Authors/Ockham/Summa Logicae/Book II/Chapter 22

Latin	English
[2.22. DE CONVERSIONE PROPOSITIONUM DE INESSE, QUAE SUNT DE PRAETERITO ET FUTURO]	Chapter 22. On the Conversion of Past-Tense and Future-Tense Propositions of Inherence.
Circa conversionem propositionum de praeterita et de futuro est primo sciendum quad quaelibet propositio de praeterito et de futuro, in qua subicitur terminus communis, est distinguenda penes tertium modum aequivocationis', eo quod subiectum potest supponere pro eo quod est vel pro eo quod fuit, si sit propositio de praeterito; hoc est eo quod subiectum potest supponere pro eo de quo verificatur subiectum per verbum de praesenti, vel pro eo de quo verificatur subiectum per verbum de praeterito.	Regarding the conversion of propositions about the past and the future, it must first be known that any proposition about the past and the future, in which a common term is the subject, must be distinguished according to the third mode of equivocation, because the subject can supposit for that which is or for that which was, if it is a proposition about the past; this is because the subject can supposit for that of which the subject is verified by a verb about the present, or for that of which the subject is verified by a verb about the past.
Sicut ista 'album fuit Sortes' est distinguenda, eo quod 'album' potest supponere pro eo quod est album vel pro eo quod fuit album. Si autem sit propositio de futuro, tunc est distinguenda, eo quod subiectum potest supponere pro eo quod est vel pro eo quod erit, hoc est pro eo de quo verificatur subiectum per verbum de praesenti vel pro eo de quo verificatur subiectum per verbum de futuro. Et est ista regula intelligenda quando subiectum supponit personaliter, hoc est significative.	For example, 'a white thing was Socrates' is to be distinguished, because 'white' can supposit for what is white or for what was white. But if it is a proposition about the future, then it is to be distinguished, because the subject can supposit for what is or for what will be, that is, for that of which the subject is verified by a verb about the present or for that of which the subject is verified by a verb about the future. And this rule is to be understood when the subject supposits personally, that is, significatively.
Secundo sciendum quod quando subiectum talis propositionis supponit pro eo quod est, tunc illa propositio debet converti in propositionem de praesenti, accepto subiecto cum hoc verbo 'fuit' et hoc pronomine 'qui', et non in propositionem de praeterito. Unde ista consequentia non valet 'nullum album fuit homo, igitur nullus homo fuit albus', si subiectum antecedentis sumatur pro eo quod est. Nam ponatur quod multi homines, tam vivi quam mortui, fuerint albi, et quod multa alia fuerint alba et modo sint, et quod nullus homo sit modo albus, tunc est antecedens verum et consequens falsum, nam haec est vera 'nihil quod est album fuit homo', quia quaelibet singularis est vera, per casum; sed haec est falsa 'nullus homo fuit albus', qualitercumque subiectum accipiatur.	Secondly, it should be known that when the subject of such a proposition supposits for that which is, then that proposition must be converted into a proposition about the present, taking the subject with this verb 'was' and this pronoun 'who', and not into a proposition about the past. Hence this consequence is not valid: 'no white man was, therefore no man was white', if the subject of the antecedent is taken for that which is. For let it be assumed that many men, both living and dead, have been white, and that many others have been white and are now, and that no man is now white, then the antecedent is true and the consequent false, for the latter is true 'nothing that is white was a man', because any singular is true, by chance; but the latter is false 'no man was white', however the subject is taken.
Et ideo non debet praedicto modo converti, sed sic 'nullum album fuit homo, igitur nullus qui fuit homo est albus'. Et eodem modo sequitur e converso 'nullus qui fuit homo est albus, igitur nullum album fuit homo', subiecto consequentis supponente pro his quae sunt alba et non pro his quae fuerunt alba. Si autem subiectum in tali propositione accipiatur pro eo quod fuit, sic est simpliciter convertibilis in illam de praeterito et non in illam de praesenti. Bene enim sequitur 'nullum album fuit homo', subiecto accepto pro eo quod fuit, 'igitur nullus homo fuit albus'; et hoc si subiectum consequentis accipiatur pro eo quod fuit. Impossibile enim est quod aliquis homo fuerit albus et tamen quod nihil quod fuerit album fuerit homo.	And therefore it should not be converted in the aforementioned way, but thus 'no white thing was a man, therefore nothing that was a man is white'. And in the same way it follows conversely 'no one who was a man is white, therefore no white thing was a man', with the subject of the consequent suppositing for those things that are white and not for those that were white. But if the subject in such a proposition is taken for that which was, then it is simply convertible into that of the past and not into that of the present. For it follows well that 'no white thing was a man', with the subject taken for that which was, 'therefore no man was white'; and this if the subject of the consequent is taken for that which was. For it is impossible that any man was white and yet that nothing that was white was a man.
Si autem talis propositio de praeterito fuerit singularis, in qua subicitur pronomen demanstrativum sine addito vel nomen proprium, tunc convertitur in propositionem singularem vel universalem, sive particularem vel indefinitam, subiecto consequentis accepto pro eo quod fuit. Sicut bene sequitur 'Sortes non fuit albus, igitur nihil quod fuit album fuit Sortes'. Sed subiecto consequentis accepto pro eo quod est, non valet consequentia. Non enim sequitur 'Sortes non fuit albus, igitur nihil quod est album fuit Sortes'; nec etiam sequitur illa de praesenti, scilicet ista 'nullum album est Sortes', nam posito quod Sortes nunc primo sit albus, ista est vera 'Sortes non fuit albus'; et utraque illarum est falsa.	But if such a proposition about the past is singular, in which a demonstrative pronoun without an addition or a proper noun is the subject, then it is converted into a singular or universal proposition, or particular or indefinite, with the subject of the consequent taken for that which was. As it follows well, 'Socrates was not white, therefore nothing that was white was Socrates'. But with the subject of the consequent taken for that which is, the consequence is not valid. For it does not follow, 'Socrates was not white, therefore nothing that is white was Socrates'; nor does that follow about the present, namely, that 'nothing white is Socrates', for supposing that Socrates is now first white, that is true 'Socrates was not white'; and both of them are false.
Est etiam notandum quod sicut propositio talis distinguitur quando subiectum est terminus communis, ita etiam potest distingui quando ponitur pronomen demonstrativum cum termino communi. Unde haec est distinguenda 'hoc album fuit Sortes', eo quod potest esse implicatio mediante verbo de praesenti, et tunc est iste sensus 'hoc, quod modo est album, fuit Sortes', vel mediante verbo de praeterito, ut iste sit sensus 'hoc, quod fuit album, fuit Sortes'. Et est talis propositio convertibilis uniformiter propositioni de praeterito in qua subicitur terminus communis.	It should also be noted that just as such a proposition is distinguished when the subject is a common term, so it can also be distinguished when a demonstrative pronoun is placed with a common term. Hence this is to be distinguished 'this white thing was Socrates', because it can be implied by means of a verb of the present, and then the sense is 'this, which is now white, was Socrates', or by means of a verb of the past, so that the sense is 'this, which was white, was Socrates'. And such a proposition is uniformly convertible to a proposition of the past in which a common term is the subject.
Illa quae dicta sunt de propositione de praeterita applicanda sunt, proportionaliter, propositioni de futuro, iuxta distinctianem prius datam.	What has been said about a proposition about the past must be applied, proportionally, to a proposition about the future, according to the distinction given previously.
Sciendum est etiam quod, sicut dictum est prius, quod in propositionibus de praesenti adverbialis determinatio addenda est in consequente participio prioris verbi et non verbo; ita est faciendum in illis de praeterito et de futuro.	It should also be noted that, as was said before, in propositions about the present the adverbial determination must be added to the consequent participle of the preceding verb and not to the verb; the same must be done in those about the past and the future.
Per praedicta patet quod tales consequentiae non valent 'Deus non semper fuit creans, igitur creans non fuit semper Deus', nam antecedens est verum, hoc scilicet 'Deus non fuit semper creans', quia non fuit creans ante mundi creationem; sed haec est falsa 'creans non semper fuit Deus', quia hoc creans semper fuit Deus. Sicut enim haec est vera 'album fuit nigrum' et tamen haec numquam fuit vera 'album est nigrum', ita haec est vera 'creans semper fuit Deus' et tamen haec non fuit semper vera 'creans est Deus';	From the above it is clear that such consequences are not valid as 'God was not always creating, therefore the creator was not always God', for the antecedent is true, namely 'God was not always creating', because he was not the creator before the creation of the world; but the latter is false 'the creator was not always God', because this creator was always God. For just as this is true 'a white thing was black' and yet this 'white is black' was never true, so this is true 'the creator was always God' and yet this 'God is a creator' was not always true;
et ideo praedicta consequentia non valet. Sed debet sic converti 'Deus non fuit semper creans, igitur nihil quod fuit semper creans, est Deus', vel 'nihil quod semper fuit creans, fuit Deus'. Et ista est vera, quia habet duas causas veritatis: vel quia nihil semper fuit creans; vel quia aliquid semper fuit creans, quod tamen non est Deus. Et prima causa est vera, quamvis secunda sit falsa. Similiter ista consequentia non valet 'nullus videns fuit caecus, igitur nullus caecus fuit videns', accepto subiecto antecedentis pro eo quod est; sed debet sic converti 'igitur nullus qui fuit caecus, est videns'. Et ita propositio de praeterito, accepto subiecto pro eo quad est, convertitur in unam de praesenti, modo praedicto, sicut quando subiectum accipitur pro eo quod fuit, convertitur in illam de praeterito, subiecto consequentis accepto pro eo quod fuit.	and therefore, the aforementioned consequence is not valid. But it should be converted thus: 'God was not always creating, therefore nothing that was always creating is God', or 'nothing that was always creating was God'. And this is true, because it has two causes of truth: either because nothing was always creating; or because something was always creating, which nevertheless is not God. And the first cause is true, although the second is false. Similarly, this consequence is not valid 'no seeing person was blind, therefore no blind person was seeing', taking the subject of the antecedent for what is; but it should be converted thus 'therefore no one who was blind is seeing'. And thus a proposition from the past, taking the subject for what it is, is converted into one from the present, in the aforementioned way, just as when the subject is taken for what it was, it is converted into that from the past, with the subject of the consequent taken for what it was.
Similiter est de talibus 'nullum impossibile erit verum'; si subiectum accipiatur pro eo quod est, convertitur in unam de praesenti, scilicet sic 'nullum impossibile erit verum, igitur nihil quod erit verum est impossibile'; si subiectum accipiatur pro eo quod erit, convertitur sic 'igitur nullum verum erit impossibile', subiecto consequentis accepto pro eo quod erit.	Similarly, it is the case with such statements as 'nothing impossible will be true'; if the subject is taken for what is, it is converted into one of the present, namely thus 'nothing impossible will be true, therefore nothing that will be true is impossible'; if the subject is taken for what will be, it is converted thus 'therefore nothing true will be impossible', with the subject of the consequent taken for what will be.
Sciendum est etiam quod quando talis propositio de praeterito est vel de futuro, si subiectum sit terminus communis vel includens terminum cammunem cum pronomine demonstrativo et praedicatum sit pronomen demonstrativum sine addito vel nomen proprium, tunc si subiectum accipiatur pro eo quod est, convertitur in illam de praesenti, sine omni alia variatione. Sicut sequitur 'album erit Sortes, igitur Sortes est albus', sed non e converso est mutua canuersio, et hoc si sit possibile dare ultimum rei permanentis in esse. Similiter bene sequitur 'aliquod album fuit Sortes', subiecto accepto pro eo quod est, 'igitur Sortes est albus', sed non sequitur e converso, si sit dare primum rei permanentis in esse. Si autem subiectum accipiatur pro eo quod erit vel fuit, convertitur absolute in illam de praeterito vel de futuro, et est mutua conversio.	It should also be noted that when such a proposition is about the past or about the future, if the subject is a common term or includes a term that is common with a demonstrative pronoun and the predicate is a demonstrative pronoun without an addition or a proper noun, then if the subject is taken for what is, it is converted into a proposition about the present, without any other variation. As it follows, 'a white thing will be Socrates, therefore Socrates is white', but not vice versa, there is a mutual conversion, and this if it is possible to give the ultimate of a thing permanent in being. Similarly, 'some white thing was Socrates' follows well, with the subject taken for what is, 'therefore Socrates is white', but it does not follow vice versa, if it is to give the first of a thing permanent in being. But if the subject is taken for what it will be or was, it is converted absolutely into that about the past or the future, and there is a mutual conversion.