated with the categories, employing his razor wherever relevant. In its original presentation the razor or principle of parsimony was a principle enunciated by Aristotle in Books I and VII of his Physics (188a 17-18 and 259a 8-15): ‘‘Plurality must not be admitted without necessity.’’ William appealed to it in the very first question of his Prologue to Book I of the Sentences in his discussion of the distinction between intuitive and abstractive cognition (Opera theologica I, 74-75). We can see from the discussions above concerning supposition, the categories and natural philosophy that he was ridding the world of extra realities he considered unnecessary. One of his chief targets was John Duns Scotus and the metaphysical principle of haeceitas (thisness) that Scotus employed to explain the distinctness of individuals within a species. In the Summa logicae (Opera philosophica I, 772) William tells us that the proposition ‘‘The ‘thisness’ of Socrates is something’’ can be understood in two ways: it can mean that the ‘‘thisness’’, which is a thing distinct from other ‘‘thisnesses’’, is something or it can mean that Socrates who is this man or this creature or this being is something. Ockham thinks it is so evident which is correct, that he does not explicitly tell you which choice is his. If it was evident to him which was the correct choice, it was not evident to Walter Chatton. Walter, a great defender of Duns Scotus, was teaching at London with Ockham, in the years before Ockham was called to Avignon. Chatton’s challenge to Ockham was his ‘‘rule’’ or ‘‘anti-razor’’ which he formulated in this way: ‘‘If three things are not enough to verify an affirmative proposition about things, a fourth must be added, and so on.’’ In brief, he was arguing that one must not posit less than are necessary. In response, in Quodlibet VII, q. l (Opera theologica IX, 704, 17-19) Ockham casts his razor in corresponding new terms: ‘‘When a proposition is verified of things, if three or two things suffice for its truth, it is not necessary to posit a fourth,’’ etc.
World History
