Authors/Ockham/Summa Logicae/Book III-1/Chapter 17

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Latin English
[Cap. 17. De syllogismis ex propositionibus de praeterito et de futuro in prima figura] [Chapter 17.  Of syllogisms from propositions of the past and future, in the first figure]
Iam visum est qualiter syllogizandum est ex propositionibus de praesenti et de inesse; nunc videndum est quomodo est syllogizandum ex propositionibus de praeterito et de futuro. Now we have looked at how we should syllogise from assertoric and present tense propositions, we must now look at how we should syllogise from past and future tense propositions.
Unde sciendum est quod quando medius terminus est terminus communis, si subiectum maioris supponit pro his quae sunt, minor debet esse de praesenti et non de futuro nec de praeterito. Nam si minor propositio esset de praeterito et non de praesenti, non regularetur talis syllogismus per dici de omni vel de nullo, quia in maiore universali de praeterito subiecto, supponente pro his quae sunt, non denotatur quod de quocumque dicitur subiectum per verbum de praeterito quod de eodem dicatur vel removeatur praedicatum per verbum de praeterito, sed denotatur quod de quocumque dicitur subiectum per verbum de praesenti quod de eodem dicatur praedicatum vel removeatur per verbum de praeterito. Hence, you should know that when the middle term is a common term, if the subject of the major supposits for things which exist [now], the minor should be in the present tense, and not in the future or the past.  For if the minor proposition were in the past and not the present tense, such a syllogism would not be governed by dici de omni, for in the major universal of a past subject, suppositing for things which exist now, it is not denoted that of whatever the subject is predicated using a verb in the past tense, the predicate is also predicated or denied using a verb in the past tense, but rather it is denoted that of whatever the subject is predicated using a verb in the present tense, the predicate is also predicated or denied using a verb in the past tense.
Et ideo sumendo sub minorem de praeterito, non arguitur per dici de omni vel de nullo, sed sumendo sub minorem de praesenti, arguitur per dici de omni vel de nullo. Unde sic arguendo ‘omne album fuit Sortes; - si album supponat praecise pro his quae sunt alba -; Plato fuit albus; ergo Plato fuit Sortes’ non valet, sed est fallacia accidentis et etiam fallacia figurae dictionis. Sed sic arguendo ‘omne album fuit Sortes; Plato est albus; ergo Plato fuit Sortes’ est bonus syllogismus, regulatus per dici de omni. And therefore, by subsuming a past tense minor, we do not argue by dici de omni, although by subsuming a present tense minor, we do.  Hence, in arguing "every white thing was Socrates (if 'white thing' supposits precisely for things which are white), Plato was white, therefore Plato was Socrates" it is not valid, but is a fallacy of accident and also a fallacy of 'figure of speech'.  But in arguing "every white thing was Socrates, Plato is white, therefore Plato was Socrates" it is a good syllogism, governed by dici de omni.
Si autem subiectum maioris supponat pro his quae fuerunt, tunc non debet accipi sub minor de praesenti, quia sicut manifeste patet, non arguitur per dici de omni vel de nullo; sed debet sumi sub minor de praeterito, et non refert sive subiectum minoris supponat pro his quae sunt sive pro his quae fuerunt. But if the subject of the major supposits for things which used to exist, then a present tense minor should not be subsumed, for, as is manifestly clear, we are not arguing by dici de omni.  Rather, we should subsume a past tense minor, and it does not matter whether the subject of the minor supposits for things which exist, or for things which used to exist.
Unde iste syllogismus non valet ‘omne album fuit homo; asinus est albus; igitur asinus fuit homo’. Ponatur enim quod nihil fuerit album ante nunc nisi homo et quod multi asini sint modo albi, tunc haec est vera 'omne album fuit homo' sub hoc > sensu ‘omne quod fuit album, fuit homo’; et haec etiam est vera ‘asinus est albus’ et haec est falsa ‘asinus fuit homo’. Sed iste syllogismus est bonus ‘omne album fuit homo; asinus fuit albus; igitur asinus fuit homo’, et regulatur per dici de omni. Hence the syllogism "every white thing was a man, a donkey is white, therefore a donkey was a man" is not valid.  For suppose that nothing was white before now except a man, and that many donkeys are now white, then "every white thing was a man" is true, in the sense that everything that was white, was a man, and also "a donkey is white", but "a donkey was a man" is false.  But the syllogism "every white thing was a man, a donkey was white, therefore a donkey was a man" is valid, and is governed by dici de omni.
Ex istis potest patere solutio aliquorum sophismatum quae peccant per fallaciam figurae dictionis, puta talium ‘quidquid fuit homo, hodie est animal; aliquod album fuit homo; igitur aliquod album hodie est animal’; ‘quidquid vidisti, hodie tetigisti; album vidisti; igitur album hodie tetigisti’. Unde ad videndum an sit fallacia figurae dictionis et fallacia accidentis in talibus, videndum est an subiectum minoris supponat pro his quae sunt, et tunc est fallacia accidentis; vel pro his quae fuerunt, et tunc non est fallacia, sed regulatur per dici de omni, vel potest reduci in talem syllogismum per expositionem propositionum. And from this the solution is clear to some of the sophismata which err by the fallacy of 'figure of speech', for example "whatever was a man, today is an animal, something white was a man, therefore something today is an animal"; "whatever you have seen, today you have touched, you have seen a white thing, therefore you have touched a white thing today".  Hence, for seeing whether there is a fallacy of 'figure of speech' or a fallacy of accidents in such cases, it must be seen whether the subject of the minor supposits for things which exist, and then it is a fallacy of accident, or for things which used to exist, and then it is not a fallacy, but is governed by dici de omni
Ista quae dicta sunt de propositionibus de praeterito, proportionaliter sunt servanda circa propositiones de futuro. Nam si subiectum maioris accipiatur pro his quae erunt, minor debet esse de futuro; si accipiatur pro his quae sunt, minor debet esse de praesenti. What has been said about propositions of the past tense, can correspondingly be kept of propositions of the future tense.  For if the subject of the major is accepted for things which will exist, the minor ought to be in the future tense.  If it is accepted for things which exist now, the minor ought  to be in the present tense.
Est etiam intelligendum quod quando maior est de praesenti, numquam minor debet esse de praeterito vel de futuro, nisi a parte subiecti maioris exprimatur verbum de praeterito vel de futuro; et tunc minor debet esse singularis, vel subiectum debet accipi pro eo quod est, et hoc sive subiectum sit terminus communis sive sit pronomen demonstrativum cum termino communi sumptum. Si enim subiectum accipiatur pro eo quod fuit, non valet discursus; sicut non sequitur ‘omne, quod fuit album, est homo; nigrum fuit album; ergo nigrum est homo’, et est fallacia accidentis in talibus. Quando tamen in talibus est fallacia figurae dictionis, patebit inferius[1].
Propter protervos vero est intelligendum quod quamvis talis propositio sit vera ‘Sortes fuit albus’, quamvis Sortes non sit, tamen tali discursus est bonus ‘quidquid fuit album est animal; Sortes fuit albus; > igitur Sortes est animal'. Tamen sic arguendo ‘quilibet homo, qui fuit albus, est animal; Sortes fuit albus; igitur Sortes est animal’ non tenet, et hoc quia in ista ‘quilibet homo, qui fuit albus, est animal’ li homo non supponit pro his quae sunt homines. Haec dicta sunt de talibus syllogismis in prima figura.


Notes

  1. Infra, in tractatu De fallaciis, c. 10.
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