pons asinorum

From New Latin pons asinorum, from Latin pōns (“bridge”) + genitive plural of asinus (“donkey”). Literally, “bridge of donkeys”.

pons asinorum (plural pontes asinorum)

1. (logic) A method for finding the middle term of a syllogism in Aristotlean analytics. [from 17th c.]
2. An obstacle which will defeat a beginner or foolish person. [from 17th c.]
3. (geometry) A proposition in Euclid stating that the angles at the base of an isoceles triangle are equal. [from 18th c.]
   • 1751, [Tobias] Smollett, The Adventures of Peregrine Pickle […], volumes (please specify |volume=I to IV), London: Harrison and Co., […], →OCLC:

     [H]e had scarce advanced beyond the Pons Asinorum, when his ardour abated, the test of truth by demonstration did not elevate him to those transports of joy with which his preceptor had regaled his expectation; and before he arrived at the fortieth and seventh proposition, he began to yawn drearily […] .

Literally “bridge of donkeys”, attributed to Jean Buridan (14th century) but first attested in Petrus Tartaretus (d. 1522), who cites it as a common appellation for the device in syllogistic reasoning “because of its apparent difficulty”, i.e. it separates experts from “donkeys”. The application to Euclid appears to postdate its use in logic.

• (Classical) IPA^(key): /pons a.siˈnoː.rum/, [põːs̠ äs̠ɪˈnoːrʊ̃ˑ]
• (modern Italianate Ecclesiastical) IPA^(key): /pons a.siˈno.rum/, [pɔns äs̬iˈnɔːrum]

pōns asinōrum m (genitive pontis asinōrum); third declension (Medieval Latin, New Latin)

1. (logic) a method for finding the middle term in an Aristotelian syllogism, or a diagrammatic representation of this method
2. (geometry) the geometric theorem (Euclid's fifth) that the two angles opposite the equal sides of an isosceles triangle are also equal
3. (generally) a difficult early test that must be passed if further progress is to be made

Third-declension noun (i-stem) with an indeclinable portion.

• → Dutch: ezelsbrug, ezelsbruggetje (calque)
  • → Indonesian: jembatan keledai (calque)
• → Finnish: aasinsilta (calque)
• → German: Eselsbrücke (calque)
• → Hungarian: szamárhíd (calque)

• A. F. West, H. D. Thompson (1891) “On dulcarnon, elefuga and pons asinorum as fanciful names for geometrical propositions”, in The Princeton College Bulletin, volume 3, number 4, pages 86–88