Authors/Thomas Aquinas/posteriorum/L2/Lect19

Lecture 19 Whether upon unity of cause follows unity of effect, and vice versa. How cause and effect follow upon one another

Latin	English
	Lecture 19 (99a1-b18) WHETHER UPON UNITY OF CAUSE FOLLOWS UNITY OF EFFECT, AND VICE VERSA HOW CAUSE AND EFFECT FOLLOW UPON ONE ANOTHER
lib. 2 l. 19 n. 1 Postquam philosophus determinavit quaestionem motam, utrum ad existentiam effectus sequatur existentia causae, et e converso; hic inquirit utrum ad unitatem causae sequatur unitas effectus et e converso. Et circa hoc duo facit: primo, ostendit quomodo ad unitatem effectus sequatur unitas causae; secundo, ex hoc manifestat consecutionem causae et effectus; ibi: habet autem sic consequi et cetera. Circa primum tria facit: primo, proponit quaestionem; quae est, utrum contingat quod eiusdem effectus non sit eadem causa in omnibus, sed alia et alia, vel non. Videbatur enim in solutione praemissae quaestionis supponi quod contingat unius effectus in diversis rebus esse diversas causas.	Having settled the question he raised, namely, whether upon the existence of the effect the existence of the cause follows, and conversely; the Philosopher now inquires whether unity of cause follows upon unity of effect, and conversely. Concerning this he does two things. First, he shows how one cause is inferred from one effect. Secondly, from this he shows the sequential connection of cause and effect (99a17). In regard to the first he does three things. First (99a1) he proposes the question, which is this: Does it occur that of the same effect there is not the same cause in all cases but different ones, or does this not occur? For it seemed to be supposed in solving the previous question that in various cases there can be various causes of one effect.
lib. 2 l. 19 n. 2 Secundo, ibi: aut si quidem per se etc., solvit quaestionem distinguendo. Contingit enim aliquid assignari pro causa alicuius effectus tripliciter: uno modo, accipiendo causam per se, et sic demonstrative concludendo effectum; alio modo, accipiendo aliquod signum; tertio modo, accipiendo aliquod accidens. Si ergo accipiatur pro causa id quod per se est medium demonstrationis, non potest esse nisi una causa unius effectus in omnibus. Et hoc probat quia medium per se in demonstrationibus est ratio ultimi, idest definitio maioris extremitatis. Quae tamen si demonstrari indigeat de subiecto, demonstrabitur per definitionem subiecti, ut supra habitum est. Manifestum est autem quod unius una est definitio. Unde oportet quod unius effectus non accipiatur nisi una causa, quae est medium demonstrationis.	Secondly (99a2), he solves the question by distinguishing. For it occurs that something is assigned as the cause of some effect in three ways: in one way, by taking the per se cause and then concluding the effect demonstratively; in another way, by taking a sign; in a third way, by taking an accident. Therefore, if one takes as cause that which is per se the middle of demonstration, there can be but one cause of one effect in all cases. And he proves this on the ground that a per se middle in demonstrations is a formality of the ultimate, i.e., the definition of the major extreme, which, if it needs to be demonstrated of the subject, will be demonstrated by the definition of the subject, as we have established above. Now it is obvious that of one thing there is one definition. Hence it is necessary that of one effect there is no cause but the one which is the middle of demonstration.
Si vero non accipiatur quasi causa inferens, id quod est per se medium demonstrationis, sed accipiatur pro medio aliquod signum vel aliquod accidens, tunc contingit unius effectus accipi quasi plures causas in diversis, sicut patet in exemplo superius posito. Per se enim causa quod aliquid sit vituperabile, est esse praeter rationem rectam. Sed quod aliquid sit superabundans vel deficiens, est signum eius quod est praeter rationem rectam.	However, if one does not take as the inferring cause that which is per se the middle of demonstration, but some sign or accident is used as the middle, then it does happen that of one effect several causes, as it were, are taken in diverse things, as is clear in the example given earlier. For the per se cause why something is blameworthy is that it is not according to reason. But to be excessive or defective is a sign of that which is not according to reason.
lib. 2 l. 19 n. 3 Tertio, ibi: est autem et causam et etc., manifestat positam solutionem, ostendens membra divisionis positae esse possibilia. Et dicit quod contingit et id quod est causa et id cuius est causa considerare secundum accidens; sicut musicus per accidens est causa domus, cuius per se est causa aedificator, qui tamen est causa receptaculi latronum per accidens, si contingat hoc in domo fieri: quinimo etiam ipsa problemata videntur esse per accidens. Si vero non accipiantur per accidens causa et causatum, oportet quod medium quod accipitur pro causa, similiter se habeat cum effectu, cuius demonstratio quaeritur.	Thirdly (99a4), he elucidates his solution by showing that the members of the division he cited are possible. And he says that it is possible to consider both that which is the cause and that of which it is the cause, per accidens: thus a musician is per accidens the cause of a house whose per se cause is a builder, who in turn is per accidens the cause of its being a haven for thieves, if this happens to occur in the house. Indeed, these problems even seem to be per accidens. But if cause and caused are not taken per accidens, it is required that the middle taken as cause be of the same order as the effect whose demonstration is sought.
Utpote si aliqua sint aequivoca, et medium commune quod accipitur, erit aequivocum. Si autem non sint aequivoca, sed conveniant quasi in genere, et medium erit commune secundum genus; sicut vicissim analogum, idest commutatim proportionari, univoce in multis invenitur, puta in numeris et in lineis, in quibus habet quodammodo aliam causam, et quodammodo eamdem. Aliam quidem secundum speciem, in quantum scilicet alii sunt numeri et aliae lineae: sed est genere eadem, in quantum scilicet tam lineae quam numeri conveniunt in hoc quod habent tale augmentum, ex quo in eis commutata proportio demonstratur.	Hence if certain things are equivocal, then the common middle which is taken will also be equivocal; if they are not equivocal but agree as it were in genus, then the middle too will be common according to genus. Thus the fact that proportionals alternate, i.e., are commutatively proportional, is found univocally in many things, say in numbers and in lines, in which they have a cause which is in one sense different and in one sense the same: different, indeed, according to species, inasmuch as a line is one thing and a number another thing; but the same according to genus, inasmuch as lines as well as numbers agree in having such increments from which commutative proportion is demonstrated of them.
Aliud autem exemplum subiungit in aequivocis; et dicit quod eius quod est esse simile, alia causa est in coloribus et in figuris, quia aequivoce dicitur utrobique. In figuris enim nihil est aliud esse simile, quam quod latera habeant analogiam, idest quod sint ad invicem proportionalia, et quod anguli sint aequales. Sed in coloribus esse simile est quod faciant eamdem immutationem in sensu, vel aliquid aliud huiusmodi. Tertio autem dicit de his quae conveniunt secundum analogiam, quod in his etiam oportet esse medium unum secundum analogiam; sicut supra dictum est quod tam iris quam echo est quaedam repercussio.	The other examples he gives concern equivocal things. He says that the cause of being similar is one thing in colors and another in figures, because similarity is predicated equivocally of the two. For in figures, to be similar consists in nothing more than that the sides have anology, i.e., that the sides are proportional and the angles equal. But in colors, similarity consists in the fact that they cause the same alteration in the sense, or something else of this sort. Thirdly, however, he says concerning things which agree according to analogy that in their case it is also required that the middle be one according to analogy, as when it was stated above that both a rainbow and an echo are reverberations.
lib. 2 l. 19 n. 4 Deinde cum dicit: habet autem sic consequi causam etc., ostendit secundum praemissa qualiter sibi invicem causae consequantur. Et circa hoc tria facit: primo, ostendit qualis sit consecutio causae et effectus; secundo, ordinat huiusmodi consequentiam in figura syllogistica; ibi: in figuris autem etc.; tertio, movet quamdam dubitationem ex praemissis; ibi: si autem in atomum et cetera.	Then (99a17) he shows how in the light of the foregoing, causes follow one upon the other. Concerning this he does three things. First, he shows what sort of sequential connection there is between cause and effect. Secondly, he orders this connection in a syllogistic figure (99a30). Thirdly, he raises a doubt from the foregoing (99b7).
Dicit ergo primo quod talis modus consequentiae invenitur inter causam et causatum et subiectum cui inest illud causatum, quod si aliquis accipiat secundum unum aliquid particulare id cuius causa quaeritur, erit in plus quam causa vel subiectum; sicut habere angulos extrinsecos aequales quatuor rectis convenit triangulo eadem ratione, quia tres anguli eius extrinseci simul cum tribus intrinsecis sunt aequales sex rectis. Cum igitur tres intrinseci sint aequales duobus rectis, sequitur quod tres extrinseci sint aequales quatuor rectis. Etiam quadrangulus habet quatuor angulos aequales quatuor rectis, sed alia ratione. Anguli enim eius intrinseci et extrinseci sunt aequales octo rectis; sed anguli intrinseci quadranguli sunt aequales quatuor rectis; ergo anguli extrinseci sunt aequales quatuor rectis. Sic igitur habere angulos exteriores aequales quatuor rectis, est in plus quam triangulus aut quadrangulus: sed si simul accipiantur, aequaliter se habebunt. Quaecunque enim figurae communicant in hoc quod habeant angulos exteriores aequales quatuor rectis, oportet quod similiter communicent in medio, quod est causa aequalitatis ad quatuor angulos rectos. Et hoc probat sicut et prius, per hoc quod medium est definitio maioris extremitatis. Et inde est quod omnes scientiae fiunt per definitionem.	He says therefore first (99a17) that the type of connection found between cause and caused and the subject in which that caused inheres is such that if one were to take in a particular case that of which the cause is sought, it will be in more than the cause or subject. Thus, to have its exterior angles equal to four right angles belongs to every triangle for a single reason, namely, because its three exterior angles added to its three interior angles are equal to six right angles. Therefore, since the three interior angles are equal to two right angles, it follows that the three exterior angles are equal to four right angles. However, a rhombus also has four exterior angles equal to four right angles, but for another reason. For its exterior angles plus its interior angles equal eight right angles, but the four interior angles of a rhombus are equal to four right angles; therefore, the four exterior angles are equal to four right angles. Therefore, to have its exterior angles equal to four right angles extends to more things than either triangle or rhombus does; but if the latter are taken together, they are equal to the former. For all figures, which agree in having their exterior angles equal to four right angles must similarly agree as to their middle, which is the cause of being equal to four right angles. And he proves this, as in the previous case, on the ground that the middle is the definition of the major extreme. And this is why all sciences come to be in virtue of a definition.
Probat autem hoc per exemplum in rebus naturalibus. Hoc enim quod est folio fluere, consequitur ad vitem et excedit ipsam, quia est in pluribus; consequitur etiam ad ficum et excedit eam: non tamen est excessivum omnium quibus convenit, sed est eorum sicut aequalium. Si ergo aliquis velit accipere id quod est primum medium respectu omnium, erit haec definitio eius quod est folio fluere; quae quidem definitio erit primum medium ad alia, eo quod omnia talia sunt. Et iterum huius accipietur aliquod aliud medium, puta quod succus densatur per desiccationem, vel aliquod aliud huiusmodi. Unde si quaeratur quid est folio fluere, dicemus quod nihil aliud est quam condensari succum seminis in contactu, scilicet folii ad ramum.	He proves this also with an example from natural things. For the fact that its leaves fall follows on being a vine, but it extends to more, because it is true of several other things; it also follows upon being a fig tree, and extends to more. But it does not extend to more than the sum total of things in which it is found, but it is equal to their sum. Therefore, if someone desires to discover what is the first middle in relation to all, it will be the definition of the fact that the leaves fall: and this definition will be the first middle in respect to the others, since all the others are such. And again, some other middle will be discovered for this, say that the sap hardens by drying, or something of that sort. Hence, if it be asked what it is to have leaves fall off, we will say that it is nothing more than “the seminal sap hardening at a point of contact,” i.e., where the leaf meets a branch.
lib. 2 l. 19 n. 5 Deinde cum dicit: in figuris autem sic assignabit etc. ordinat modum praedictae consecutionis in figura syllogistica; et dicit quod si quaeratur consecutio causae et causati, sic poterit assignari secundum figuras syllogismorum. Sit enim a in omni b; b autem in unoquoque eorum quae sunt d, sed in plus quam d. Sic igitur b universaliter erit in his quae continentur sub d, secundum quod universaliter dicitur inesse quod non convertitur. Sed et primum universale est, cui unumquodque quidem contentorum sub eo non convertitur; omnia autem simul accepta convertuntur cum primo universali, et excedunt quodlibet eorum quae sub eo continentur. Sic igitur quod a sit in ipsis quae continentur sub d, causa est b. Oportet ergo quod a extendatur in plus quam b. Si autem non, sed se haberet ex aequo, quare magis b esset causa in inferendo quod a sit in d, quam e converso? Potest enim ex utroque convertibilium concludi aliud.	Then (99a30) he arranges the mode of the aforesaid connection in syllogistic form, saying that if the sequence of cause and caused be sought, it can, be assigned in the following way according to the figures of syllogisms. Thus let A be in every B, and B in all things that are D, but in things additional to D. Then B will inhere universally in the things contained under D, inasmuch as that is said to inhere universally which is not converted. But a primary universal is one such that each of the inferiors contained under it is not converted with it, but all of them taken together are converted with the first universal and exceed each of those which are contained under it. Thus, therefore, the cause of the fact that A inheres in the things contained under D is B. Therefore, it is required that A extend to more things than B does. If this were not so but they were equal, then why should B be the cause of inferring that A is in D, any more than A be the cause of inferring that B is in D? For either of two convertible things can be concluded from the other.
Ponatur igitur ulterius quod a praedicetur de omnibus in quibus est e, sed non convertitur. Oportet ergo dicere quod illa omnia quae continentur sub e, sint aliquid unum diversum ab eo quod est b. Si enim non esset aliud e quam b, quomodo esset verum dicere quod a inesset omni b, et non e converso, cum a non sit nisi in e et in b? Et ita sequeretur, si e et b non essent aliud, quod a non esset in plus quam e. Supponatur ergo quod a sit in plus quam d et quam e. Quare ergo non poterit inveniri aliqua causa propter quam insit omnibus quae sunt in d? Et haec causa est b. Sed adhuc quaerendum est utrum et omnia quae continentur sub e, habeant aliquam unam causam; et sit talis causa c. Sic igitur concludit quod contingit eiusdem esse plures causas, sed non in eodem secundum speciem. Sicut eius quod est a, causa est et b et c: sed b est causa quod a insit his quae continentur sub d, c autem est causa quod a insit his quae continentur sub e. Et ponit exemplum in rebus naturalibus. Sit enim hoc quod est esse longae vitae, quasi a; quadrupedia quasi d; sed non habere choleram, scilicet superfluam, sit quasi b, quod est causa in quadrupedibus longae vitae; volatilia autem sint quasi e; siccum autem esse, vel aliquid aliud huiusmodi, quod est in eis causa longae vitae, aut aliquid aliud huiusmodi sit quasi c.	Suppose, furthermore, that A is predicated of all things in which E inheres, but is not convertible. Then it will be necessary to say that all the things contained under E form one thing, which is diverse from B. For if A were not diverse from B, how could it be true to say that A inheres in every B and not vice versa, since A is only in E and in B? And so it would follow, if E and B were not diverse, that A would not be in more than E. Therefore, suppose that A is in more things than D and than E. Then why could not a cause be found explaining why it is in all things which are in D? And this cause is B. But we must still inquire whether all the things contained under E have one cause. Let C be that cause. Thus, therefore, he concludes that a same thing turns out to have several causes, but not in the same subject according to species. Thus the cause of that which is A is both B and C; but B is the cause that A is found in the things contained under D, while C is the cause that A is found in the things contained under E. And he gives an example from natural things. Let the fact of being long-lived be taken as A; quadrupeds as D; to have no bile, i.e., in superfluity (which is the cause of long life in quadrupeds) as B; birds as E; and to be dry, or something of that sort, which is the cause of long life, or something of that sort in birds, as C.
lib. 2 l. 19 n. 6 Deinde cum dicit: si autem in atomum etc., movet quamdam dubitationem ex praemissis. Dictum est enim supra quod non statim a principio venitur in aliquod atomum, idest indivisibile, in quo inveniatur illud cuius causa quaeritur; sed statim inveniuntur multa et indivisa, in quibus illud unum invenitur, et non est unum medium, per quod de omnibus illud unum demonstretur, et causae plures sunt. Est ergo dubitatio, si illorum plurium mediorum oporteat aliquam causam accipere, utrum oporteat eam accipere ex parte universalis primi, puta ex parte ipsius a; vel ex parte singularium, idest eorum quae sunt minus communia, sicut supra accipiebantur e et d, vel quadrupedia et aves.	Then (99b7) he raises a problem occasioned by the foregoing. For it was stated above that one does not straightway from the beginning arrive at something atomic, i.e., at the indivisible, in which is found that whose cause is being sought. But straightway many and indistinct things are found in which that one thing occurs; furthermore, there is not one middle through which this one thing can be demonstrated of all, and the causes are several. The doubt therefore is this: If some cause is to be taken of these several middles, is it to be taken on the side of the primary universal, say on the side of A, or on the side of the singulars, i.e., of those which are less common, as E and D were taken above, i.e., quadrupeds and birds?
Et ad hoc respondet dicens quod oportet semper media accipere quae sunt propinquiora subiecto, in quo quaeritur causa illius communis causati; et sic oportet procedere quousque perveniatur ad id quod est immediatum communi causato. Et huius rationem assignat, quia illud quod est ex parte eius quod continetur sub aliquo communi, est ei causa quod sit sub illo communi; sicut si d est sub b, et si c sit causa d quod b insit ei. Et ex hoc sequitur ulterius quod c sit causa quod a insit d; et quod a insit c, b est causa. Ipsi autem b inest a per seipsum et immediate.	And he answers this by saying that it is always required to take the middles which are nearer the subject, in which the cause of that common caused thing is searched for: and it is necessary to proceed thus until one readies that which is immediate to the common caused thing. And he assigns a reason for this, namely, because that which is on the part of what is contained under something common is the cause of its being under this common thing; just as is the case if D is under B, and if C is the cause of D having B in it. And from this it further follows that C is the cause of A’s being in D, and that B is the cause of A’s being in C. But A is in B in virtue of itself and immediately.
lib. 2 l. 19 n. 7 Ultimo autem epilogat ea quae dicta sunt in tota doctrina analyticorum; et dicit quod manifestum est ex praemissis, tam in libro priorum quam in hoc libro posteriorum, de syllogismo et de demonstratione, quid sit et quomodo fiat utrumque; et similiter manifestum est de scientia demonstrativa, quomodo fiat in nobis. Hoc enim ad idem pertinet, quia demonstratio est syllogismus faciens scire, ut supra habitum est.	Finally (99b15), he summarizes what has been said in the entire teaching of the Analytics, saying that it is clear from all that has been stated—both in the book of the Prior and in this book of the Posterior—concerning the syllogism and concerning demonstration, both what each is and how each is formed. Furthermore, in regard to demonstrative science it is also clear how it comes to exist in us. For this pertains to the same thing, because demonstration is a syllogism causing scientific knowledge, as has been established above.