William of Sherwood

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William of Sherwood (or Shyreswood, Shireswood) (c1190 – c. 1266), was a medieval English logician and teacher.

Little is known of his life, but he is thought to have studied at the University of Paris, as a master at Oxford university in 1252, and that he was treasurer of Lincoln from 1254/8 onwards, and a rector of Aylesbury.

He was the author of two books which were an important influence on the development of Scholastic logic: Introductiones in Logicam (Introduction to Logic), and Syncategoremata. These are the first known works to deal in a systematic way with what is now called supposition theory, known in William's time as the logica moderna.


William was probably born in Nottinghamshire, between 1200 and 1210. In common with many educated English men of that time, he may have studied at the medieval Oxford university or the University of Paris, or both. There are examples in his logical work which suggest he was a master at Paris. (For example 'No man lectures at Paris unless he is an ass' / 'Whatever runs has feet, the Seine runs, ergo the Seine has feet'). Further evidence that he lectured in Paris is that those logicians who were influenced by his work also worked in Paris, such as Peter of Spain (around 1245), and Lambert of Auxerre (around 1250).

He is thought to have become treasurer of Lincoln Cathedral some time in the 1250s. The treasurer was one of the four principal officers of the English cathedrals whose duty was to keep the treasures of the church, the gold and silver vessels, ornaments, relics, jewels, and altar cloths. He would have had a personal residence in the Cathedral close, would have employed a deputy and a large staff, and therefore could be absent as long as he performed those duties that could not be delegated (source: Edwards).

He is mentioned by Roger Bacon, also a Master at Paris, as one of 'the more famous wise men of Christendom' one of whom is Albertus Magnus, another of whom is master William of Sherwood, 'the treasurer of the church of Lincoln in England, who is much wiser than Albert'. (Brewer, transl. Kretzmann).


William's main work is a small logic manual, Introductiones in logicam. It survives in a single manuscript probably written in the late thirteenth century, headed 'Introductiones Magistri Guilli. De Shyreswode in Logicam', (Bibliotheque Nationale, Cod. Lat. 16617, formerly Codex Sorbonnensis 1797). It did not appear fully in print until 1937, in Grabman's Latin edition, and was not translated into English until 1966, by Kretzmann. No other works than are definitely by him have ever been printed.

The book consists of Six Chapters. Five of these are expositions of Aristotle's main logical works, as follows: 1. 'Statements', corresponding to De Interpretatione, 2. 'The Predicables', corresponding to Categories, 3. 'Syllogism', corresponding to Prior Analytics, 4. 'Dialectical Reasoning' corresponding to Topics, and 6. 'Sophistical Reasoning' corresponding to Sophistical Refutations. However, Chapter 5, 'Properties of Terms', contains material that is not in Aristotle, but is a distinctively medieval development, (Supposition theory) that deals with the semantics of propositions. The theory attempts to explain how the truth of simple sentences, expressed schematically, depend on how the terms 'supposit' or stand for certain extra-linguistic items, and tries to address the problem of sentential forms, like 'I promise you a horse', which do not appear to fit the standard syllogistic forms.

In this chapter William introduces what was to become a standard division of supposition into 'material', 'formal' and 'personal'. In material supposition, a term stands for itself, as when we say that 'Socrates' is a name (note that medieval Latin did not use quotation marks as in modern English). In formal supposition, the word signifies its meaning, as in man is a species. Formal supposition is similar to what is indicated in modern philosophical logic by italicising a common noun, as when we refer to the concept horse. Personal supposition is approximately the relation we now call 'satisfied by', or 'denotes', as in 'the term 'man' denotes Socrates, Aristotle, &c'.

He discusses a number of problem cases. For example, the sentence 'every man sees a man' is true when there is a single man that every man sees (for example if 'every man sees Socrates' is true). But the sentence is also true when every man sees a different man, or when some men see a single man (such as Socrates), other men see another man, and innumerable cases in between. This is called 'confused' supposition. This instance of the problem of multiple generality, is now thought to be insoluble using the fixed schema of Aristotle's semantics.


William's work spurred a development of logic in the thirteenth century under the general designation De Proprietibus Terminorum. Those who engaged in this part of logic were called the Moderni, or Terministae. Its most detailed treatment is found in Ockham, and in the works of those who followed him.

Now, William is perhaps best known for a mnemonic poem to help students remember the names of the valid syllogistic forms:

Barbara celarent darii ferio baralipton
Celantes dabitis fapesmo frisesomorum;
Cesare campestres festino baroco; darapti
Felapton disamis datisi bocardo ferison

This verse may not have originated with him, but it is the oldest known surviving version. Peter of Spain later gives an account of the verses which is more detailed, and also one which lacks mistakes in William's version. According to Kretzmann, this strongly suggests their source is a single earlier version, now lost.

Primary sources


  • Introductiones in Logicam (Bibliotheque Nationale, Cod. Lat. 16617, formerly Codex Sorbonnensis 1797).


  • Grabman, M. Edition published as 'Die Introductiones in logicam des * Wilhelm von Shyreswood' in Sitzungsberichte der Bayerischen Akademie der Wissenschaften, Philosophisch-historische Klasse, Jahrgang 1937, Heft 10.

Secondary sources

  • Brewer, S.J. Preface to his edition of Bacon's Opus Tertium.
  • Edwards, K., The English Secular Cathedrals in the Middle Ages, Manchester 1949.
  • Kneale, William & Martha Kneale. Development of Logic (Oxford: Clarendon Press, 1962)
  • Kretzmann, N., 'William of Sherwood's Introduction to Logic, Minneapolis 1966.
  • Kretzmann, Norman, Anthony Kenny & Jan Pinborg. Cambridge History of Later Medieval Philosophy (Cambridge: Cambridge University Press, 1982). contains a good bibliography on p. 892.
  • "Philosophy 112, Intermediate Symbolic Logic: History of Predicate Logic" ([1])
  • Read, S., '[Medieval Theories: Properties of Terms http://plato.stanford.edu/entries/medieval-terms]'.

See also


5 1200 1235 England 1265 England