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William of Ockham (also Occam, Hockham, or any of several other spellings, Template:Pron-en) (c. 1288 - c. 1348) was an England Franciscan friar and scholastic philosopher, from a place named Ockham in Yorkshire, or possibly Surrey. He is considered — along with Thomas Aquinas, Duns Scotus, and the Islamic scholar Averroes — to be one of the major figures of medieval thought and was at the centre of the major intellectual and political controversies of the fourteenth century. Although he is commonly known for Occam's razor, the methodological principle that bears his name, William of Ockham also produced significant works on logic, physics, and theology.


File:William of Ockham - Logica - 1341.jpg

William of Ockham - Sketch labelled "frater Occham iste", from a manuscript of Ockham's Summa Logicae, 1341

William of Ockham joined the Franciscan order at a young age. He is believed to have studied theology at the University of Oxford from 1309 to 1321, but never completed his master's degree (the usual undergraduate degree in those times).[1] Because of this, he acquired the byname Venerabilis Inceptor, or "Worthy Beginner" (although he was also known as the Doctor Invincibilis or unconquerable teacher).

His work in this period became the subject of controversy, and many scholars have thought that Ockham was summoned before the Papal court of Avignon in 1324 under charges of heresy, though an alternative theory recently proposed by George Knysh suggests that he was initially appointed there as professor of philosophy in the Franciscan school, and that his disciplinary difficulties did not begin until 1327.[2] It is generally believed that these charges were levied by Oxford chancellor John Lutterell.[3] A theological commission was asked to review his Commentary on the Sentences, during which Ockham found himself involved in a different debate. The Franciscan Minister General Michael of Cesena, summoned to Avignon in 1327 to answer charges of heresy, asked Ockham to review arguments surrounding Apostolic poverty. Fundamentalist Franciscans, known as spirituals]], believed that Jesus and his apostles owned no personal property, and survived by begging and accepting the gifts of others.[4] This brought them into conflict with Pope John XXII.

After studying the works of John XXII and previous papal statements, Ockham agreed with the Minister General. He believed that John XXII was himself guilty of heresy for refusing to accept the Franciscan claim.[1] Fearing imprisonment and possible execution, Ockham, Cesena, and other Franciscan sympathizers fled Avignon on 26 May 1328, and eventually took refuge in the court of the Holy Roman Emperor Louis IV of Bavaria, who was also engaged in dispute with the papacy. Ockham was excommunicated]] for leaving Avignon, but his philosophy was never officially condemned.

He spent much of the remainder of his life writing about political issues, including the relative authority and rights of the spiritual and temporal powers. After Michael of Cesena's death in 1342, he became the leader of the small band of Franciscan dissidents living in exile with Louis IV. Ockham died (prior to the outbreak of the plague, or Black Death]]) either on 10 April 1347[5] or (more likely) on 9 April 1348 in the Franciscan convent at Munich in Bavaria[6] He was officially rehabilitated by Innocent VI in 1359.

Philosophical thought

In scholasticism, Ockham advocated a reform both in method and in content, the aim of which was simplification. Ockham incorporated much of the work of some previous theologians, especially John Duns Scotus. From Scotus, Ockham derived his view of divine omnipotence, his view of grace and justification, much of his epistemology and ethical convictions. However, he also reacted to and against Scotus in the areas of predestination, penance, his understanding of universals, his distinction ex parte rei (that is, "as applied to created things"), and his view of parsimony.


A pioneer of nominalism, some consider him the father of modern epistemology, because of his strongly argued position that only individuals exist, rather than supra-individual universals, essences, or forms, and that universals are the products of abstraction from individuals by the human mind and have no extra-mental existence.[7] He denied the real existence of metaphysical universals and advocated the reduction of ontology. Ockham is sometimes considered an advocate of conceptualism rather than nominalism, for whereas nominalists held that universals were merely names, i.e. words rather than existing realities, conceptualists held that they were mental concepts, i.e. the names were names of concepts, which do exist, although only in the mind. Therefore, the universal concept has for its object, not a reality existing in the world outside us, but an internal representation which is a product of the understanding itself and which "supposes" in the mind the things to which the mind attributes it; that is, it holds, for the time being, the place of the things which it represents. It is the term of the reflective act of the mind. Hence the universal is not a mere word, as Roscelin taught, nor a sermo, as Abelard held, namely the word as used in the sentence, but the mental substitute for real things, and the term of the reflective process. For this reason Ockham has been called a "terminist", to distinguish him from a nominalist or a conceptualist.

Over the course of his life, Ockham changed his view of what universal concepts are. To begin with, he believed that universals have no “real” existence at all in the Aristotelian categories, but instead are purely “intentional objects” more or less in the sense of modern phenomenology; they have only a kind of “thought”-reality. Such “fictive” objects were metaphysically universal; they just weren't real. Eventually, however, Ockham came to think this intentional realm of “fictive” entities was not needed, and by the time of his Summa logicae and the Quodlibets he adopted instead a so-called intellectio-theory, according to which a universal concept is just the act of thinking about several objects at once; metaphysically it is quite singular, and is “universal” only in the sense of being predicable of many.

Ontological parsimony

One important contribution that he made to modern science and modern intellectual culture was through the principle of parsimony in explanation and theory building that came to be known as Occam's Razor. This maxim, as interpreted by Bertrand Russell,[8] states that if one can explain a phenomenon without assuming this or that hypothetical entity, there is no ground for assuming it, i.e. that one should always opt for an explanation in terms of the fewest possible number of causes, factors, or variables. He turned this into a concern for ontological parsimony; the principle says that one should not multiply entities beyond necessity - Entia non sunt multiplicanda sine necessitate - although this well-known formulation of the principle is not to be found in any of Ockham's extant writings.[9] He formulates it as: “For nothing ought to be posited without a reason given, unless it is self-evident (literally, known through itself) or known by experience or proved by the authority of Sacred Scripture.” For Ockham, the only truly necessary entity is God; everything else is contingent. He thus accepts the principle of sufficient reason, rejects the distinction between essence and existence, and advocates against the Thomistic doctrine of active and passive intellect. His scepticism to which his ontological parsimony request leads appears in his doctrine that human reason can prove neither the immortality of the soul nor the existence, unity, and infinity of God. These truths, he teaches, are known to us by Revelation alone.

Natural philosophy

Ockham wrote a great deal on natural philosophy, including a long commentary on Aristotle's physics. According to the principle of ontological parsimony, he holds that we do not need to allow entities in all ten of Aristotle's categories; we thus do not need the category of quantity, as the mathematical entities are not "real". Mathematics must be applied to other categories, such as the categories of substance or qualities, thus anticipating modern scientific renaissance while violating Aristotelian prohibition of metabasis.

Ockham was arguably important in physics for his view, apparently an application of his razor, that motion is essentially self-conserving in itself without need of any causal force. This was contrary to the contemporary impetus theory of Jean Buridan that its perpetuation requires an internal force of impetus, and indeed also to Aquinas's novel theory that all bodies have an inherent resistance to motion in proportion to their mass, subsequently dubbed 'inertia' by Kepler, and also contrary to the much later view of Newton, partly derived from Parisian scholastic impetus theory, that the continuation of uniform straight motion in the absence of any resistance would be caused by an internal inherent force of inertia (vis inertiae). But it was apparently in agreement with Aristotle's view in Physics 4.8 215a19-22 that in the absence of any resistance locomotion would be interminable, apparently without need of any internal (nor external) force whatsoever, and arguably also with Descartes's principle of the conservation of motion without need of any causal force, so vehemently rejected by Newton as relativism in his De Gravitatione. In the late 19th century, the view that the continuation of unresisted uniform straight motion would not require any force whatsoever became popular amongst positivist philosophers and physicists such as Mach and Whitehead, who sought to abolish Newton's inherent force of inertia (vis inertiae) as an independent force of bodies/matter. (Mach sought to reduce it to the combined gravitational attractions of all the fixed stars, but even if so, uniform straight motion would still be caused by force in Newtonian dynamics.) But in 1878 in his book The Art of Scientific Discovery, the president of the Birmingham Scientific Society, George Gore, had (correctly) held that Newton explained planetary orbits as the resultant of the action of two forces, namely a centripetal impressed force and a transverse force of inertia inherent in each planet.

Theory of knowledge

In the theory of knowledge, Ockham rejected the scholastic theory of species, as unnecessary and not supported by experience, in favour of a theory of abstraction. This was an important development in late medieval epistemology. He also distinguished between intuitive and abstract cognition; intuitive cognition depends on the existence or non existence of the object, whereas abstractive cognition "abstracts" the object from the existence predicate. It is not yet decided among interpreters as to the role of these two types of cognitive activities.

Political theory

Ockham is also increasingly being recognized as an important contributor to the development of Western constitutional ideas, especially those of government with limited responsibility. He was one of the first medieval authors to advocate a form of church/state separation, and was important for the early development of the notion of property rights. His political ideas are regarded as "natural" or "secular", holding for a secular absolutism. The views on monarchical accountability espoused in his Dialogus (written between 1332 and 1348)[10] greatly influenced the Conciliar movement and assisted in the emergence of liberal democratic ideologies.


In logic, Ockham wrote down in words the formulae that would later be called De Morgan's Laws,[11] and he considered ternary logic, that is, a logical system with three truth values; a concept that would be taken up again in the mathematical logic of the 19th and 20th centuries.


Template:Wikisource-author The standard edition of his philosophical and theological works is William of Ockham: Opera philosophica et theologica, Gedeon Gál, et al., eds. 17 vols. St. Bonaventure, N. Y.: The Franciscan Institute, 1967-88. For his political works, all but the Dialogus have been edited in William of Ockham, H. S. Offler, et al., eds. 4 vols., 1940-97, Manchester: Manchester University Press [vols. 1-3]; Oxford: Oxford University Press [vol. 4].

Philosophical writings

  • Summa logicae (c. 1323), Paris 1448, Bologna 1498, Venice 1508, Oxford 1675.
  • Quaestiones in octo libros physicorum (before 1327), Rome 1637.
  • Summulae in octo libros physicorum (before 1327), Venice 1506.
  • Quodlibeta septem (before 1327), Paris 1487.
  • Expositio aurea super artem veterem Aristotelis, 1323.
  • Major summa logices, Venice 1521.
  • Quaestiones in quattuor libros sententiarum, Lyons, 1495.
  • Centilogium theologicum, Lyons 1495.

Theological writings

  • Questiones earumque decisiones, Lyons 1483.
  • Quodlibeta septem, Paris 1487, Strasbourg 1491.
  • Centilogium, Lyons 1494.
  • De sacramento altaris and De corpore christi, Strasbourg 1491, Venice 1516.
  • Tractatus de sacramento allans.

Political writings

  • Opus nonaginta dierum (1332), Leuven 1481, Lyons 1495.
  • Dialogus* (begun in 1332) Paris 1476. Lyons 1495.
  • Super potestate summi pontificis octo quaestionum decisiones (1344).
  • Tractatus de dogmatibus Johannis XXII papae (1333–34).
  • Epistola ad fratres minores (1334).
  • De jurisdictione imperatoris in causis matrimonialibus, Heidelberg 1598.
  • Breviloquium de potestate tyrannica (1346).
  • De imperatorum et pontifcum potestate [also known as 'Defensorium'] (1348).

See also

  • Occam's razor
  • Concept
  • History of science in the Middle Ages
  • Occam programming language
  • Oxford Franciscan school


  1. 1.0 1.1 Spade, Paul Vincent. William of Ockham. Stanford Encyclopedia of Philosophy. Stanford University. URL accessed on 2006-10-22.
  2. Knysh, George, Biographical rectifications concerning Ockham's Avignon period. Franciscan Studies 46, pp.61-91.
  3. Hundersmarck, Lawrence (1992). Great Thinkers of the Western World, 123–128, Harper Collins.
  4. McGrade, Arthur (1974). The Political Thought of William of Ockham: Personal and Institutional Principles, Cambridge University Press.
  5. Gál, Gedeon, 1982. William of Ockham Died Impenitent in April 1347. Franciscan Studies 42, pp. 90-95
  6. Knysh, George. Ockham Perspectives, Ukrainian Academy of Arts and Sciences in Canada, Winnipeg, 1994, pp. 28-29.
  7. Baird, Forrest E.; Walter Kaufmann (2008). From Plato to Derrida, Upper Saddle River, New Jersey: Pearson Prentice Hall.
  8. Russell, Bertrand (2000). History of Western Philosophy, 462–463, Allen & Unwin.
  9. W. M. Thorburn (1918). The Myth of Occam's Razor. Mind 27 (107): 345–353.
  10. Cf. the online British Academy edition at
  11. In his Summa Logicae, part II, sections 32 & 33.


  • Adams, Marilyn (1987). William Ockham, Notre Dame: University of Notre Dame Press.
  • Beckmann, Jan (1992). Ockham-Bibliographie, 1900-1990, Hamburg: F. Meiner Verlag.
  • Panaccio, Claude (2004). Ockham on Concepts, Aldershot: Ashgate.
  • Spade, Paul (1999). The Cambridge Companion to Ockham, Cambridge: Cambridge University Press.
  • Knysh, George (1996). Political Ockhamism, Winnipeg: WCU Council of Learned Societies.

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