Universa Philosophia

Opposition is the repugnance of two propositions in truth or falsity (that is) there are two propositions to which falsity together, or truth together, is repugnant. I have omitted the opposition of propositions according to quantity, because they are not truly opposed, but rather one is as it were a part of the other, e.g. omnis homo currit, aliquis homo currit. The first, because it is universal, contains the second under itself, because it is particular; indeed the truth of universals is adequately made up from the truth of all singulars, whether they are known confusedly or clearly. But they are said to be opposed in quantity, for I have already shown that being universal, particular, etc., is called by dialecticians the quantity of the proposition; and just as in a corporeal thing the large and the small are opposed, so metaphorically these propositions are said to be opposed according to quantity, because one is as it were small, the other as it were large.

Opposition can obtain between two universal propositions, the one affirmative, the other negative, of the same predicate concerning the same subject, as omnis homo currit, nullus homo currit, which opposition Aristotle, On Interpretation bk. 1, ch. 5, calls contrary. In another way a universal proposition and a particular one can be opposed, the one affirmative and the other negative, of the same predicate concerning the same subject, which opposition they commonly call contradictory. Some define this as the opposition of two propositions according to quantity and quality, of which one is universal, the other particular. This definition is gathered from Peter of Spain, bk. 1, ch. 11; but it is defective and not Aristotelian. For Aristotle in that ch. 5 defined it thus: I say that affirmation and negation are opposed contradictorily when the one signifies universally and the other not universally. By this definition there seems to be included the opposition between a universal and a singular proposition, which on this definition is a contradiction, as omnis homo currit, Petrus non currit; and it is proved, because if a singular known confusedly, opposed to a universal proposition and affected by a particular or indeterminate sign, aliquis, is opposed contradictorily to a universal proposition, why will the same singular, clearly and distinctly known, not be opposed for the same reason? Especially since the truth of a confused proposition is weighed by the thing itself in one determinate singular. For this proposition, aliquis homo currit, takes its truth from Peter alone running, wherefore it is opposed contradictorily to this, nullus homo currit; therefore likewise this, Petrus currit, because it takes its truth from the same source, will be opposed contradictorily to the same universal negative. Hence it seems clear that that definition is illegitimate, and that one must stand by the Aristotelian one.

But Aristotle by the examples adduced in that chapter excludes from the definition of contradiction the opposition between universal and singular: the reason is at hand, because either can be false, as omnis homo currit is false when Peter is not running, and Antonius non currit is false when Antony is running; but both can be at once, both Peter not running and Antony running. Hence it is clear that all the precepts of contradiction do not fit this opposition. To the other reason. It is answered that a confused proposition is opposed contradictorily to a universal, because it ranges over all individuals confusedly; for its falsity one individual does not suffice, as aliquis homo non currit is not false because Antony is not running, as Antonius non currit is, because it is concerned with him in the singular; but the law of contradictories depends on the clear or obscure mode of conceiving: whence Peter obscurely and vaguely known does not make a particular proposition false as he makes a singular one false when he is clearly known. But this opposition can be reduced to the contrary, because they have repugnance in truth alone and not in falsity; indeed by reason of that contrariety they do not have opposition in falsity, as I shall show in the following section. Aristotle himself in ch. 6 added that two singular propositions opposed in quality concerning the same subject and predicate are contradictory, as Socrates est albus, Socrates non est albus. Whence contradictory opposition is defined as the repugnance of two propositions according to quality, of which the one is affirmative and the other negative. Likewise the one universal, the other particular, or both singular.

P. Fonseca and the Conimbricenses deny subcontrary opposition (that is) that which obtains between two particular or confused propositions contained under contrary propositions, as are these, aliquis homo currit, aliquis homo non currit, which are contained under these universals, omnis homo currit, nullus homo currit. They are moved first: because Aristotle does not mention that opposition. Second, because they are not opposed in truth. But the common opinion is that they are opposed, as the Summulists commonly teach with Peter of Spain above. It is proved a priori, both because they are opposed according to quality—for falsity, which is repugnant to each, pertains to the property of a proposition as much as truth does—therefore just as contraries are opposed because truth is repugnant to each, so subcontraries are opposed because falsity is repugnant to each; and because I shall now show that their falsity is repugnant, since under them are contained two contradictory singular propositions, whence they have contradictory opposition, no otherwise than contraries have it. To the first I answer that Aristotle was capable of forgetfulness or ignorance. To the second I answer that it suffices that they be opposed in the other species of quality.