Authors/Ockham/Summa Logicae/Book III-3/Chapter 38

Latin	English
CAP 38. DE REGULIS GENERALIBUS ET COMMUNITER USITATIS.	Chapter 38. On general and commonly used rules.
Regulae generales sunt multae. Una est quod ex vero numquam sequitur falsum; et ideo quandocumque antecedens est verum et consequens falsum, consequentia non valet.	There are many general rules. One thing is that falsity never follows from truth; and therefore whenever the antecedent is true and the consequent falsity, the conclusion is invalid.
Et haec est ratio sufficiens ad probandum consequentiam non valere. Sciendum est quod antecedens est totum quod praecedit conclusionem; et ideo aliquando antecedens est tantum una propositio et aliquando continet plures propositiones, sicut patet in syllogismo. Et tunc, ƿ quamvis una illarum propositionum sit vera, conclusio poterit esse falsa; sed si quaelibet illarum fuerit vera, non poterit conclusio esse falsa si sequatur ex eis. Alia regula est quod ex falsis potest sequi verum. Et ideo ista consequentia non valet `antecedens est falsum, igitur consequens est falsum'; sed ista consequentia est bona `consequens est falsum, igitur et antecedens', ita quod si consequens sit falsum, oportet quod totum antecedens sit falsum vel quod aliqua propositio quae est pars antecedentis sit falsa.	And this is a sufficient reason to prove that the conclusion is not valid. It must be known that the antecedent is all that precedes the conclusion; and therefore sometimes the antecedent is only one proposition, and sometimes it contains several propositions, as is evident in the syllogism. And then, although one of those propositions is true, the conclusion may be false; but if all of them be true, the conclusion cannot be false if it follows from them. Another rule is that truth can follow from falsities. And therefore this conclusion does not hold: `the antecedent is false, therefore the consequent is false'; but this conclusion is good: "the consequent is false, and therefore also the antecedent," so that if the consequent is false, the whole of the antecedent must be false, or that some proposition which is a part of the antecedent must be false.
Sed non oportet quod quaelibet propositio quae est pars antecedentis sit falsa, quia aliquando ex una propositione vera et alia falsa sequitur conclusio falsa, sicut patet hic `omnis homo est animal; lapis est homo; igitur lapis est animal'.	But it is not necessary that every proposition which is a part of the antecedent be false, because sometimes a false conclusion follows from one proposition being true and another being false, as is clear here: 'every man is an animal'; man is a stone; therefore a stone is an animal.
Alia regula est: si aliqua consequentia sit bona, ex opposito consequentis sequitur oppositum antecedentis. Notandum quod quando antecedens est una propositio, semper si sit consequentia bona, ex opposito consequentis sequitur oppositum totius antecedentis.	Another rule is: if any consequence is good, the opposite of the antecedent follows from the opposite of the consequence. It should be noted that when the antecedent is a single proposition, always if the consequent is good, the opposite of the consequent follows from the opposite of the entire antecedent.
Sed quando antecedens continet plures propositiones, tunc non oportet quod ex opposito consequentis sequatur oppositum cuiuslibet propositionis quae est pars antecedentis, sed oportet quod ex opposito consequentis cum una propositionum sequatur oppositum alterius propositionis.	But when the antecedent contains several propositions, then it is not necessary that from the opposite of the consequent follow the opposite of any proposition which is a part of the antecedent, but it is necessary that from the opposite of the consequent with one of the propositions the opposite of the other proposition follows.
Sicut bene sequitur `omnis homo est albus; Sortes est homo; igitur Sortes est albus', et tamen non sequitur `Sortes non est albus, igitur Sortes non est homo', sed bene sequitur `omnis homo est albus; Sortes non est albus; igitur Sortes non est homo'.	As it well follows, ``every man is white; Socrates is a man; therefore Socrates is white', and yet it does not follow that `Socrates is not white, therefore Socrates is not a man, but it follows well that 'every man is white'; Socrates is not white; Therefore Socrates is not a man.
Et ita ex opposito conclusionis et maiore sequitur oppositum minoris et non ex solo opposito conclusionis. Similiter bene sequitur `omnis homo est animal; asinus est homo; igitur asinus est animal', et tamen ex solo opposito conclusionis non sequitur oppositum maioris, nam non sequitur `nullus asinus est animal, igitur non omnis homo est animal'.	And so from the opposite of the conclusion and the greater follows the opposite of the lesser and not from only the opposite of the conclusion. Similarly, it follows well that every man is an animal; a donkey is a man; therefore a donkey is an animal', and yet from the only opposite conclusion the opposite of the greater one does not follow, for it does not follow that 'no ass is an animal, therefore not every man is an animal'.
Sed ex opposito conclusionis et minore sequitur oppositum maioris; nam bene sequitur ƿ 'nullus asinus est animal; asinus est homo; igitur non omnis homo est animal'. Alia regula est: quidquid sequitur ad consequens, sequitur ad antecedens; sicut si sequitur `omne animal currit, igitur omnis homo currit', quidquid sequitur ad istam `omnis homo currit' sequitur ad istam `omne animal currit'.	But from the opposite conclusion and the minor follows the opposite of the major; for it follows well that 'no donkey is an animal; a donkey is a man; therefore not every man is an animal. Another rule is: whatever follows for the consequent follows for the antecedent; just as if it follows that `every animal runs, then every man runs', whatever follows from this `every man runs' follows from this `every animal runs'.
Ex ista regula sequitur alia, scilicet: quidquid antecedit ad antecedens, antecedit ad consequens; quia aliter aliquid sequeretur ad consequens quod non sequeretur ad antecedens.	Another rule follows from this rule, namely: whatever precedes the antecedent, precedes the consequent; because otherwise something would follow to the consequence which would not follow to the antecedent.
Sed istae regulae falsae sunt: quidquid sequitur ad antecedens, sequitur ad consequens; nam sequitur `omne animal currit, igitur omnis homo currit' et tamen non sequitur `omnis homo currit, igitur omnis asinus currit'.	But these rules are false: whatever follows from the antecedent follows from the consequent; for it follows that `every animal runs, therefore every man runs' and yet it does not follow that `every man runs, therefore every donkey runs'.
Similiter ista regula est falsa `quidquid antecedit ad consequens, antecedit ad antecedens', propter idem.	Similarly, this rule is false, `whatever precedes the consequent, precedes the antecedent', for the same reason.
Ex istis sequuntur aliae regulae. Una est: quidquid stat cum antecedente, stat cum consequente; sicut quidquid stat cum ista `omne animal currit' stat cum ista `omnis homo currit'.	Other rules follow from these. It is one thing: whatever stands with the antecedent stands with the consequent; just as whatever stands with the words `every animal runs' stands with the words `every man runs'.
Sed non quidquid stat cum consequente stat cum antecedente; nam cum isto consequente `omnis homo currit' stat ista `aliquis asinus non currit', sed tamen non stat cum ista `omne animal currit'.	But whatever stands with the consequent does not stand with the antecedent; for with this consequence, `every man runs,' the statement `some donkey does not run,' stands, but it does not stand with the statement, `every animal runs.'
Et hoc quando antecedens non sequitur ad consequens nec consequentia simplici nec consequentia ut nunc. Alia regula est: quidquid repugnat consequenti, repugnat antecedenti; sicut quidquid repugnat isti `omnis homo currit' repugnat etiam isti `omne animal currit'.	And this when the antecedent does not follow to the consequent, neither a simple consequence nor a consequence as now. Another rule is: whatever is contrary to the consequent is contrary to the antecedent; just as whatever contradicts this `every man runs' also contradicts this `every animal runs'.
Sed non e converso, quia aliquid repugnat antecedenti quod non repugnat consequenti; quia ista repugnant `tanƿtum homo currit' et `aliud ab homine currit', sed ista non repugnant `homo currit' et `aliud ab homine currit'.	But not the other way around, because something is inconsistent with an antecedent that is not inconsistent with a consequent; for some things are inconsistent with `a man runs' and `another thing runs from a man', but others are not inconsistent with a `a man runs' and `another thing runs from a man'.
Et ideo tales consequentiae sunt bonae: oppositum consequentis stat cum antecedente, igitur consequentia non valet; oppositum consequentis non stat cum antecedente, ergo consequentia est bona.	And therefore such inferences are good: the opposite of the inference stands with the antecedent, therefore the inference is not valid; the opposite of the consequent does not stand with the antecedent, therefore the consequence is good.
Sed sciendum quod consequentia poterit esse bona ut nunc, quamvis oppositum consequentis possit stare cum antecedente; sed si oppositum consequentis stet vel possit stare cum antecedente, non poterit esse consequentia simplex.	But it must be known that the consequence may be good as now, although the opposite of the consequence may stand with the antecedent; but if the opposite of the consequent stands or can stand with the antecedent, it cannot be a simple consequence.
Alia regula est quod ex necessario non sequitur contingens.	Another rule is that the contingent does not necessarily follow.
Alia regula est quod ex possibili non sequitur impossibile. Istae duae regulae intelligendae sunt de consequentia simplici, quia ex necessario non sequitur contingens consequentia simplici, nec ex possibili impossibile, tamen consequentia ut nunc bene poterit sequi; sicut bene sequitur `omne ens est, igitur omnis homo est', et tamen antecedens est necessarium et consequens contingens. Similiter bene sequitur `omne coloratum est homo, igitur omnis asinus est homo', et tamen antecedens est possibile et consequens impossibile, et consequentia solum est bona ut nunc. Et notandum est etiam quod quamvis ex possibili non sequatur impossibile consequentia simplici, tamen aliquando propter positionem possibilis concedendum est impossibile et negandum est necessarium; sed hoc numquam est faciendum nisi in arte obligatoria et durante tempore obligationis, de qua arte aliquid inferius dicetur.	Another rule is that the impossible does not follow from the possible. These two rules are to be understood of simple consequence, because a contingent simple consequence does not follow from necessity, nor an impossible from possible, yet the consequence may well follow now; as it follows well that 'every being is, therefore every man is', and yet the antecedent is necessary and the consequent contingent. Similarly, it follows well that 'every colored thing is a man, therefore every donkey is a man', and yet the antecedent is possible and the consequent impossible, and the consequence is only good as now. And it is also to be noted that although the impossible does not follow from the simple consequence of the possible, yet sometimes because of the position of the possible the impossible must be granted and the necessary denied; but this must never be done except in an obligatory art and during the period of the obligation, about which art something will be said below.
Aliae regulae dantur, quod `ex impossibili sequitur quodlibet' et ƿ quod `necessarium sequitur ad quodlibet'; et ideo sequitur `tu es asinus, igitur tu es Deus', et sequitur `tu es albus, igitur Deus est trinus et unus'.	Other rules are given, that `everything follows from the impossible' and that `the necessary follows from everything'; and therefore it follows that `you are an ass, therefore you are God', and it follows that `you are white, therefore God is triune and one'.
Sed tales consequentiae non sunt formales, et ideo istae regulae non sunt multum usitatae.	But such consequences are not formal, and therefore these rules are not much used.