{{Short description|English Franciscan friar and theologian (c. 1287–1347)}}
{{Infobox philosopher
| region           = [[Western philosophy]]
| era              = [[Medieval philosophy]]
| image            = William of Ockham.png
| caption          = William of Ockham depicted on a stained glass window by [[Lawrence Lee]] at [[All Saints' Church, Ockham]]<ref name="Brunton 2022 p. 425">{{cite book |last=Brunton |first=J. |title=Rogues, Rebels and Mavericks of the Middle Ages |publisher=Amberley |year=2022 |isbn=978-1-3981-0441-9 |url=https://books.google.com/books?id=PdxzEAAAQBAJ&pg=PT425 |access-date=2023-06-16 |page=425}}</ref>
| name             = William of Ockham
| honorific_suffix = [[Order of Friars Minor|OFM]]
| birth_date       = {{circa|1287}}<ref name="Larsen2011" />
| birth_place      = [[Ockham, Surrey]], England
| death_date       = 9/10 April 1347<ref name="Gedeon1982" />
| death_place      = [[Munich]], [[Duchy of Bavaria]], [[Holy Roman Empire]]
| school_tradition = {{ubl|[[Scholasticism]]|[[Occamism]]|[[Medieval nominalism|Nominalism]]{{efn|However, Ockham has also been interpreted as a defender of [[conceptualism]].}}|[[Medieval theological voluntarism|Theological voluntarism]]<ref>Walker, L. (1912). [https://www.newadvent.org/cathen/15505a.htm "Voluntarism"]. In ''[[Catholic Encyclopedia]]''. New York: Robert Appleton Company. Retrieved 27 September 2019 from [[New Advent]].</ref>}}
| education        = [[Greyfriars, London]]<ref>Spade, Paul Vincent (ed.). ''The Cambridge Companion to Ockham''. Cambridge University Press, 1999, p. 18.</ref><br>[[University of Oxford]]<ref name=Spade20>Spade, Paul Vincent (ed.). ''The Cambridge Companion to Ockham''. Cambridge University Press, 1999, p. 20.</ref><ref name=Merton/>
| notable_works    = ''[[Sum of Logic]]''
| main_interests   = 
{{flatlist|
*[[Natural philosophy]]
*[[metaphysics]]
*[[epistemology]]
*[[theology]]
*[[logic]]
*[[ontology]]
*[[politics]]
*[[Theological voluntarism]]
}}
|Albert of Saxony]], [[Jean Buridan]],<ref>Jaegwon Kim, Ernest Sosa, Gary S. Rosenkrantz (eds.), ''A Companion to Metaphysics'', Wiley-Blackwell, 2009, p. 164: "Buridan, Jean."</ref> [[Adam de Wodeham]],<ref>[[Sum of Logic|''Summa Logicae'' (c. 1323)]], [http://www.pvspade.com/Logic/docs/ockham.pdf Prefatory Letter, as translated by Paul Vincent Spade (1995)].</ref> [[Gregory of Rimini]], [[John Wycliffe]], [[Gabriel Biel]], [[Martin Luther]], [[Henry VIII]], [[John Calvin]], [[Thomas Hobbes]], [[René Descartes]], [[Edmund Burke]], [[Joseph De Maistre]], [[Bertrand Russell]]
| notable_ideas    = {{ubl|[[Occam's razor]]|[[Nominalism]]|[[Empiricism]]<ref>{{Cite book |title=Demonstration and scientific knowledge in William of Ockham: a translation of Summa logicae III-II: De syllogismo demonstrativo, and selections from the prologue to the ordinatio |quote=Ockham may reasonably be regarded as the founder of empiricism in the European tradition. |first1=John |last1=Longeway |publisher=University of Notre Dame |year=2007 |page=3}}</ref>}}
}}

'''William of Ockham''' or '''Occam''' ({{IPAc-en|ˈ|ɒ|k|əm}} {{respell|OK|əm}}; {{langx|la|Guillelmus de Ockham}};<ref>In manuscripts of Ockham's work his name is spelled in various ways, e.g. "Okan". On the title pages of the modern critical edition his name is taken to be Guillelmus de Ockham (in the genitive case, "Guillelmi de Ockham"). The stained-glass picture reproduced above is based on a drawing in a 1341 manuscript (reproduced below),  OP, vol. 1, p.32*; it was made by a copyist who may never have seen Ockham. </ref> {{circa|1287}}{{snd}}9/10 April 1347) was an English [[Franciscan friar]], [[Scholasticism|scholastic]] [[philosopher]] and [[Theology|theologian]]. He is considered to be one of the major figures of [[medieval thought]] and was at the centre of the major intellectual and political controversies of the 14th century.<ref>William J. Courtenay, "The Academic and Intellectual Worlds of Ockham", in P.V. Spade (ed.), ''The Cambridge Companion to Ockham'' (Cambridge: Cambridge University Press, 1999), pp.17-30.</ref> The [[Nominalism|nominalists]] of the fifteenth century regarded him as one of the founders of their movement.<ref>{{Cite book |last=Thorndike |first=Lynn |title=University Records and Life in the Middle Ages |publisher=Columbia University Press |year=1949 |location=New York |pages=355-360}}</ref> He is widely known for [[Occam's razor]], the methodological principle that bears his name. He produced significant works on [[logic]], [[physics]] and theology. Ockham is [[Calendar of saints (Church of England)|remembered]] in the [[Church of England]] with a [[Commemoration (Anglicanism)|commemoration]] corresponding to the commonly ascribed date of his death on 10 April.<ref>{{Cite web |title=The Calendar |url=https://www.churchofengland.org/prayer-and-worship/worship-texts-and-resources/common-worship/churchs-year/calendar |access-date=2021-03-27 |website=The Church of England}}</ref>

==Life==
William of Ockham was probably born in [[Ockham, Surrey]], around 1287.<ref name=":1">{{Cite web |last=Courtenay |first=William J. |date=23 September 2004 |title=Ockham, William (c.1287–1347), philosopher, theologian, and political theorist |url=https://doi.org/10.1093/ref:odnb/20493 |url-status=live |access-date=31 May 2026 |website=Oxford Dictionary of National Biography}}</ref> At an early age he became a member of the Franciscan Order (Order of Friars Minor) and received the first stages of his theological education in the Franciscan school in London. From some undetermined date until probably 1321 he studied in the Franciscan school in the [[University of Oxford]].<ref name=Merton>He has long been claimed as a [[Merton College, Oxford|Merton]] alumnus, but there is no contemporary evidence to support this claim and as a Franciscan, he would have been ineligible for fellowships at Merton (see G. H. Martin and J. R. L. Highfield, ''A History of Merton College'', Oxford: Oxford University Press, 1997, p. 53). The claim that he was a pupil of [[Duns Scotus]] at Oxford is also disputed (see Philip Hughes, ''History of the Church: Volume 3: The Revolt Against The Church: Aquinas To Luther'', Sheed and Ward, 1979, p. 119 n. 2).</ref><ref>During that time (1312–1317) [[Henry Harclay]] was the [[Chancellor (education)|Chancellor]] of Oxford and it is believed that Ockham was his pupil (see John Marenbon (ed.), ''Medieval Philosophy'', Routledge, 2003, p. 329).</ref> Although he completed all the requirements for a master's degree in theology, he never was a [[regent master]]. Because of this he was later called the {{lang|la|Venerabilis Inceptor}}. (An {{lang|la|inceptor}} was someone recognized by the university as qualified to begin ("incept") as a regent master.)<ref name="Brundage">{{cite book |last=Brundage |first=James |author-link=James A. Brundage |chapter=Canon Law in the Law schools |title=The history of medieval canon law in the classical period |publisher=Catholic University of America Press |editor1-first=Wilfried |editor1-last=Hartmann |editor2-first=Kenneth |editor2-last=Pennington |year=2008 |page=115 |isbn=978-0-8132-1491-7}}</ref>

A scholar seeking to become a Master of Theology was required to give lectures on [[Peter Lombard]]'s ''[[Sentences]]''.<ref>On studies in theology in Oxford see William J. Courtenay, "Theology and Theologians from Ockham to Wyclif", in ''The History of the University of Oxford: Volume II'', J.I. Catto (ed.) and T.A.R. Evans (ed.) (Oxford: Oxford University Press, 1992), pp. 1-34.</ref> These lectures (which were usually in the form of [https://plato.stanford.edu/entries/medieval-literary/#DispQuaeQuodQues disputed questions]) were often copied and circulated, and a "Commentary on the Sentences" was often a theologian's main publication.<ref name="Roger Olson p. 350">Olson, Roger E. (1999). ''The Story of Christian Theology'', p. 350. {{ISBN|0-8308-1505-8}}</ref> Ockham's disputations on the Sentences were held probably in the years 1317-1319.<ref name=":1" /> His Sentences commentary has been edited in his ''Opera Theologica''. 

After qualifying for the Mastership, Ockham was sent by his Order to one of its schools, probably the school in London where he had previously been a student. Most of the works he produced during this time were philosophical, rather than theological. They included commentaries on several logical treatises of Aristotle, a commentary on Aristotle's ''Physics'', and a ''Summary of Logic''. His output during this time was prodigious.<ref name=":1" /> The works Ockham produced during this period have been edited in his ''Opera Philosophica''.

His teaching work was interrupted in 1324 by a summons to the papal court, at that time located in [[Avignon]], to defend his Sentences commentary.<ref name="Roger Olson p. 350" /> (An alternative hypothesis, recently proposed by George Knysh, is that he was initially appointed in Avignon as a professor of philosophy in the Franciscan school there, and that his disciplinary difficulties did not begin until 1327.)<ref>{{cite journal |last=Knysh |first=George |title=Biographical rectifications concerning William's Avignon period |journal=Franciscan Studies |volume=46 |year=1986 |pages=61–91 |jstor=41975065 |doi=10.1353/frc.1986.0020 |s2cid=162369468}}</ref> The Pope, [[Pope John XXII]], directed former [[List of chancellors of the University of Oxford|Oxford chancellor]] [[John Lutterell]], who had come to Avignon looking for advancement, to prepare a collection of suspect passages from Ockham's Sentences commentary, and a committee of theologians was appointed to review them.<ref name=":1" /> The committee's preliminary reports were critical, but the process was never brought to a conclusion.<ref name="Larsen2011">{{cite book |last=Larsen |first=Andrew E. |title=The School of Heretics: Academic Condemnation at the University of Oxford, 1277–1409 |chapter=The Investigation into William of Ockham |date=2011 |publisher=Brill |page= |doi=10.1163/9789004206625_006 |isbn=978-90-04-20662-5|pages=76-92}}</ref>

While he was in Avignon, Ockham became involved in the dispute about [[Apostolic poverty]]. The [[Rule of Saint Francis]] commanded members of the Order to practice the poverty of [[Jesus]] and his [[Apostles in the New Testament|apostles]], who, the Franciscans maintained, owned nothing either individually or "in common" (i.e. as a group). In several [[Papal bull|papal bulls]] or "constitutions" Pope John rejected the Franciscan doctrine and practice.<ref>{{Cite web |title=Translations of papal documents relating to the Franciscan idea of poverty |url=https://auctoresbritannici.org/digital-editions/ |url-status=live |access-date=1 June 2026 |website=William of Ockham Dialogus}}</ref> In ''Ad conditorem canonem'' John argued that no-one could justly consume (i.e. destroy by use) something owned by someone else (for example, food, clothing), so that provision of consumables was a transfer of ownership. He also argued that it was not possible to transfer durables to another person's use permanently without thereby transferring ownership. In ''Cum inter nonnullos'' John condemned as heresy the statement that Christ and the Apostles did not have anything individually or as a group. The Minister General (head) of the Franciscan order, [[Michael of Cesena]], asked Ockham to study the pope's bulls. Ockham found in them "a great many things that were heretical, erroneous... adverse to orthodox faith".<ref>{{Cite book |last=Ockham |first=William of |title=A Letter to the Friars Minor and Other Writings |publisher=Cambridge University Press |year=1995 |isbn=9780521358040 |location=Cambridge |pages=3}}</ref> Together with Michael, [[Bonagratia of Bergamo]], [[Francis of Marchia]] and perhaps other members of the Order, Ockham secretly left Avignon on 26 May 1328. The dissident Franciscans eventually took refuge in Munich, under the protection of the [[Holy Roman Emperor]] [[Louis IV of Bavaria]], who was also engaged in a dispute with Pope John over the question whether he ought to have obtained the Pope's approval to become Emperor.<ref name="Roger Olson p. 350" /><ref name=":1" /> On June 6, 1328, Ockham and the other dissidents were excommunicated for leaving Avignon without permission.<ref name="stanford">{{cite encyclopedia |title=William of Ockham |url=http://plato.stanford.edu/entries/ockham/ |publisher=Stanford University |encyclopedia=Stanford Encyclopedia of Philosophy |author=Spade, Paul Vincent |access-date=22 October 2006}}</ref> 

Most members of the Franciscan Order submitted to the decrees of Pope John. Ockham and other members of the small band of dissident Franciscans in Munich (the "Michaelists") campaigned for years to get John XXII and his successors Benedict XII and Clement VI deposed from the papacy.<ref>{{Cite book |last=Ockham |first=William of |title=On Heretics Books 1-5 and Against John Chapters 5-16 |publisher=Oxford University Press for the British Academy |isbn=9780197267592 |location=Oxford |publication-date=2023 |pages=1, 31-33}}</ref> The writings Ockham published during those years are often called his "political writings" (''Opera Politica''), because they deal with many matters relevant to political philosophy. After he left Avignon Ockham seems to have written nothing more on the topics of his academic work in England.<ref name=":1" /> William of Ockham died probably on either 9 or 10 April 1347 (just before the outbreak in Munich of the [[Black Death]]).<ref name="Gedeon1982">{{cite journal |last=Gál |first=Gedeon |year=1982 |title=William of Ockham Died 'Impenitent' in April 1347 |journal=Franciscan Studies |volume=42 |pages=90–95 |jstor=41974990 |doi=10.1353/frc.1982.0011 |s2cid=201793525 |quote=According to Fr. Herman ... died on April 9, 1347. A chronicler's note suggests that he died on April 10 ... Ockham's epitaph agrees with the chronicler .... How the question of whether Ockham died on the 9th or 10th is resolved is of no importance ... [and] may be due to a simple oversight.}}</ref>

==Philosophical thought==
{{Catholic philosophy}}

Ockham incorporated much of the work of some previous theologians, especially [[Duns Scotus]]. From Scotus Ockham derived his view of divine omnipotence, his view of grace and justification, much of his epistemology and ethics.<ref>Lucan Freeport, ''Basis of Morality According to William Ockham'', {{ISBN|978-0-8199-0918-3}}, Franciscan Herald Press, 1988.</ref> He disagreed with Scotus about predestination, penance, universals, and the formal distinction {{lang|la|ex parte rei}} ("on the part of the thing") in creatures. 

===Faith and reason===
William of Ockham held that theology is not a science.<ref>{{Cite book |last=Maurer |first=Armand |title=The Philosophy of William of Ockham in the Light of its Principles |publisher=Pontifical Institute of Mediaeval Studies |isbn=0-88844-133-9 |location=Toronto |publication-date=1999|pages=150-1}}</ref>  "Only faith gives us access to theological truths. The ways of God are not open to reason, for God has freely chosen to create a world and establish a way of salvation within it apart from any necessary laws that human logic or rationality can uncover."<ref>Dale T. Irvin and Scott W. Sunquist. ''History of World Christian Movement'' Volume I: Earliest Christianity to 1453, p. 434. {{ISBN|978-1-57075-396-1}}</ref> Science includes empirical knowledge and conclusions demonstrated from self-evident premises.<ref>Maurer, ''The Philosophy of William of Ockham'', pp.135-6.</ref><ref name="stanford"/> 

===Nominalism===
As noted above, fifteenth-century [[nominalism|nominalists]] regarded Ockham as one of the founders of their movement. Some modern scholars think that it would be better to call his position "terminism" or "[[conceptualism]]" rather than "nominalism", because in Ockham's view individuals are not only names (understood as spoken words) but also concepts, which occur as "terms" in a statement (spoken, written or thought). Universals (e.g. "human being") are individuals -- sounds in the air, inscriptions on paper or other surfaces, or concepts (mental pictures or mental acts) -- that signify or stand for other individuals (e.g. Socrates, Plato, Joe Blow). A universal can stand for many things because those things are similar to one another. Ockham did not hold that resemblances are imposed by the human mind: really, i.e. truly, apart from human thinking, some things resemble some other things.<ref>Maurer, ''The Philosophy of William of Ockham'', pp. 62-4, 84-7, 48.</ref>

===Efficient reasoning===
One important contribution that he made to modern science and modern intellectual culture was efficient reasoning with 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]],<ref name="russell">{{cite book |last=Russell |first=Bertrand |title=[[A History of Western Philosophy]] |publisher=[[Allen & Unwin]] |year=2000 |isbn=0-415-22854-9 |pages=462–463 |author-link=Bertrand Russell}}</ref> 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 causes, factors, or variables. He turned this into a concern for ontological parsimony; the principle says that one should not multiply entities beyond necessity—{{lang|la|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.<ref name="thorburn">{{cite journal |url=https://en.wikisource.org/wiki/The_Myth_of_Occam's_Razor |title=The Myth of Occam's Razor |journal=[[Mind (journal)|Mind]] |first=W. M. |last=Thorburn |volume=27 |issue=107 |pages=345–353 |year=1918 |doi=10.1093/mind/XXVII.3.345 |access-date=15 May 2022|url-access=subscription }}</ref> 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."<ref>Spade, Paul Vincent (ed.). ''The Cambridge Companion to Ockham''. Cambridge University Press, 1999, p. 104.</ref> For William of Ockham, the only truly necessary entity is God; everything else is contingent. He thus does not accept the [[principle of sufficient reason]], rejects the distinction between essence and existence, and opposes the [[Thomism|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.<ref name="Turner1913">{{Catholic Encyclopedia| year=1913|wstitle = William of Ockham | author =William Turner|inline=yes}}</ref>

===Natural philosophy===
Ockham wrote a great deal on [[natural philosophy]], including a long commentary on Aristotle's [[Physics (Aristotle)|''Physics'']].<ref>André Goddu, ''The Physics of William of Ockham'',  {{ISBN|978-90-04-06912-1}}, Brill Academic Pub., 1984.</ref> 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''.

===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. Interpreters are, as yet, undecided about the roles of these two types of cognitive activities.<ref>{{cite journal |last1=Brower-Toland |first1=S |title=William ockham on the scope and limits of consciousness |journal=Vivarium |date=2014 |volume=52 |issue=3–4 |pages=197–219 |doi=10.1163/15685349-12341275 |url=https://philpapers.org/rec/BROQOO}}</ref>

===Political theory===
William of Ockham is also increasingly being recognized as an important contributor to the development of Western constitutional ideas, especially those of government with limited responsibility.<ref name="SEP">[https://plato.stanford.edu/entries/ockham/#8 "William of Ockham"]. ''Stanford Encyclopedia of Philosophy''.</ref> He was one of the first medieval authors to advocate a form of church/state separation,<ref name="SEP"/> 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.<ref name="SEP"/> The views on monarchical accountability espoused in his ''Dialogus'' (written between 1332 and 1347)<ref>{{cite web |url=https://auctoresbritannici.org/digital-editions/ |publisher=British Academy |title=William of Ockham: Dialogus|access-date=30 May 2026|website=Auctores Britannici Medii Aevi|url-status=live}}</ref> greatly influenced the [[Conciliarism|Conciliar movement]].<ref>{{cite book |last1=Tierney |first1=Brian |title=Foundations of the conciliar theory: the contribution of the medieval canonists from Gratian to the Great Schism |date=1998 |publisher=Brill |location=Leiden |isbn=978-90-04-10924-7 |edition=Enlarged |author-link=Brian Tierney (medievalist)}}</ref> This tract on heresy had the ultimate purpose to establish the possibility of papal heresy and to consider what action should be taken against a pope who had become a heretic.<ref>{{cite web |url=https://publications.thebritishacademy.ac.uk/pubs/dialogus/frmIntro1d1.html|first=John |last=Scott|title=Theologians vs Canonists on Heresy|archive-url=https://archive.today/20250324113310/https://publications.thebritishacademy.ac.uk/pubs/dialogus/frmIntro1d1.html|website=[[British Academy]] |archive-date=March 24, 2025 |url-status=live}}</ref>

Ockham argued for complete separation of spiritual rule and earthly rule.<ref>Takashi Shogimen, ''Ockham and Political Discourse in the Late Middle Ages''. {{ISBN|978-0-521-84581-6}}, Cambridge University Press, 2007.</ref> He thought that the pope and churchmen have no right or grounds at all for secular rule like having property, citing 2 Timothy 2:4. That belongs solely to earthly rulers, who may also accuse the pope of crimes, if need be.<ref name=vm>Virpi Mäkinen, ''Keskiajan aatehistoria'', Atena Kustannus Oy, Jyväskylä, 2003, {{ISBN|978-951-796-310-7}}. pp. 160, 167–168, 202, 204, 207–209.</ref>

After the [[Fall of man|Fall]] he believed God had given humanity, including non-Christians, two powers: private ownership and the right to set their rulers, who should serve the interest of the people, not some special interests. Thus he preceded [[Thomas Hobbes]] in formulating [[social contract]] theory along with earlier scholars.<ref name=vm/>

William of Ockham said that the Franciscans avoided both private and common ownership by using commodities, including food and clothes, without any rights, with mere {{lang|la|usus facti}}, the ownership still belonging to the donor of the item or to the pope. Their opponents such as [[Pope John XXII]] wrote that use without any ownership cannot be justified: "It is impossible that an external deed could be just if the person has no right to do it."<ref name=vm/>

Thus the disputes on the heresy of Franciscans led Ockham and others to formulate some fundamentals of economic theory and the theory of ownership.<ref name=vm/>

According to John Kilcullen, "Ockham's Utilitarian theory of property, his defence of civil and (within limits) religious liberty, and his emphasis on the inevitability of exceptions to rules and the need to adapt institutions to changing circumstances, anticipate [[John Stuart Mill|J.S. Mill]]" (via Aristotle).<ref>{{cite web|first=John|last=Kilcullen|title=Ockham's Political Writings|publisher=Cambridge University Press|year=1999|url=https://publications.thebritishacademy.ac.uk/pubs/dialogus/polth.html|access-date=March 24, 2025|archive-date=24 March 2025|archive-url=https://archive.today/20250324115229/https://publications.thebritishacademy.ac.uk/pubs/dialogus/polth.html|url-status=bot: unknown}}</ref>

===Logic===
In [[logic]], William of Ockham wrote down in words the formulae that would later be called [[De Morgan's laws]],<ref>In his ''Summa Logicae'', part II, sections 32 and 33.Translated on p. 80 of ''Philosophical Writings'', tr. [[Philotheus Boehner|P. Boehner]], rev. S. Brown, (Indianapolis, Indiana, 1990)</ref> and he pondered [[three-valued logic|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. His contributions to [[semantics]], especially to the maturing [[theory of supposition]], are still studied by logicians.<ref>{{cite journal |first1=Graham |last1=Priest |author-link1=Graham Priest |last2=Read |first2=S. |title=The Formalization of Ockham's Theory of Supposition |journal=Mind |volume=LXXXVI |pages=109–113 |year=1977 |doi=10.1093/mind/LXXXVI.341.109 |issue=341}}</ref><ref>{{cite journal |author-link1=John Corcoran (logician) |first1=John |last1=Corcoran |first2=John |last2=Swiniarski |year=1978 |title=Logical Structures of Ockham's Theory of Supposition |journal=Franciscan Studies |volume=38 |pages=161–183 |jstor=41975391 |doi=10.1353/frc.1978.0010 |s2cid=170450442}}</ref> William of Ockham was probably the first logician to treat empty terms in Aristotelian syllogistic effectively; he devised an empty term semantics that exactly fit the syllogistic. Specifically, an argument is valid according to Ockham's semantics if and only if it is valid according to ''Prior Analytics''.<ref>John Corcoran (1981). "Ockham's Syllogistic Semantics", ''Journal of Symbolic Logic'', '''46''': 197–198.</ref>

=== Philosophy of Time ===
William of Ockham believed that [[eternity]] was exclusive to God.<ref name="Steel2001">{{Cite journal |last=Steel |first=Carlos |date=2001-06-21 |editor-last=Porro |editor-first=Pasquale |title=The Neoplatonic Doctrine of Time and Eternity and its Influence on Medieval Philosophy |url=https://brill.com/display/book/edcoll/9789004453197/B9789004453197_s003.xml |journal=The Medieval Concept of Time |pages=3–31 |doi=10.1163/9789004453197_003 |isbn=978-90-04-45319-7|url-access=subscription }}</ref> He rejected the concept of the [[aevum]] as a special measure of duration of for angels.<ref name="Steel2001" /> He also said it is not proper to call eternity a measure of duration.<ref name="Steel2001" /> In Ockham's view, there was only one measure of duration, time, which was shared by all creation.<ref name="Steel2001" />

== Theological thought ==

=== Church authority ===
William of Ockham denied [[papal infallibility]] and often went into conflict with the pope.<ref>{{Cite web |title=William of Ockham: Defending the Church, Condemning the Pope |url=https://philosophynow.org/issues/56/William_of_Ockham_Defending_the_Church_Condemning_the_Pope |access-date=2022-09-08 |website=PhilosophyNow.org}}</ref> As a result, some theologians have viewed him as a [[Proto-Protestantism|proto-Protestant]].<ref name="Ford 2016 p. 84">{{cite book |last=Ford |first=J.L. |title=The Divine Quest, East and West: A Comparative Study of Ultimate Realities |publisher=State University of New York Press |year=2016 |isbn=978-1-4384-6055-0 |url=https://books.google.com/books?id=Tk14CwAAQBAJ&pg=PA84 |access-date=2023-06-16 |page=84}}</ref> However, despite his conflicts with the papacy he did not renounce the [[Catholic Church|Roman Catholic Church]].<ref name="iep.utm.edu">{{Cite web |title=Ockham (Occam), William of {{!}} Internet Encyclopedia of Philosophy |url=https://iep.utm.edu/ockham/ |access-date=2022-09-08}}</ref> Ockham also held that councils of the Church were fallible, he held that any individual could err on matters of faith, and councils being composed of multiple fallible individuals could err.<ref>{{Cite book |last=Canning |first=Joseph |url=https://books.google.com/books?id=fpMdtNgggN8C&dq=William+of+Ockham+papal+power&pg=PA131 |title=Ideas of Power in the Late Middle Ages, 1296–1417 |year=2011 |publisher=Cambridge University Press |isbn=978-1-139-50495-9 |language=en}}</ref> He thus foreshadowed some elements of Luther's view of [[sola scriptura]].<ref name=":0">{{Cite book |last=Thiel |first=John E. |url=https://books.google.com/books?id=IZ5CelJGUYEC&dq=William+of+Ockham+sola+scriptura&pg=PA18 |title=Senses of Tradition: Continuity and Development in Catholic Faith |date=2000 |publisher=Oxford University Press |isbn=978-0-19-535031-9}}</ref><ref name=":2">{{Cite book |last=Heath |first=J. M. F. |url=https://books.google.com/books?id=LfunhfdzJskC&dq=William+of+Ockham+sola+scriptura&pg=PA22 |title=Paul's Visual Piety: The Metamorphosis of the Beholder |date=2013 |publisher=OUP Oxford |isbn=978-0-19-966414-6 |language=en}}</ref><ref name=":3">{{Cite book |last1=McGregor |first1=Peter John |url=https://books.google.com/books?id=zOFaEAAAQBAJ&dq=William+of+Ockham+protestant&pg=PT101 |title=Healing Fractures in Contemporary Theology |last2=Rowland |first2=Tracey |date=2022 |publisher=Wipf and Stock Publishers |isbn=978-1-7252-6610-0}}</ref>

=== Church and State ===
Ockham taught the [[separation of church and state]], believing that the pope and emperor should be separate.<ref name="iep.utm.edu"/>

Ockham adversed papal ''[[plenitudo potestatis]]'':<ref name="Marsilius of Padua" /> even the famous [[allegory]] of the [[Sun and Moon allegory|Sun-Pope/Moon-Emperor]] is contradicted by Our Lord, who, while admitting the greater/lower opposition (Ockham holds spiritual power and the Church's own functions in the highest esteem; in this sense, and only in this sense, does he consider them of greater importance), does not concede to the Curialists, defenders of the fullness of papal power, the argument that the Moon originated from the Sun.<ref name="Marsilius of Padua" />

According to Ockham, the Pope obtains his power from the Council and, therefore, from the whole of all believers. In the same way, the elected Emperor is depositary of a power whose origin lies in the people who are always the authentic sovereign. 
Ockham developed in canon law the theories that [[Marsilius of Padua]] had promoted in civil law<ref name="Marsilius of Padua">{{cite web|title=Marsilius of Padua and William of Ockham in Papal Plenitudo Potestatis|access-date=March 24, 2025|url=https://mta.cairnrepo.org/islandora/object/mta%3A29120/datastream/PDF/download/mta_29120.pdf|archive-date=24 March 2025|archive-url=https://web.archive.org/web/20250324100412/https://mta.cairnrepo.org/islandora/object/mta%3A29120/datastream/PDF/download/mta_29120.pdf|url-status=bot: unknown}}</ref> (e.g. [[popular sovereignty]]).<ref>{{cite journal |format=PDF |via=Academia |url=https://www.academia.edu/3730416 |title=Natural liberty and transference of sovereignty in William |author =Manuel Mendez Alonzo |date=2013 |journal=Revista Española de Filosofía Medieval |number=20 |page=66 |access-date=March 24, 2025}}</ref>

=== Apostolic poverty ===
Ockham advocated for voluntary poverty.<ref>{{Cite magazine |title=The Right to Be Poor |issue=118 |url=https://philosophynow.org/issues/118/The_Right_to_Be_Poor |access-date=2022-09-08 |magazine=Philosophy Now}}</ref>

=== Soul ===
Ockham opposed Pope John XXII on the question of the Beatific Vision. John had proposed that the souls of Christians did not instantly get to enjoy the vision of God, rather such vision would be postponed until the last judgement.<ref>{{Cite encyclopedia |title=William of Ockham |url=https://www.britannica.com/biography/William-of-Ockham |access-date=2022-09-09 |encyclopedia=Britannica |language=en}}</ref>

=== Voluntarism ===
William of Ockham was a theological [[Voluntarism (theology)|voluntarist]] who believed that if God had wanted to, he could have become incarnate as a donkey or an ox, or even as both a donkey and a man at the same time. He was criticized for this belief by his fellow theologians and philosophers.<ref name="grenz">{{cite book |author=[[Stanley Grenz|Stanley J. Grenz]] |title=The Named God and the Question of Being: A Trinitarian Theo-Ontology}}</ref>

==Literary Ockhamism/nominalism==
William of Ockham and his works have been discussed as a possible influence on several late medieval literary figures and works, especially [[Geoffrey Chaucer]], but also [[Jean Molinet]], the [[Sir Gawain and the Green Knight|''Gawain'']] poet, [[François Rabelais]], [[John Skelton (poet)|John Skelton]], [[Julian of Norwich]], the York and [[Townely Plays]], and Renaissance romances. Only in very few of these cases is it possible to demonstrate direct links to William of Ockham or his texts. Correspondences between Ockhamist and Nominalist philosophy/theology and literary texts from medieval to postmodern times have been discussed within the scholarly paradigm of [[literary nominalism]].<ref>
*William H. Watts and [[Richard Utz|Richard J. Utz]], "Nominalist Influence on Chaucer's Poetry: A Bibliographical Essay", ''Medievalia & Humanistica'' 20 n.s. (1993), 147–173.
*Helen Ruth Andretta, ''Chaucer's 'Troilus and Criseyde'. A Poet's Response to Ockhamism'' (New York: Lang, 1997).
*Richard Utz, ed., ''Literary Nominalism and the Theory of Rereading Late Medieval Texts: A New Research Paradigm''. Lewiston, New York: Mellen, 1995.
*''Nominalism and Literary Discourse: New Perspectives''. Ed. Hugo Keiper, R. Utz, and Christoph Bode. Amsterdam: Rodopi, 1997.</ref> Erasmus, in his ''Praise of Folly'', criticized him together with Duns Scotus as fuelling unnecessary controversies inside the Church.

==Works==
[[File:William of Ockham - Logica 1341.jpg|thumb|upright=1.25|Sketch labelled {{lang|la|"frater Occham iste"}}, from a manuscript of Ockham's {{lang|la|Summa Logicae}}, 1341]]
[[File:Guillelmus - Quaestiones in quattuor libros sententiarum - 4417303 Carta 25r.tif|thumb|upright=0.8|{{lang|la|Quaestiones in quattuor libros sententiarum}}]]
The standard edition of the philosophical and theological works is: ''William of Ockham: {{lang|la|Opera philosophica et theologica}}'', Gedeon Gál, et al., eds. 17&nbsp;vols. [[St. Bonaventure University|St. Bonaventure]], New York: The Franciscan Institute, 1967–1988. Republished in electronic form by [[InteLex Past Masters|Intelex]].  Abbreviations: OT = {{lang|la|Opera Theologica}} vol. 1–10; OP = {{lang|la|Opera Philosophica}} vol. 1–7.

OP 7 contains the doubtful and spurious works.

The political works, all but the {{lang|la|Dialogus}}, have been edited in [[H. S. Offler]], et al., eds. {{lang|la|Guilelmi de Ockham Opera Politica}}, 4 vols., 1940–1997, Manchester: Manchester University Press [vols. 1–3]; Oxford: Oxford University Press [vol. 4]. 

The ''Dialogus'' has now been edited and published in print in the British Academy series Auctores Britannici Medii Aevi. The [https://auctoresbritannici.org/digital-editions/ Dialogus website] includes translation of the whole work.

===Philosophical writings===
* {{lang|la|Summa logicae}} (''[[Sum of Logic]]'') (c. 1323, OP 1).
* {{lang|la|Expositionis in Libros artis logicae prooemium}}, 1321–1324, OP 2).
* {{lang|la|Expositio in librum Porphyrii de Praedicabilibus}}, 1321–1324, OP 2).
* {{lang|la|Expositio in librum Praedicamentorum Aristotelis}}, 1321–1324, OP 2).
* {{lang|la|Expositio in librum in librum Perihermenias Aristotelis}}, 1321–1324, OP 2).
* {{lang|la|Tractatus de praedestinatione et de prescientia dei respectu futurorum contingentium}} (''Treatise on Predestination and God's Foreknowledge with respect to Future Contingents'', 1322–1324, OP 2).
* {{lang|la|Expositio super libros Elenchorum}} (''Exposition of Aristotle's Sophistic refutations'', 1322–1324, OP 3).
* {{lang|la|Expositio in libros Physicorum Aristotelis. Prologus et Libri I–III}} (''Exposition of Aristotle's Physics'') (1322–1324, OP 4).
* {{lang|la|Expositio in libros Physicorum Aristotelis. Prologus et Libri IV–VIII}} (''Exposition of Aristotle's Physics'') (1322–1324, OP 5).
* {{lang|la|Brevis summa libri Physicorum}} (''Brief Summa of the Physics'', 1322–23, OP 6).
* {{lang|la|Summula philosophiae naturalis}} (''Little Summa of Natural Philosophy'', 1319–1321, OP 6).
* {{lang|la|Quaestiones in libros Physicorum Aristotelis}} (''Questions on Aristotle's Books of the Physics'', before 1324, OP 6).

===Theological writings===
* {{lang|la|In libros Sententiarum}} (''Commentary on the Sentences of Peter Lombard'').
** Book I ({{lang|la|Ordinatio}}) completed shortly after July 1318 (OT 1–4).
** Books II–IV ({{lang|la|Reportatio}}) 1317–18 (transcription of the lectures; OT 5–7).
* {{lang|la|Quaestiones variae}} (OT 8).
* {{lang|la|Quodlibeta septem}} (before 1327) (OT 9).
* {{lang|la|Tractatus de quantitate}} (1323–24. OT 10).
* {{lang|la|Tractatus de corpore Christi}} (1323–24, OT 10).

===Political writings===
* {{lang|la|Opus nonaginta dierum}} (1332–1334).
* {{lang|la|Epistola ad fratres minores}} (1334).
* {{lang|la|Dialogus}} (before 1335).
* {{lang|la|Tractatus contra Johannem}} [XXII] (1335).
* {{lang|la|Tractatus contra Benedictum}} [XII] (1337–38).
* {{lang|la|Octo quaestiones de potestate papae}} (1340–41).
* {{lang|la|Consultatio de causa matrimoniali}} (1341–42).
* {{lang|la|Breviloquium}} (1341–42).
* {{lang|la|De imperatorum et pontificum potestate}} [also known as {{lang|la|Defensorium}}] (1346–47).

===Doubtful writings===
* {{lang|la|Tractatus minor logicae}} (''Lesser Treatise on logic'') (1340–1347?, OP 7).
* {{lang|la|Elementarium logicae}} (''Primer of logic'') (1340–1347?, OP 7).

===Spurious writings===
* {{lang|la|Tractatus de praedicamentis}} (OP 7).
* {{lang|la|Quaestio de relatione}} (OP 7).
* {{lang|la|Centiloquium}} (OP 7).
* {{lang|la|Tractatus de principiis theologiae}} (OP 7).

===Translations===
====Philosophical works====
*''Philosophical Writings'', tr. [[Philotheus Boehner|P. Boehner]], rev. S. Brown (Indianapolis, Indiana, 1990)
*''Ockham's Theory of Terms: Part I of the {{lang|la|Summa logicae}}'', translated by [[Michael J. Loux]] (Notre Dame; London: University of Notre Dame Press, 1974) [translation of {{lang|la|Summa logicae}}, part 1]
*''Ockham's Theory of Propositions: Part II of the {{lang|la|Summa logicae}}'', translated by [[Alfred J. Freddoso]] and Henry Schuurman (Notre Dame: University of Notre Dame Press, 1980) [translation of {{lang|la|Summa logicae}}, part 2]
*''Demonstration and Scientific Knowledge in William of Ockham: a Translation of {{lang|la|Summa logicae}} III-II, {{lang|la|De syllogismo demonstrativo}}, and Selections from the Prologue to the {{lang|la|Ordinatio}}'', translated by John Lee Longeway (Notre Dame, Indiana: University of Notre Dame, 2007)
*''Falacies: Part 3, Book 4 of {{lang|la|Summa logicae}}'', translated by Richard Robinson (Sunny Lou Publishing, 2025.)<ref>{{Cite web|title=Fallacies: Part 3, Book 4 of Summa Logicae|url=http://www.sunnyloupublishing.com|access-date=2025-06-14|website=Sunny Lou Publishing|language=en-US}}</ref>
*''Ockham on Aristotle's Physics: A Translation of Ockham's {{lang|la|Brevis Summa Libri Physicorum}}'', translated by Julian Davies (St. Bonaventure, New York: The Franciscan Institute, 1989)
*Kluge, Eike-Henner W., "William of Ockham's Commentary on Porphyry: Introduction and English Translation", ''Franciscan Studies'' '''33''', pp.&nbsp;171–254, {{JSTOR|41974891}}, and '''34''', pp.&nbsp;306–382, {{JSTOR|44080318}} (1973–74)
*''Predestination, God's Foreknowledge, and Future Contingents'', translated by Marilyn McCord Adams and Norman Kretzmann (New York: Appleton-Century-Crofts, 1969) [translation of {{lang|la|Tractatus de praedestinatione et de praescientia Dei et de futuris contigentibus}}]
*''Quodlibetal Questions'', translated by Alfred J. Freddoso and Francis E. Kelley, 2 vols (New Haven; London: Yale University Press, 1991) (translation of {{lang|la|Quodlibeta septem}})
* Paul Spade, ''Five Texts on the Mediaeval Problem of Universals: Porphyry, Boethius, Abelard, Duns Scotus, Ockham'' (Indianapolis, Indiana: Hackett, 1994) [Five questions on Universals from His {{lang|la|Ordinatio}} d. 2 qq. 4–8]
* {{lang|la|Tractatus de principiis theologiae}}, translated in ''A compendium of Ockham's teachings: a translation of the {{lang|la|Tractatus de principiis theologiae}}'', translated by Julian Davies (St. Bonaventure, New York: Franciscan Institute, St. Bonaventure University, 1998)

====Theological works====
*''The {{lang|la|De sacramento altaris}} of William of Ockham'', translated by T. Bruce Birch (Burlington, Iowa: Lutheran Literary Board, 1930) [translation of ''Treatise on Quantity'' and ''On the Body of Christ'']

====Political works====
*{{lang|la|An princeps pro suo succursu, scilicet guerrae, possit recipere bona ecclesiarum, etiam invito papa}}, translated Cary J. Nederman, in ''Political thought in early fourteenth-century England: treatises by Walter of Milemete, William of Pagula, and William of Ockham'' (Tempe, Arizona: Arizona Center for Medieval and Renaissance Studies, 2002)
*''A translation of William of Ockham's Work of Ninety Days'', translated by John Kilcullen and John Scott (Lewiston, New York: E. Mellen Press, 2001) [translation of {{lang|la|Opus nonaginta dierum}}]
*''On the Power of Emperors and Popes'', translated by Annabel S. Brett (Bristol, 1998)
*Rega Wood, ''Ockham on the Virtues'' (West Lafayette, Indiana: Purdue University Press, 1997) [includes translation of ''On the Connection of the Virtues'']
*''A Letter to the Friars Minor, and Other Writings'', translated by John Kilcullen (Cambridge: Cambridge University Press, 1995) [includes translation of {{lang|la|Epistola ad Fratres Minores}}; some chapters of the ''Work of Ninety Days''; some chapters of the ''Dialogus''; and ''Eight Questions'', Q.3, ]
*''A Short Discourse on the Tyrannical Government'', translated by John Kilcullen (Cambridge: Cambridge University Press, 1992) [translation of {{lang|la|Breviloquium de principatu tyrannico}}]
*[https://auctoresbritannici.org/digital-editions/ Dialogus] [translation of the whole work, except for chapters translated in ''A Letter to the Friars Minor'']
* William of Ockham, [Question One of] ''Eight Questions on the Power of the Pope'', translated by Jonathan Robinson<ref>{{cite web |url=http://individual.utoronto.ca/jwrobinson/#Translations |title=Jonathan Robinson |website=individual.utoronto.ca}}</ref>

==In fiction==
William of Ockham served as an inspiration for the creation of [[William of Baskerville]], the main character of [[Umberto Eco]]'s novel ''[[The Name of the Rose]]'' (although Ockham is also mentioned as a separate character to, and a friend of, Baskerville), and is the main character of ''[[La Abadía del Crimen]]'' (''The Abbey of Crime''), a video game based upon said novel.

In the movie ''[[Star Trek VI: The Undiscovered Country]]'', [[Spock]] claims that “an ancestor” of his is responsible for Occam’s Razor.

==See also==
* [[Gabriel Biel]]
* [[Philotheus Boehner]]
* [[List of Catholic clergy scientists]]
* [[List of scholastic philosophers]]
* [[Ernest Addison Moody]]
* [[Ockham algebra]]
* [[Oxford Franciscan school]]
* [[Rule according to higher law]]
* [[Terminism]]

==Notes==
{{notelist}}

==References==
{{reflist|30em}}

==Further reading==
* {{cite book |last=Adams |first=Marilyn |author-link=Marilyn McCord Adams |title=William Ockham |publisher=University of Notre Dame Press |location=Notre Dame |year=1987 |isbn=0-268-01940-1}}
* {{cite book |last=Beckmann |first=Jan |title=Ockham-Bibliographie, 1900–1990 |publisher=F. Meiner Verlag |location=Hamburg |year=1992 |isbn=978-3-7873-1103-3}}
* {{Cite book |publisher=Franciscan Herald Press |isbn=978-0-8199-0918-3 |last=Freppert |first=Lucan |title=The Basis of Morality According to William Ockham |year=1988}}
* {{cite book |year=2010 |last=Keele |first=Rondo |title=Ockham Explained: From Razor to Rebellion |url=https://books.google.com/books?id=ErwS66U8ZW0C |location=Chicago and La Salle, Illinois |publisher=[[Open Court Publishing Company|Open Court]] |isbn=978-08126-965-09 |access-date=19 November 2012}}
* {{cite book |last=Knysh |first=George |title=Political Ockhamism |publisher=WCU Council of Learned Societies |location=Winnipeg |year=1996 |isbn=978-1-896637-00-6}}
* {{Cite book |last=Labellarte |first=Alberto |title=Logica, conoscenza e filosofia della natura in Guglielmo di Ockham |publisher=Gruppo Albatros Il Filo |location=Roma |year=2015 |isbn=978-88-567-7421-4}}
* {{cite journal |last=Lenzen |first=Wolfgang |year=2015 |title=Ockham's Calculus of Strict Implication |journal=[[Logica Universalis]] |volume=9 |issue=2 |pages=181–191 |doi=10.1007/s11787-014-0114-4 |s2cid=11132528}}
* {{Cite book |last=McGrade |first=Arthur Stephen |title=The Political Thought of William Ockham |publisher=Cambridge University Press |isbn=978-0-521-52224-3 |year=2002}}
* {{cite book |last=Panaccio |first=Claude |title=Ockham on Concepts |publisher=Ashgate |location=Aldershot |year=2004 |isbn=978-0-7546-3228-3}}
* {{cite book |last=Pelletier |first=Jenny |title=William Ockham on Metaphysics. The Science of Being and God |publisher=Brill |location=Leiden |year=2012 |isbn=978-9-0042-3015-6}}
* {{cite book |last=Robinson |first=Jonathan |title=William of Ockham's Early Theory of Property Rights in Context |publisher=Brill |location=Leiden |year=2012 |isbn=978-9-0042-4346-0}}
* {{cite book |last=Schierbaum |first=Sonja |title=Ockham's Assumption of Mental Speech: Thinking in a World of Particulars |publisher=Brill |location=Leiden |year=2014 |isbn=978-9-0042-7734-2}}
*{{cite book |last1=Sober |first1=Elliott |title=Ockham's razors |date=2015 |publisher=Cambridge University Press |location=Cambridge |isbn=978-1-107-06849-0 |url=https://archive.org/details/elliott-sober-ockham-s-razors-a-user-s-manual-2015 |access-date=16 October 2025}}
* {{cite book |last=Spade |first=Paul |title=The Cambridge Companion to Ockham |publisher=Cambridge University Press |location=Cambridge |year=1999 |isbn=0-521-58244-X}}
* {{Cite book |publisher=Purdue University Press |isbn=978-1-55753-097-4 |last=Wood |first=Rega |title=Ockham on the Virtues |year=1997}}

==External links==
{{Commons category|William of Ockham}}
{{wikiquote}}
{{wikisource|works=or}}
* [https://pvspade.com/Logic/ Mediaeval Logic and Philosophy], maintained by Paul Vincent Spade
* {{SEP|ockham|William of Ockham|Paul Vincent Spade, Claude Panaccio, Jenny Pelletier}}
* [https://iep.utm.edu/ockham/ William of Ockham] at the [[Internet Encyclopedia of Philosophy]]
* [https://web.archive.org/web/20030211022954/http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Ockham.html William of Ockham biography] at University of St Andrews, Scotland
* [https://auctoresbritannici.org/digital-editions/ Dialogus, text translation and studies] at British Academy, UK
* [https://johnkilcullen.net/Ockham.html Ockham], various articles by John Kilcullen
* [https://www.ontology.co/william-ockham.htm The Nominalist Ontology of William of Ockham], with an annotated bibliography
*[http://www.uni-due.de/imperia/md/content/perspicuitas/nominalism_medieval.pdf Richard Utz and Terry Barakat, "Medieval Nominalism and the Literary Questions: Selected Studies." ''Perspicuitas '']
* [[s:The Myth of Occam's Razor|The Myth of Occam's Razor]] by William M. Thorburn (1918)
* [https://www.bbc.co.uk/programmes/b007m0w4 BBC Radio 4 'In Our Time' programme on Ockham] Download and listen
* {{DNB-Portal|118633015}}
* {{DDB|Person|118633015}}
* {{Geschichtsquellen Person|118633015|Occam, Guillelmus}}

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