Authors/Ockham/Summa Logicae/Book III-4/Chapter 12

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CAP. 12. DE FALLACIA CONSEQUENTIS. Chapter 12. On the fallacy of the consequent.
Quia secundum Aristotelem fallacia consequentis est pars accidentis, ideo post fallaciam accidentis sequitur videre de fallacia consequentis. Thus, according to Aristotle, the fallacy of the consequent is a part of accident, therefore after the fallacy of the accident it follows to examine the fallacy of the consequent.
Et est fallacia consequentis quando creditur antecedens sequi ad consequens sicut consequens sequitur ad antecedens. Ita quod causa apparentiae istius fallaciae provenit ex similitudine consequentis ad antecedens; et causa non-exsistentiae est diversitas inter antecedens et consequens. And there is a fallacy of the consequent when it is believed that the antecedent follows the consequent as the consequent follows the antecedent. So that the cause of the appearance of this fallacy comes from the similarity of the consequent to the antecedent; and the cause of its non-existence is the diversity between the antecedent and the consequent.
Fit autem fallacia consequentis vel arguendo ex propositionibus quarum una sequitur ad aliam et non e converso; vel arguendo ex una condicionali ad aliam condicionalem in qua oppositum antecedentis primae condicionalis ponitur antecedens et oppositum consequentis primae condicionalis ponitur loco consequentis. But the fallacy of the consequent occurs either by arguing from propositions one of which follows from another and not vice versa; or by arguing from one conditional to another conditional in which the opposite of the antecedent of the first conditional is placed as the antecedent and the opposite of the consequent of the first conditional is placed in place of the consequent.
Sicut sic arguendo `si homo currit, animal currit; igitur si nullus homo currit, nullum animal currit'. As in arguing thus `if a man runs, an animal runs; therefore if no man runs, no animal runs'.
Hic enim est fallacia consequentis. Et est regula generalis pro omnibus talibus quod quando arguitur ex condicionali una ad aliam condicionalem, in qua oppositum antecedentis primae ponitur loco antecedentis et oppositum consequentis loco consequentis, est fallacia consequentis. For here is the fallacy of the consequent. And there is a general rule for all such things that when an argument is made from one conditional to another conditional, in which the opposite of the first antecedent is put in place of the antecedent and the opposite of the consequent in place of the consequent, there is a fallacy of the consequent.
Et hoc propter istam regulam: quamvis aliqua consequentia sit bona, non oportet oppositum antecedentis inferre oppositum consequentis, quamvis aliquando gratia terminorum ex opposito antecedentis sequatur oppositum consequentis. And this is because of this rule: although a consequence is good, one must not infer the opposite of the antecedent from the opposite of the consequent, although sometimes, by virtue of the terms, the opposite of the consequent follows from the opposite of the antecedent.
Et ideo de isto non oportet plus loqui, quia evidenter potest sciri quando iste modus accidit et quando non, scita ista regula data nunc, et scito quando est alius modus istius fallaciae. Unde sciendum est quod quandoque committitur fallacia consequentis arguendo enthymematice et quandoque arguendo ex pluribus propositionibus. And therefore there is no need to speak more about this, because it can be clearly known when this mode occurs and when it does not, knowing this rule given now, and knowing when there is another mode of this fallacy. Hence it should be known that sometimes the fallacy of the consequent is committed by arguing enthymematically and sometimes by arguing from several propositions.
Si arguatur ex pluribus propositionibus, ad hoc quod sit consequens requiritur quod consequens inferat quamlibet propositionem positam in antecedente, et non e converso. If it is argued from several propositions, for it to be consequent it is required that the consequent infer any proposition placed in the antecedent, and not vice versa.
Et si arguatur in figura, semper simul cum hoc erit fallacia accidentis. Et universaliter quando est fallacia consequentis etiam in enthymemate, et illa consequentia reducitur in figuram debitam, si remaneat fallacia consequentis in illo discursu composito ex propositionibus dispositis in figura, erit non solum fallacia consequentis, sed etiam erit fallacia accidentis. And if it is argued in a figure, there will always be a fallacy of accident along with this. And universally, when there is a fallacy of the consequent even in an enthymeme, and that consequence is reduced to the proper figure, if the fallacy of the consequent remains in that discourse composed of propositions arranged in the figure, there will be not only a fallacy of the consequent, but there will also be a fallacy of accident.
Et pro tanto dicit Philosophus quod consequens est pars accidentis, quia ubicumque est dispositio propositionum in figura, si sit ibi fallacia consequentis, erit etiam ibi fallacia accidentis, sed non e converso. And for this reason the Philosopher says that the consequent is a part of the accident, because wherever there is an arrangement of propositions in a figure, if there is a fallacy of the consequent there, there will also be a fallacy of the accident there, but not vice versa.
Unde hic est fallacia consequentis `omnis homo est animal; omnis asinus est animal; ergo omnis asinus est homo', quia utraque praemissa sequitur ex conclusione et non e converso; et est etiam hic fallacia accidentis, sicut patet per praedicta. Hence here is a fallacy of the consequent `every man is an animal; every donkey is an animal; therefore every donkey is a man', because both premises follow from the conclusion and not vice versa; and here too there is a fallacy of accident, as is clear from what has been said.
Sed hic `omnis homo est albus; omnis homo est visus; ergo omne visum est album' est fallacia accidentis, sed non est hic fallacia consequentis, quia conclusio nullam praemissam infert. But this, `every man is white; every man is a seen thing; therefore every seen thing is white', is a fallacy of accident, but it is not here a fallacy of the consequent, because the conclusion does not imply any premise.
Et ideo falsum est quod aliqui dicunt quod semper arguendo ex omnibus affirmativis in secunda figura est facere fallaciam consequentis. Videndum est ergo de fallacia consequentis arguendo enthymematice, quo viso scietur faciliter quando generaliter est fallacia consequentis, sive arguatur ex pluribus praemissis sive non. And therefore it is false what some say, that by always arguing from all the affirmatives in the second figure, one is creating a fallacy of the consequent. Therefore, we must see about the fallacy of the consequent by arguing enthymematically, by which it will be easily known when there is a fallacy of the consequent in general, whether it is argued from several premises or not.
Unde sciendum quod ad assignandum fallaciam consequentis non sufficit dicere quod sequitur e converso et non sic. Quamvis enim ista sit generalis solutio, tamen praeter istam solutionem generalem oportet dare aliam regulam specialem quare sequitur e converso et non sic. Hence it should be known that to assign the fallacy of the consequent it is not enough to say that it follows conversely and not thus. For although this is a general solution, nevertheless, in addition to this general solution it is necessary to give another special rule why it follows from the converse and not so.
Et hoc est in assignando duas regulas speciales, per quarum unam declaratur quod sequitur e converso et per aliam quod non sequitur sic. Et ita generaliter in assignatione fallaciae consequentis oportet duas regulas speciales assignare et pro diversis sophismatibus oportet diversis regulis uti, de quibus aliquae gratia exempli subicientur. And this is in assigning two special rules, by one of which it is declared that it follows conversely and by the other that it does not follow thus. And so generally in assigning the fallacy of the consequent it is necessary to assign two special rules and for different sophisms it is necessary to use different rules, of which some examples will be given for the sake of example.
Unde sciendum quod quando arguitur ab inferiori distributo ad superius distributum est fallacia consequentis. Hence it should be known that when an argument is made from a lower distribution to a higher distribution, it is a fallacy of the consequent.
Sicut hic est fallacia consequentis `omnis homo currit, igitur omne animal currit'. Tenet enim e converso per istam regulam `a superiori distributo ad inferius distributum est bona consequentia'; non tenet autem sic, quia ab inferiori ad superius cum distributione non valet consequentia. Just as here is a fallacy of the consequent: `every man runs, therefore every animal runs'. For conversely, by this rule `from a higher distributed to a lower distributed is a good consequence' holds; but it does not hold in this way, because the consequence from a lower to a higher is not valid with distribution.
Similiter quando arguitur a termino stante confuse tantum ad terminum stantem determinate, nulla variatione facta circa alios terminos, est fallacia consequentis. Similarly, when an argument is made from a term that stands confusedly only to a term that stands determinately, with no variation made regarding other terms, it is a fallacy of the consequent.
Sicut hic est fallacia consequentis `omnis homo est animal, igitur animal est omnis homo'. Tenet enim e converso, per istam regulam `a termino stante determinate ad terminum stantem confuse tantum, nulla variatione facta circa alios terminos, est bona consequentia', eo quod contingit ascendere ad terminum stantem confuse tantum. Just as here is a fallacy of the consequent: `every man is an animal, therefore an animal is every man'. For it holds conversely, by this rule `from a term standing determinately to a term standing only confusedly, with no variation made about other terms, is a good consequence', because it is possible to ascend to a term standing only confusedly.
Non tenet autem sic, propter istam regulam quae nunc dicta est, scilicet quod `a termino stante confuse tantum ad terminum stantem determinate non valet consequentia'. Unde per istum modum peccant omnia talia sophismata: omni parte istius continui est aliqua pars eius prius terminata, ergo aliqua pars istius continui est prius terminata omni parte istius continui; inter omne instans futurum et hoc instans est aliquod instans medium, ergo aliquod instans est medium inter omne instans futurum et hoc instans; omni quantitate potest fieri aliqua quantitas maior, igitur potest fieri aliqua quantitas maior omni quantitate; post omnem diem potest esse aliqua dies, ergo aliqua dies potest esse post omnem diem; omni parte continui potest dari aliqua pars minor, ergo aliqua pars minor omni parte continui potest dari. But it does not hold thus, because of that rule which has just been stated, namely that `from a terminus standing only confusedly to a terminus standing determinately the consequence is not valid'. Hence in this way all such sophisms err: in every part of that continuum there is some part of it previously terminated, therefore some part of that continuum is previously terminated in every part of that continuum; between every future instant and this instant there is some intermediate instant, therefore some instant is intermediate between every future instant and this instant; some quantity can be made greater than every quantity, therefore some quantity can be made greater than every quantity; after every day there can be some day, therefore some day can be after every day; in every part of the continuum there can be some smaller part, therefore some smaller part can be made in every part of the continuum.
In omnibus enim istis et consimilibus praedicatum in antecedente supponit confuse tantum, propter hoc quod sequitur signum mediate, et in conclusione supponit determinate, quia praecedit signum, ideo est fallacia consequentis. For in all these and similar cases the predicate in the antecedent supposits only confusedly, because the sign follows mediately, and in the conclusion it supposits determinately, because the sign precedes, therefore it is a fallacy of the consequent.
<Similiter est hic>: utrumque istorum potest esse verum, <demonstratis duobus contradictoriis dubitabilibus>, ergo aliquod verum potest esse utrumque istorum. Item, arguendo a termino stante determinate vel confuse tantum ad terminum stantem confuse et distributive, est fallacia consequentis. <It is similar here>: both of these can be true, <having demonstrated two doubtful contradictions>, therefore something true can be both of these. Likewise, by arguing from a term that stands determinately or only confusedly to a term that stands confusedly and distributively, there is a fallacy of the consequent.
Sicut hic: tu ignoras aliquam propositionem, ergo tu nescis aliquam propositionem; tu dubitas aliquid, igitur tu nescis aliquid; Sortes videt non-hominem, ergo Sortes non videt hominem. As here: you are ignorant of some proposition, therefore you do not know some proposition; you doubt something, therefore you do not know something; Socrates sees a non-man, therefore Socrates does not see a man.
Item, quando obliquus et rectus sequuntur signum universale affirmativum, primo ponendo rectum post signum et obliquum, et post praeponendo rectum signo et obliquo, est facere fallaciam consequentis. Likewise, when the oblique and the direct follow a universal affirmative sign, by first placing the direct after the sign and the oblique, and then by placing the direct before the sign and the oblique, one is creating a fallacy of the consequent.
Sicut sic arguendo `omnem hominem videns est asinus, ergo videns omnem hominem est asinus'; quia ponatur quod quilibet asinus videat aliquem hominem et nullus asinus videat omnem hominem, tunc est antecedens verum et consequens falsum. For example, by arguing that `everything seeing a man is an ass, therefore something seeing every man is an ass'; because it is assumed that every ass sees some man and no ass sees every man, then the antecedent is true and the consequent false.
Item, quando alicuius universalis quaelibet singularis per se sumpta est vera, tamen simul sumpta sunt incompossibilia, et tamen quaelibet est compossibilis alteri, tunc arguendo ab universali de possibili, aequivalenti sensui compositionis, ad propositionem de possibili in qua subiectum cum eodem signo ponitur a parte praedicati, est fallacia consequentis. Likewise, when any singular of some universal taken by itself is true, yet taken together they are incomposable, and yet each is composable with the other, then arguing from the universal de possibili, equivalent to the sense of composition, to a proposition de possibili in which the subject is placed with the same sign on the part of the predicate, is a fallacy of the consequent.
Sicut sic arguendo `secundum omne signum potest continuum dividi, igitur continuum potest dividi secundum omne signum'. Nec sequitur `continuum potest dividi secundum hoc signum et continuum potest dividi secundum illud signum, et sic de singulis, ergo continuum potest dividi secundum omne signum'. Just as by arguing thus `according to every sign a continuum can be divided, therefore a continuum can be divided according to every sign.' Nor does it follow `a continuum can be divided according to this sign and a continuum can be divided according to that sign, and so on for each, therefore a continuum can be divided according to every sign.'
Tamen frequenter in auctoribus una talium propositionum ponitur loco alterius, quamvis de virtute sermonis non aequivaleant. Propter quod in talibus est fallacia consequentis, secundum principia Aristotelis, `omni forma potest haec materia privari, igitur haec materia potest privari omni forma'. Yet frequently in authors one of such propositions is put in place of the other, although they are not equivalent in reality. Because of this, in such propositions there is a fallacy of the consequence, according to Aristotle's principles, `of every form this matter can be deprived, therefore this matter can be deprived of every form'.
Per istam enim `omni forma potest haec materia privari' non denotatur nisi quod quaelibet talis sit possibilis `hac forma privatur haec materia', quacumque forma demonstrata. For by this `of every form this matter can be deprived' is denoted nothing but that any such `this matter is deprived of this form' is possible, whatever form is demonstrated.
Et manifestum est, secundum principia Aristotelis, quod quaelibet talis est vera. Sed per istam `haec materia potest privari omni forma' denotatur quod haec sit possibilis `haec materia est privata omni forma'. And it is clear, according to Aristotle's principles, that any such thing is true. But by this `this matter can be deprived of every form' is denoted that this is possible `this matter is deprived of all form'.
Sed haec est impossibilis, secundum principia Aristotelis. Similiter hic est fallacia consequentis `in omni instanti futuro potest iste peccare, --- demonstrato aliquo qui nunc est sub actu meritorio ---, igitur iste potest peccare in omni instanti futuro'. But this is impossible, according to Aristotle's principles. Similarly, here is a fallacy of the consequent `in every future instant this person can sin, --- pointing to someone who is now doing a meritorious act ---, therefore this person can sin in every future instant'.
Nam antecedens est verum et consequens falsum, eo quod non est dare ultimum rei permanentis in esse, et per consequens si iste actus meritorius est, erit post hoc instans. Similiter hic est fallacia consequentis `ante omne instans futurum potest Sortes non esse, ergo Sortes potest non esse ante omne instans futurum'. For the antecedent is true and the consequent false, because it is not possible to give the ultimate of a thing that remains in being, and consequently if this act is meritorious, there will be an instant after this. Similarly, here is a fallacy of the consequent `before every future instant Socrates cannot be, therefore Socrates cannot be before every future instant'.
Item, quando aliqua propositio modalis non potest converti transponendo praecise terminos sequentes et praecedentes verbum vel verba, arguendo a tali modali indefinita vel universali ad conversam singularem vel ei aequivalentem est fallacia consequentis quantum est ex forma arguendi, quamvis in aliquibus terminis teneat. Likewise, when some modal proposition cannot be converted by precisely transposing the terms following and preceding the word or words, arguing from such an indefinite or universal modal to a converted singular or equivalent is a fallacy of the consequent as far as it is from the form of the argument, although it holds for some terms.
Propter quod in talibus est fallacia consequentis `actum meritorium potest Deus facere se solo, ergo Deus se solo potest facere actum meritorium'. Verumtamen sciendum est quod in omnibus praedictis potest assignari fallacia figurae dictionis. Because of this, in such things there is a fallacy of the consequent: `God can perform a meritorious act by himself alone, therefore God alone, by himself can perform a meritorious act.' However, it should be known that in all the above, a fallacy of figure of speech can be assigned.
Multae aliae regulae possent dari deservientes isti fallaciae. Sed sciendum est quod ad sciendum generaliter quando est fallacia consequentis et quando non, oportet scire omnes regulas, datas prius, deservientes consequentiis, et universaliter omnes quae possunt deservire cuicumque enthymemati. Et ideo nisi sciantur omnes regulae consequentiarum non potest universaliter sciri quando est ista fallacia et quando non accidit huiusmodi fallacia. Many other rules could be given that serve this fallacy. But it should be known that in order to know generally when there is a fallacy of the consequent and when not, it is necessary to know all the rules given previously that serve consequences, and universally all those that can serve any enthymeme. And therefore unless all the rules of consequences are known, it cannot be known universally when this fallacy exists and when this kind of fallacy does not occur.

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