Did Ockham Use His Razor?

DID OCKHAM USE HIS RAZOR? In the philosophical literature of the nineteenth and early twentieth centuries, the dictum called Ockham's razor that entities must not be multiplied without necessity1 is attributed to William of Ockham, the fourteenth century Franciscan philosopher.2 This principle is thought by some (Hamilton and perhaps Mill) to embody the Aristotelian dicta that God and Nature never operate without effect; they never operate superfluously. Ockham's razor is thought to be a metaphysical principle; it is an expression of the belief that the facts of the world are themselves simple (perhaps because God created the world from first principles). If we are to discover these facts, we must keep our hypotheses simple. The simpler the hypothesis, the more likely it is to correspond with the facts. We shall refer to principles which are based on the simplicity of the world as metaphysical principles . (Metaphysical principles are to be contrasted to methodological principles which are prescriptive principles of explanation independent from beliefs about the simplicity of the world). Ockham's razor as interpreted in this fashion is what Bertrand Russell refers to when he states "Ockham's razor in its original form was metaphysical , it was a principle of parsimony as regards 'entities.' I still thought of it in this way while Principia Mathematica was being written."8 1 Ockham is reputed to have stated "entia non sunt multiplicanda praeter necessitatem." — I wish to thank Girard J. Etzkorn for his numerous suggestions and corrections pertaining to this article. 2 "The above extrusion of permanent things affords as an example of the maxim which inspires all scientific philosophizing, namely, Ockham's razor': Entities must not be multiplied without necessity. In other words, in dealing with any subject matter, find out what entities are undeniably involved and state everything in terms of these entities." Bertrand Russell, Our Knowledge of the External World, George Allen & Unwin Ltd. (London, 1924), p. 112. See also Sir William Hamilton, Discussions on Philosophy and Literature, Education and University Reform, Longmans, Brown, Green and Longmans (Edinburgh, 1953), p. 629 f., or Charles Sanders Peirce, "Logic and Mathematics," The Collected Works of Charles Sanders Peirce, Vol. IV (Harvard, i960), p. 25. 8 Bertrand Russell, "My Mental Development," Library of Living Phi- ROGER ARIEW By about 1915, due to a couple of articles by W. M. Thorburn in Mind,* most philosophers when referring to the razor are found to utter some suitable apologetic words about the attribution of the razor to Ockham.6 It would seem that Ockham did not articulate "entities must not be multiplied without necessity." Mr. Thorburn attributes the dictum to the Scotist commentator, John Ponce of Cork. This would place its formulation in the seventeenth century, three centuries after Ockham. However, because of the recent work of H. S. Matsen on Alessandro Achillini, a renaissance Ockhamist, we can predate Thorburn by more than a century.6 This attribution is closer to Ockham, both temporally and philosophically. Those scholars who deny that Ockham authored Ockham's razor do not deny that Ockham held such principles as "pluralities ought not be supposed without necessity"7 and "in vain we do by many that which can be done by means of fewer."8 What they deny is that losophers, ed. P. A. Schilpp, George Bouton Publishing Co. (Menasha, Wise, 1944) p. 14. 4 W. M. Thorburn, "Occam's Razor," Mind, n.s. 24 (1915), 287-288, and "The Myth of Occam's Razor," Mind, n.s. 27 (1918), 345-353. Also C. Delisle Burns, "Occam's Razor," Mind, n.s. 24 (1915), 592. 5 "Occam is best known for a maxim which is not to be found in his works, but has acquired the name of "Occam's Razor." This maxim says: "Entities are not to be multiplied without necessity." Although he did not say this, he said something which has much the same effect, namely: "It is vain to do with more what can be done with fewer." Bertrand Russell, The History of Western Philosophy, Simon & Schuster (N.Y., 1945) p. 472. See also John Laird, "The Law of Parsimony," The Monist, vol. 29 (1919), p. 321, or Harold Jeffreys, The Theory of Probability, The...