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Published online by Cambridge University Press: 13 April 2010
An obligation, in the sense in which it was of interest to medieval logicians from about the early thirteenth century to the end of the scholastic period, is, according to Paul of Venice, a relation limiting one to take some statement affirmatively or negatively. This relation is based on the actions of two individuals: one (the opponent) obligates the other (the respondent) by first putting forward a sentence which the respondent agrees to affirm or deny for a limited time. The sentence the respondent agrees to affirm is called the positum; that which he agrees to deny, the depositum; and his act of agreeing, the admissio. After this relation is established between the opponent and respondent, the opponent proceeds by putting forward a series of sentences to which the respondent replies by granting, denying, or doubting — all in accordance with certain rules the two individuals have previously accepted as governing their exchange. If the respondent at any time grants what is inconsistent with the sentence he agreed to uphold, or responds in a way that violates the accepted rules, the exchange comes to an end. The respondent has failed in his obligation.
1 See Stump, Eleonore, chap. 16, “Obligations: A. From the Beginning to the Early Fourteenth Century,” in Kretzmann, Norman, Kenny, Anthony and Pinborg, Jan, eds., The Cambridge History of Later Medieval Philosophy (Cambridge: Cambridge University Press, 1982), p. 315.CrossRefGoogle Scholar
2 Paul argues for this informal definition in his Logica Magna. See Paul, of Venice, Logica Magna, Part II, Fascicule 8, edited by Ashworth, E. Jennifer (Oxford: Oxford University Press, for the British Academy, 1988), p. 7.Google Scholar This definition differs from the one Paul gives in his Logica Parva, an earlier work (Paulus Venetus, Logica Parva, translated by Alan R. Perreiah [Washington, DC: Catholic University of America Press, 1984]); see p. ix of Ashworth's introduction to Paul of Venice's Logica Magna. Ashworth says that Paul's definition of obligations in terms of relation (one of Aristotle's 10 categories) appears to be original with him (see p. 7, n. 5, of Paul of Venice, Logica Magna).
3 Paul of Venice, Logica Magna, p. 6–14.
4 Richard Billingham, for example, thought that an obligation could be construed either as an art by means of which an opponent can bind a respondent to reply at the opponent's pleasure to an obligatory sentence put to him, or as a sentence someone agrees to uphold by affirming or denying: “Obligatio est quaedam ars mediante qua aliquis opponens potest ligare respondentem ut ad suum bene placitum respondeat ad obligationem sibi positum; vel obligatio est oratio mediante qua aliquis obligatus tenetur affirmative vel negative ad obligationem respondere.” This quotation from Billingham's Ars obligatoria, MS Salamanca, Bib. Univ. 1735, fols. 89r-95v, is taken from E. J. Ashworth's “English Obligationes Texts after Roger Swyneshed: The Tracts beginning ‘obligatio est quaedam ars’,” in P. Osmund Lewry, ed., The Rise of British Logic (Toronto: Pontifical Institute of Mediaeval Studies, 1985), p. 309.
5 See Boehner, Philotheus's-Medieval Logic: An Outline of its Development from 1250 to c. 1400 (Manchester: Manchester University Press, 1952).Google Scholar
6 Ibid., p. 14–15.
7 Spade, Paul Vincent, “Three Theories of Obligationes: Burley, Kilvington and Swyneshed on Counterfactual Reasoning,” History and Philosophy of Logic, 3 (1982): 2, n. 3.Google Scholar
8 Ibid., p. 2.
9 I will say more later about the notion of irrelevance. See p. 479–80 below.
10 Weisheipl, James A., “Developments in the Arts Curriculum at Oxford in the Early Fourteenth Century,” Mediaeval Studies, 28 (1966): 163–64.CrossRefGoogle Scholar
11 Romuald Green, The Logical Treatise “De obligationibus”: An Introduction with Critical Texts of William of Sherwood (?) and Walter Burley, 2 vols. (St. Bonaventure, NY: Franciscan Institute, forthcoming), as quoted by Spade in “Three Theories,” p. 2, n. 4.
12 Perreiah, Alan, “Obligationes in Paul of Venice's Logica Parva,” Analecta Augustiniana, 45 (1982): 113.Google Scholar
13 Spade, “Three Theories,” p. 2.
14 Ibid. See especially the abstract and conclusion on p. 1 and 31–32, respectively.
15 E.g., Walter Burley and Roger Swyneshed, whose views were at the centre of the controversy mentioned above on p. 475. See Stump, Eleonore, “Roger Swyneshed's Theory of Obligations,” Medioevo, 7 (1981): 169–74.Google Scholar
16 Ibid., p. 172.
17 Stump, “Obligations,” p. 332. (On p. 315 Stump says, “My own account of obligations will emerge in the course of this chapter.”) Although in part of the passage I do not cite, Stump claims that in Richard Kilvington's Sophismata (written around 1325) “the whole purpose of obligations” is shifted “towards a logic of counterfactuals,” it seems clear from her later criticism of Spade's account of obligations that she changed her mind about this.
18 Stump, “Roger Swyneshed's Theory of Obligations,” p. 172–73.
19 Ashworth, Introduction to Logica Magna, p. xiii–xiv. In this summary of ways in which obligations have been characterized I have not mentioned the one in which obligations turn out to be mere games. See Angelelli, Ignacio, “The Techniques of Disputation in the History of Logic,” Journal of Philosophy, 67 (1970): 802–3zCrossRefGoogle Scholar; and de Rijk, L. M., “Some Thirteenth Century Tracts on the Game of Obligation,” Vivarium, 12 (1974): 95.CrossRefGoogle Scholar
20 For references, see p. 33, n. 3 of E. J. Ashworth's edition of Paul of Venice's Logica Magna. To the authors cited, one should add the author of Obligationes Parisienses, who wrote almost two centuries before Paul of Venice and distinguishes between disputations whose aim is knowledge or truth and disputations whose aim is “exercise or being exercised” (exercitatio sive esse exercitatum). See p. 26–27 of de Rijk, L. M.'s “Some Thirteenth Century Tracts on the Game of Obligation,” Vivarium, 13, 1 (1975).CrossRefGoogle Scholar
21 It is worth noting that Ashworth, in her Introduction to Logica Magna, says that whatever the final answer is to questions about the function of obligational disputations, “reading Paul of Venice should help us to arrive at it, since his Tractatus de Obligationibus is a compendium of all the main views current in the second half of the fourteenth century” (p. xiv). According to Ashworth, Paul's sources were primarily Albert of Saxony (d. 1390), William Buser (fl. 1360), Ralph Strode (fl. 1360), Peter of Candia (d. 1410) and some version of the Logica Oxoniensis (p. xii).
22 Paul of Venice, Logica Magna, p. 32: “Secunda suppositio est ista: Quod omnes regulae superius adsignatae in Tractatu Consequentiarum de consequentia bona vel non bona sunt hic fundamentaliter sustinendae. Et ratio quia materia obligationum non est nisi materia consequentiarum stilo subtiliori procedens, et an respondens sit sani capitis gressu deceptorio temptativa; nam per huiusmodi casus obligationis, sive veri sint sive falsi, stabilem sustentationem docetur infallibiliter et invariabiliter sustinere. Quare iam causam finalem huius artis verus indagator poterit adsignare.”
Throughout this paper, translations of passages from Logica Magna are my own.
Some might take the last sentence in the passage to suggest that according to Paul there is more to the purpose of obligations than “testing whether the respondent has a good head.” But it would be surprising indeed for Paul – in what Ashworth described as a compendium of all the main views current in the second half of the fourteenth century” (in Paul of Venice, Logica Magna, p. xiv) – to take the time to state the simplest aim of obligations and not bother to mention at least one of the more subtle and complicated aims of which the genuine investigator would surely want to be apprised. A more plausible reading of that last sentence is that the genuine investigator of obligations now knows what the aim of obligations is because Paul has just told him.
23 Ibid., p. 36ff.
24 Ibid., p. 48: “De prima specie obligationis non procedam in sequentibus, nisi forte de per accidens ratione positionis vel depositionis, quia non est oratio temptativa nec per quam fit disputatio deceptoria, sed sola positio vel depositio est huiusmodi.” In the case of suppositio, the respondent is asked to grant a suppositum as true, necessary, or known per se. For example, if the opponent says, “I assume that Antichrist exists,” once the respondent admits this, he is obligated to defend the truth of the sentence ‘Antichrist exists’ for the duration of the disputation. (See p. 36.)
25 Spade thinks that the fact that “except for the disputations given solely for illustrative purposes in [treatise on obligations], not a single disputatio de obligationibus seems to have been preserved,” indicates that such disputations did not take place. See his introduction to “Roger Swyneshed's Obligationes: Edition and Comments,” Archives d'Histoire Doctrinale et Littéraire du Moyen Âge, 44 (1977): 245Google Scholar. That such disputations actually took place, however, seems clear enough when, for example, Paul of Venice states that an obligational disputation could come to an end if there were a “disturbance … as often happens,” or if one of the participants died (si opponens vel respondens infra disputationem desineret esse). See Logica Magna, p. 20–24.
26 Consider, for example the various solutions which have been produced regarding the truth-value of self-referential sentences. See Spade, Paul Vincent, The Mediaeval Liar: A Catalogue of the Insolubilia Literature (Toronto: Pontifical Institute of Mediaeval Studies, 1975)Google Scholar.
27 See p. 477 above, and note 20.
28 See Stump, “Obligations,” p. 316–17.
29 It is called this by Robert Fland in the mid-fourteenth century. See Spade, Paul Vincent, “Robert Fland's Obligationes: An Edition,” Mediaeval Studies, 42 (1980): para. 13 and 20, and Spade, “Obligations,” p. 335.CrossRefGoogle Scholar
30 Paul included under the heading of positio everything that Burley included under the headings of positio, petitio, sit verum, dubitatio and institutio. See Logica Magna, Part I, p. 38–40. There would seem to be no place in Paul's scheme for dubitatio, however. For example, he says that an obligation is a relation through which someone takes a statement affirmatively or negatively (Logica Magna, p. 6). Yet in dubitatio the statement admitted at the outset of the disputation is taken as uncertain or of unknown truth-value. Much later Paul adds, “What has been said about positio indicates what must be said about depositio since opposite species are described in an opposite way with respect to all their essential characteristics. However, for greater clarity [I will give some rules].” (See Logica Magna, Part III, p. 368–76.)
31 Spade, “Roger Swyneshed's Obligationes, p. 246. Swyneshed's treatise was written roughly between 1330 and 1335.
32 Spade, “Robert Fland's Obligationes,” para. 14 and 20, and Spade, “Obligations,” p. 335–36. Fland's treatise was written between 1335 and 1370.
33 Swyneshed's words are the following: “Omne sequens ex posito sine obligatione ad hoc pertinente non repugnans positioni in tempore obligationis est concedendum. … Omne repugnans posito sine obligatione ad hoc pertinente non repugnans positioni in tempore positiones est negandum” (in Spade, “Roger Swynshed's Obligationes,” p. 266, secs. 67 and 68). And “Nulla propositio impertinens scita ab aliquo sibi principaliter significare sicut est est neganda sine obligatione ad hoc pertinente nec scita significare principaliter aliter quam est est concedenda, nec scita significare principaliter dubie est neganda vel concedenda” (ibid., p. 256–57, sec. 31).
34 Swyneshed's words are the following: “Propter concessionem partium copulativae non est copulativa concedenda nec propter concessionem disjunctivae est aliqua pars eius concedenda” (ibid., p. 257, sec. 32). One should notice that the first corollary is logically deviant while the second is not. The expected correspondingly deviant corollary would be ‘(B') One need not grant a disjunction in virtue of having granted any of its disjuncts’.
35 “Ultima regula est ista: Qualibet parte copulativae concessa, concedenda est copulativa cuius illae vel consimiles sunt partes principales. … Sed quia aliqui tenent oppositum huius regulae quasi omnes antiqui, ideo pro maiori regulae declaratione arguo contra eos primo sic …” (Logica Magna, p. 68).
36 Ibid., p. 68–70.
37 In “The Problems of Relevance and Order in Obligational Disputations: Some Late Fourteenth Century Views,” Medioevo, 7 (1981): 187Google Scholar, E. J. Ashworth approvingly quotes the following statement that Paul makes at the end of his evaluation of this first mock disputation: “The whole reason why this conjunction [i.e., “Either no man is in Rome or you are not a man, but you are a man”] should be denied is because it is false by reason of one false part, and it is irrelevant because it neither follows from its parts nor is incompatible with them, as this opinion [Swyneshed's] says. But this is not the case here [re the conjunction at step (3)], for this last-formed conjunction is irrelevant, as this opinion must say, but it is true because each of its parts is true. Therefore, it is to be conceded, and thus there is no escape.” (See Logica Magna, p. 70 for the Latin text.)
Two things need to be said about this. First, as I point out (see p. 481–82 above), the respondent who accepts Swyneshed's new rules may very well grant the conjunction at step (3) for the reason that it is irrelevant and true. Yet this fact does not count against Swyneshed's rules. That is, there is an escape.
Second, Ashworth seems to quote Paul at least in part in an attempt to show how a follower of Swyneshed, Martinus Anglicus, in a mock disputation similar to the one Paul considers in his first argument against the “new response” cannot spell out precisely why on the new response one should respond in a particular way at a particular point in the disputation. But, when at the last stage of that disputation whose positum is ‘You are in Rome’ the sentence proposed is ‘Either you are not in Rome or you are not a man, and it is not the case that you are not a man’, the respondent who denies, as Martinus does, this conjunction (call it C) can do so in accordance with Swyneshed's rules, since C is incompatible with the positum in question. That is, C is not irrelevant given the new rules, even though Paul seems to think that it would be. C is not irrelevant because (∼(You are in Rome) or ∼(You are a man)) and ∼(You are not a man) implies ∼(You are in Rome). But ∼(You are in Rome) is inconsistent with the positum which is ‘You are in Rome’. Thus, even though Martinus gives as his reason for denying C “This conjunction is denied, in order to avoid accepting the conclusion, ‘You are not in Rome’,” he could have said more. So neither Paul's nor Martinus's mock disputations count against the satisfactoriness of Swyneshed's new rules of obligation.
38 Let the first positum be A, and the second B. It is clear that ∼A (the first conjunct of the conjunction at step [3]) is inconsistent with (A ∧ B), that ∼B (the second conjunct of the conjunction at step [3]) is inconsistent with (A ∧ B), and that (∼A ∧ ∼B) is inconsistent with (A ∧ B).
39 Logica Magna, p. 70–72.
40 Logica Magna, p. 70.
41 See above, p. 480, and note 34.
42 See Swyneshed's Obligationes, p. 257, sec. 32, edited by P. V. Spade in Archives d'Histoire Doctrinale et Littéraire du Moyen Âge, 44 (1977), and Richard Lavenham's Obligationes, p. 229–31, sees. 11–13, edited by P. V. Spade in Revista Critica di Storia Della Filosofia, 33 (1978).
43 “Unde illa responsio ponit tales duas regulas. Prima est: Utraque pars copulativae est concedenda, quae copulativa est neganda. Secunda est quod disjunctiva est concedenda cujus utraque pars est neganda” (Spade, “Robert Fland's Obligationes, p. 45, sec. 17). It is clear from the text that Fland takes these to be the two controversial corollaries of the “new response.” (See p. 45, sees. 13–17.)
44 Logica Magna, p. 72.
45 Ibid.
46 Ibid., p. 34: “The sixth assumption is this: Outside the time of an obligation the truth of things is to be acknowledged, because anyone who concedes what is false or denies what is true when he is not obligated to do so responds badly.” It should also be noticed that on the “old response” which was exemplified by Walter Burley, in positio the positum was always false and known to be such, yet was defended as true by the respondent; and in depositio the depositum was always true and known to be such, yet was maintained as false by the respondent. See Stump, “Roger Swyneshed's Theory of Obligations,” p. 136–37.
47 Swyneshed, in Spade, “Swyneshed's Obligationes,” secs. 37–43, p. 260–61:
“Sec. 41. Si tamen sic respondeatur contra: “In quacumque propositione falsa in qua ponitur ‘a’, ‘a’ solum significat hominem; haec est propositio falsa in qua ponitur ‘a’; igitur, in illa ‘a’ solum significat hominem,” concedenda est consequentia et negandum est antecedens pro majore et minore, quia falsum et nonsequens ex posito. Nam antecedens est una copulativa cujus utraque pars est concessa, et ex hoc non sequitur quod illa sit concedenda, sicut patet per secundam conclusionem.
“Sec. 42. Contra: Inter majorem et minorem non est nota conjunctionis media. Igitur, ibi non est copulativa.
“Sec. 43. Dicendum est quod consequentia non valet, quia licet non sit ibi nota conjunctionis media, tamen major et minor sumantur copulative, et ideo ibi est copulativa. … in argumento syllogistico major cum minore copulative sumuntur demissa nota conjunctionis eo quod evidentia ex modo et figura est satis manifesta.”
48 Ashworth, “Problems,” p. 181. See also p. 186–92, where Ashworth discusses some of the arguments of Marsilius of Inghen, Albert of Saxony and Ralph Strode against Swyneshed's corollary re conjunction. These arguments are reflected in the four unsuccessful arguments Paul presents. Therefore, the sorts of considerations which counted against Paul's arguments count against these arguments as well.
49 Spade, in “Three Theories,” and Stump, in “Roger Swyneshed's Theory of Obligations,” seem to endorse this view.
50 Logica Magna, p. 32–34.
51 That is, he will have evaluated arguments roughly of the form (positum, therefore propositum1), (positum, therefore propositum 2), (positum, therefore propositum 3), etc., rather than an argument roughly of the form (positum and [propositum 1 or not-propositum 1] and [propositum 2 or not-propositum 2] and [propositum 3 or not-propositum 3] and … therefore propositum n).
52 Spade, “Roger Swyneshed's Obligationes,” p. 273, sec. 98, and p. 275, para. 102, for example.
53 Stump, “Roger Swyneshed's Theory of Obligations,” p. 169.
54 And truth was not an issue in obligational disputations. On the distinction between the obligational disputation and what Ashworth dubs “the doctrinal disputation,” see Ashworth, E. Jennifer's “Renaissance Man as Logician: Josse Clichtove (1472–1543) on Disputation,” History and Philosophy of Logic, 7 (1986): 15–29.CrossRefGoogle Scholar
55 “Eligat igitur respondens quamcumque positionem quam voluerit et sustinetur reponsio nova novis et antiqua antiquis” (Spade, “Robert Fland's Obligationes,” p. 46, sec. 20).
