INTRODUCTION 359
philosophy from theology and reason from faith more completely than had any
of his predecessors.
Ockham is probably best known for his “Law of Parsimony,” or “Ockham’s
Razor.” This principle has often been formulated as entia non sunt multiplicanda
praeter necessitatem,“entities are not to be multiplied beyond necessity,” though
none of Ockham’s known works contains that exact phrase.* Essentially this prin-
ciple holds that we should always seek the simplest explanation, a principle still
used by philosophers and scientists. Ockham was not the first to enunciate this
principle: It can be found earlier in the writings of Thomas Aquinas,** Duns
Scotus, and even, in embryonic form, in Aristotle.*** But the skill with which
Ockham wielded this “razor” ensured its association with his name.
Ockham was especially effective in using his razor on the question of univer-
sals. Contrary to the moderate realism dominant in his day, Ockham saw no need
to posit universals as real entities beyond individual things. This critique is clear
in the selections on universals given here. Following some defining of terms,
Ockham argues against the realist position and, with great care, against the posi-
tion of the “Subtle Doctor,” Duns Scotus. Ockham asserts that “in a particular
substance there is nothing substantial except the particular form, the particular
matter, or the composite of the two”—that is, there is no real universal apart from
the particular thing.Marilyn McCord Adams’s William Ockham,two volumes (Notre Dame, IN:
University of Notre Dame Press, 1987) is the definitive introduction to Ockham,
whereas Meyrick Heath Carré,Realists and Nominalists (London: Oxford
University Press, 1946), and Sharon M. Kaye and Robert M. Martin,On
Ockham(Belmont, CA: Wadsworth, 2001) provide helpful overviews. Special-
ized studies include E.A. Moody,The Logic of William of Ockham(1935;
reprinted New York: Russell and Russell, 1965); Damascene Webering,The
Theory of Demonstration According to William Ockham(St. Bonaventure, NY:
Franciscan Institute, 1953); Herman Shapiro, Motion, Time and Place
According to William Ockham(St. Bonaventure, NY: Franciscan Institute,
1957); Arthur Stephen McGrade,The Political Thought of William of Ockham:
Personal and Institutional Principles(London: Cambridge University Press,
1974); and Rega Wood,Ockham on the Virtues(West Lafayette, IN: Purdue
University Press, 1997). For collections of essays, see Philotheus Bohner, ed.,
Collected Articles on Ockham(St. Bonaventure, NY: Franciscan Institute, 1958)
and Paul V. Spade, ed.,The Cambridge Companion to Ockham(Cambridge:
Cambridge University Press, 1999).Ockham’s extant writings do include the phrases pluralitas non est ponenda sine necessitate, “plurality
is not to be posited without necessity,” and frustra fit per plura quod potest fieri per pauciora,“what can be
explained by the assumption of fewer things is vainly explained by the assumption of more things.” Perhaps
applying his principle to its own formulation, we should say, “Why use many if few will do?”
See his Summa Theologica,Part I, Q. 2, a. 3, obj. 2—page 334 in this volume.
See Postcrior AnalyticsI.25, 86a33–35 and PhysicsI.4, 188a17–18; VIII.6, 259a8–12.