Occam’s (or Ockham’s) Razor is a form of the principle of parsimony (broadly, that theories should be as simple as possible but not simpler.) It states: ‘Entities should not be multiplied without necessity.’ (In Latin, Entia non sunt multiplicanda praeter necessitatem.) However it seems that William of Occam never said it. As the Stanford Encyclopaedia of Philosophy reports:
Although the sentiment is certainly Ockham’s, that particular formulation is nowhere to be found in his texts. Moreover, as usually stated, it is a sentiment that virtually all philosophers, medieval or otherwise, would accept; no one wants a needlessly bloated ontology. The question, of course, is which entities are needed and which are not.
The other question is, who did originally say it? In 1918, William Thorburn published the result of his investigations into this question in Mind. The paper is available from Mind 27 (1918), 345-353; and on wikisource. That research suggested the origin lay with an Irish scholastic, John Punch.
Thorburn discovered many places the phrase was not found: the works of Occam, Scotus, or Aquinas; in “the two most popular textbooks of the Middle Ages, the Sentences of Peter Lombard (Bishop of Paris, +1164), and the Summulae Logicales of Petrus Hispanus”; or in Abelard, Hales, Albert, Bonaventura, and Durand. He also searched histories of medieval philosophy and found nothing. The phrase associated with Occam relating to parsimony seemed to be ‘Pluralitas non est ponenda sine necessitate’ (and variants thereof): ‘Entities should not be posited without necessity’.
Thorburn finds the phrase first associated with Occam by Tenneman in his history Grundriss der Geschichte der Philosophie (1812) which states that Occam followed the rule Entia non sunt multiplicanda prseter necessitatem without ascribing the actual words to Occam.
Searching for a form of words similar to ‘Occam’s Razor’, Thorburn finds it cited as a general rule in an Inaugural Dissertation, De Stylo Philosophico Marii Nizolii by Leibnitz in 1670, and a similar version in Clauberg‘s Elementa Philosophice seut Ontosophia (Groningen, 1647). The earliest quote similar to the Razor that he finds is in a commentary contained in Wadding’s edition of Duns Scotus’s philosophy (1639). There John Ponce of Cork says that there is a common axiom used frequently by the Scholastics; entities must not be multiplied without necessity: “illud axioma vulgare, quo tam frequentei, utuntur Scholastici; non sunt multiplicanda entia sine necessitate“. No specific scholastic is mentioned.
Thorburn concludes that this is probably the root source of the phrase, that it
was invented in 1639, substantially in its present wording, by the Scotist Commentator, John Ponce of Cork: a little-known man of great abilities and very independent disposition.
John Pounce (also known as John Punch) was born in 1603 of Anglo-Irish parents. We know nothing of his life before his entrance into the novitiate of the Irish Franciscans at St Anthony’s College, Louvain. After his novitiate he studied at Cologne, then returned to Louvain to study under the Irish historians, John Colgan and Hugh Ward. Academically brilliant, he came to the attention of Luke Wadding, who requested that he be one of the first students to enter the newly established Irish Franciscan college of St Isidore in Rome on 7 September 1625.
He became professor of philosophy at St Isidore on completing his studies, succeeding his own professor Patrick Fleming, and later professor of theology. He was a champion of the teaching of John Duns Scotus, a 13th century philosopher. Like many at the time Punch believed Duns Scotus to be Irish. This contributed to the dedication of Irish philosophers to Scotus, and to St Isidore’s emergence as the leading Scotist school.
He worked with Luke Wadding in producing the first (and to date only) full edition of the works of Scotus, published in 1639 in Lyons. He also produced what he claimed was the first complete course on Scotus, Philosophiae ad mentem Scoti cursus integer (1642–3). His approach was regarded as revolutionary by his colleagues, attracting criticism. Punch replied that he accepted Scotus’ conclusions but not necessarily all the proofs Scotus outlined.
He was also involved in Irish politics, acting as an agent in Rome for the confederate Catholics in the 1640s. After 1648 Punch was primarily based in Paris. While in France he became involved in a long-running dispute in print with Richard Bellings, secretary of the confederate supreme council, over the conduct of the revolt in Ireland. He took part in the debate between John Colgan and the English friar Angelus Mason over the nationality of John Duns Scotus, rebutting Mason in 1660 after Colgan’s death. Punch’s last publication was in 1661; the date of his death is uncertain, being either 1660-2 or 1672-3.
Thorburn attributes the first use of the principle of parsimony in science to Isaac Newton in 1713, where he quoted the words of Scotus and Ockham in a note to his Regula Philosophandi. The first use in English of the name ‘Occam’s Razor’ that Thorburn found was Sir William Hamilton’s (1852) Discussions (archive.org). In the 1853 edition, Thorburn reports, the phrase (in its first appearance in English) and the name “Occam’s Razor” are definitively linked by Hamilton.
However the Razor was used earlier in English, and in a debate with Isaac Newton. In 1672 Hooke criticised Newton’s theory about colours in light, reportedly saying,
there are an indefinite variety of primary or original colours, amongst which are yellow, green, violet, purple, orange, &c. and an infinite number of intermediate gradations, I cannot assent thereunto, as supposing it wholly useless to multiply entities without necessity
In his reply Newton repeats the phrase: ” I see no reason why they, that adhere to any of those hypotheses, should seek for other Causes of these Effects, unless (to use the Objectors argument) they will multiply entities without necessity.”
So it seems that Hooke was the first to use the phrase itself in English, and in the context of natural philosophy. It would be interesting to know if this was indeed the earliest use and how it travelled (if it did) from Punch’s commentary in Wadding’s edition of John Duns Scotus. Please comment if you have any additional information.
Update: Felicity Henderson who is currently working on a edition of Robert Hooke’s diary very kindly checked the list of books Hooke owned. Wadding’s was not among them. Of course he could have studied the scholastics in Oxford, or got the aphorism from a colleague (Robert Boyle studied the scholastics while on his continental tour and even visited Rome; Clauberg had spent time in England and may have passed the aphorism on to others), or from a correspondent (Newton’s optical theories were criticised by two French Jesuits so Catholic Scholastics were in communication with English natural philosophers).
I also found an earlier version of the phrase known as Occam’s Razor, so while Hooke can still claim priority for its use in English and in science, Punch can no longer do so for it in Latin. Roger Ariew (“DID OCKHAM USE HIS RAZOR?”, Franciscan Studies Vol. 37, (1977), pp. 5-17) cites work of H. S. Matsen (1974) on Alessandro Achillini. In Achillini’s De distinctionibus (Venetiis, 1510) he uses the criticism, “…quia multipicantur entia sine necessitate.” The same article also outlines why the metaphysical principle would not have appealed to William of Occam himself. Occam would cut hypotheses, not entities. “Ockham’s Razor, in the senses in which it can be found in Ockham himself, never allows us to deny putative entities; at best it allows us to refrain from positing them in the absence of known compelling reasons for doing so. In part, this is because human beings can never be sure they know what is and what is not ‘beyond necessity'” (SEP).