St. Thomas Aquinas, Latin Averroism and the Autonomy of Philosophy
Influenced by post-Enlightenment mentality, one may easily fall prey to the following, as I shall argue deceptive, piece of reasoning.
Any methodological doctrine that imposes theological dogma upon philosophical inquiry delimits the autonomy of philosophical inquiry. Therefore, ex opposito, any methodological doctrine that separates theological dogma from philosophical inquiry increases the autonomy of philosophical inquiry. But the Latin Averroist methodological doctrine of veritas duplex (rather improperly, but not entirely unreasonably called so) separated theological dogma from philosophical inquiry. Therefore, the Latin Averroist methodological doctrine of veritas duplex increased the autonomy of philosophical inquiry.
In what follows, I shall argue that despite possible appearances to the contrary, in its proper theoretical and historical context, the Latin Averroist methodological doctrine in fact delimited the autonomy of philosophical inquiry, while in the same context Aquinas's methodological conception of philosophy as the handmaiden of theology was not only much more beneficial for the autonomy of philosophical inquiry, but it was even suitable to prompt such genuine philosophical advances that the Averroistic conception would not have prompted at all.
When the autonomy of philosophy is considered in a medieval context, one thing should be clear at the outset. The autonomy of philosophy in that context could in no way mean the absolute independence of the results of philosophical inquiry from theological considerations. Accordingly, any medieval philosopher had to react somehow, whenever a perceived conflict between theology and philosophy emerged.
Another "methodological axiom" of the period is that when on account of such a conflict one of two incompatible propositions has to be denied, one of them being a theological and the other being a philosophical proposition, it is never the theological proposition that is to be denied, provided that it is an unambiguous expression of some revealed truth, or of some evident consequence thereof. Or, more briefly, revealed truth, coming directly from the First Truth (Veritas Prima), has absolute epistemic priority.
Accordingly, whenever a perceived conflict between faith and reason emerges, in keeping with these universally accepted general methodological principles the conflict cannot simply be ignored, and cannot be resolved by the denial of some revealed truth. But then, it seems that there is really little room left for a genuine resolution. For if the conflict is genuine, that is to say, if we find that a revealed truth, or a conclusion thereof, and a philosophical conclusion are such that the affirmation of the one along with unquestionably true premises validly entails the denial of the other, then the only move allowed by the above-described methodological principles is the denial of the philosophical conclusion. But then, if the philosophical conclusion is in fact a valid consequence of first philosophical principles, then this move at once entails the denial of at least one of these principles. However, how could this be allowed by a philosopher, whose first principles are self-evident truths, the denial of which directly runs counter to the very nature of human reason?
What I call for the purposes of this paper "the Averroistic conception" intends to resolve this further conflict by means of postulating a certain relative autonomy for human reason, in a manner analogous to the relative autonomy of natural agents. In keeping with this analogy, just as a natural agent has its proper operation determined by its own natural principles, so too reason has its proper operation guided by its own appropriate principles, namely, the first principles of philosophy. Furthermore, just as the proper operation of the natural agent regularly produces its appropriate effects assuming the common course of nature, while this operation can always be overruled by the operation of a superior agent, so too the proper operation of reason regularly produces its own appropriate effects, namely, the conclusions derived from its own rational principles, still, this operation can also be overruled by the principles belonging to a superior intellect, namely, the articles of faith revealed to us by the grace of the Divine Intellect.
The analogy might be tempting and it seems to suggest a genuine alternative for the autonomy of philosophy--however relative this autonomy might be--while at the same time preserving the due superiority of the articles of faith. For according to this conception what a philosopher qua philosopher has to do is simply to rely exclusively on the natural principles and operations of human reason, normally completely unaffected by any theological considerations. But when he perceives a conflict between some of the "products" of this operation (that is, some philosophical conclusion) and some article of faith, he simply needs to acknowledge the invalidity of this conclusion on account of the superiority of the article of faith, much in the way he would acknowledge a miracle that happens contrary to the ordinary workings of nature on account of the superiority of the supernatural agent that produced the miracle. To be sure, since the philosophical conclusion thus discarded was a consequence of self-evident principles of reason, its falsity should also falsify some of these principles, much in the way the operation of the superior agent would "invalidate" the natural principles of operation of the natural agent. But this falsification need not result in our discarding any of these principles; indeed, not any more than the occurrence of a miracle would eliminate the normal workings of natural agents under normal circumstances. On the contrary, the conflict can serve only as a reminder that these principles, however self-evident they are to us, can have only a restricted, relative validity, which can always be overruled by some higher principles. But as long as their validity is not subjected to such superior constraints, they do work well in producing their own consequences in exactly the same way as the principles of natural agents produce their own effects in accordance with their nature, indeed, just as they would always and necessarily produce their natural effects, were it not for the occasional, miraculous intervention of the superior agent.
As a matter of fact, in the framework of the Aristotelian theory of demonstration, these methodological considerations are not based on a mere analogy between the operating principles of natural causes and the rational principles of natural reason, but rather on a strict correspondence between the two kinds of principles, given that the demonstrations of natural reason proceed precisely from rational principles which refer to the operating principles of natural causes. Accordingly, when philosophical conclusions are based on such principles, the occasional conflict with faith can easily be resolved precisely with reference to the fact that the operations of natural causes can be miraculously overruled by a superior cause. Thus, in a commentary on the Physics, probably written by Siger of Brabant, we can read the following:
Ex hoc enim quod philosophus concludit aliquid esse necessarium vel impossibile per causas inferiores investigabiles ratione, non contradicit fidei, quae ponit illa posse aliter se habere per causam supremam, cuius virtus et causalitas non potest comprehendi ab aliqua creatura.
(The philosopher, when he concludes that something is necessary or impossible on the basis of inferior causes that can be investigated by reason, does not contradict faith, which asserts that those can be otherwise because of a supreme cause, whose power and causality cannot be comprehended by some creature.)
Or, as Boethius Dacus even more clearly states the same point:
Sic verum dicit christianus, dicens mundum et motum primum esse novum, et primum hominem fuisse, et hominem redire vivum et eundem numero, et rem generabilem fieri sine generatione, cum tamen hoc concedatur possibile esse per causam cuius virtus est maior, quam sit virtus causae naturalis; verum etiam dicit naturalis qui dicit hoc non esse possibile ex causis et principiis naturalibus: nam naturalis nihil concedit vel negat nisi ex principiis et causis naturalibus, sicut etiam nihil negat vel concedit grammaticus secundum quod huiusmodi nisi ex principiis et causis grammaticalibus.
(In this way the Christian states something true when he says that the world and the primary motion had a beginning, and that there was a first man, and that numerically the same man will be resurrected, and that a generable thing can come to be without generation; but this is conceded to be possible [only] for a superior cause, the power of which is greater than the power of a natural cause; however, the natural scientist will also state something true when he asserts that this is not possible by natural causes; for a natural scientist denies or concedes nothing, except on the basis of natural causes, just as a grammarian, as such, denies or concedes something only on the basis of grammatical principles and causes.)
Therefore, according to this conception it might even seem to be a simple mistake to be suspicious of philosophical conclusions contrary to faith, for we should all know and presuppose that the demonstrations of these philosophical conclusions have only a relative and limited validity, but not absolute validity, for they proceed only with the assumption of the undisturbed operation of natural causes. As Boethius Dacus wrote:
Et ista est causa deceptionis multorum qui credunt physicos velle simpliciter demonstrare conclusiones aliquas, cum demonstrant eas respectu quarum sive ex quarum suppositione impossibile est illas conclusiones aliter se habere.
(And this is the source of the error of many people who think that physicists would want to demonstrate some conclusions absolutely, for they demonstrate them [only] in respect of certain conditions, or with the supposition of certain assumptions, on the basis of which it is impossible for those conclusions to be otherwise.)
Now, however tempting this solution might appear, and however naturally it seems to provide room for the relative autonomy of philosophy, St. Thomas had good reasons to object to the methodology involved in it, not so much in the interest of faith against philosophy, but rather in the interest of philosophical inquiry itself.
As is well-known, St. Thomas had a very simple basis for asserting his position concerning the necessary concordance between faith and reason. As he most succinctly stated in the Summa contra Gentiles:
Quamvis autem praedicta veritas fidei christianae humanae rationis capacitatem excedat, haec tamen quae ratio naturaliter indita habet, huic veritati contraria esse non possunt. Ea enim quae naturaliter rationi sunt insita, verissima esse constat: in tantum ut nec esse falsa sit possibile cogitare. Nec id quod fide tenetur, cum tam evidenter divinitus confirmatum sit, fas est credere esse falsum. Quia igitur solum falsum vero contrarium est, ut ex eorum definitionibus inspectis manifeste apparet, impossibile est illis principiis quae ratio naturaliter cognoscit, praedictam veritatem fidei contrariam esse.
(Although the above-described truth of the Christian faith exceeds the capacity of human reason, nevertheless, those [principles] with which reason is naturally endowed cannot be contrary to this truth. For it is obvious that [the principles] which are naturally placed in reason are maximally true: so much so that it is not even possible to think that they are false. But neither is it viable to believe that which is held by faith to be false, given that it was so evidently confirmed by divine revelation. Since, therefore, only falsehood can be contrary to truth, as is manifestly clear from the consideration of their definitions, it is impossible that the principles naturally recognized by reason should be contrary to the above-mentioned truth of faith.)
That is to say, since both the principles of reason and the articles of faith are necessarily true, while truths can imply only truths, and no truths are contrary to any truths, there cannot be a conflict between faith and reason in the sense that either a truth of reason or a truth of faith could ever entail the denial of the other.
But then how can it happen that philosophers apparently draw many conclusions from truths of reason which are clearly contrary to some articles of faith?
St. Thomas's answer is quite simple again. When philosophers appear to conclude to claims contrary to the truths of faith, they are simply mistaken:
Ex quo evidenter colligitur, quaecumque argumenta contra fidei documenta ponantur, haec ex principiis primis naturae inditis per se notis non recte procedere. Unde nec demonstrationis vim habent, sed vel sunt rationes probabiles vel sophisticae. Et sic ad ea solvenda locus relinquitur.
(And from this it is evidently concluded that any arguments propounded against the teachings of faith do not correctly proceed from the first, self-evident principles inscribed in our nature. Therefore, they do not have the efficacy of demonstrations, but they are either probable, or sophistic arguments. Hence room is left for their refutation.)
Indeed, if there is a genuine conflict between conclusions derived from faith and the principles of philosophy, the source of the conflict is not to be sought in the genuine principles of philosophy, but rather in the defective use of the principles of philosophy:
Si quid autem in dictis philosophorum invenitur contrarium fidei, hoc non est philosophia, sed magis philosophiae abusus ex defectu rationis. Et ideo possibile est ex principiis philosophiae huiusmodi errorem refellere vel ostendendo omnino esse impossibile vel ostendendo non esse necessarium.
(But if one finds among the claims of the philosophers something that is contrary to faith, that is not philosophy, but rather the abuse of philosophy stemming from the defectiveness of reasoning. And so it is possible to refute such an error, either by showing that it is entirely impossible, or by showing that it is not necessary.)
What is most important from our point of view here is St. Thomas's insistence that whenever a perceived conflict emerges, since what caused the conflict was a mistake in the use of philosophical principles in the first place, the resolution of the conflict is but a further philosophical task. But we have every reason to be confident that this philosophical task can be carried out, for we know that the truths of faith never invalidate any genuine, true philosophical principle:
... dona gratiarum hoc modo naturae adduntur quod eam non tollunt, sed magis perficiunt; unde et lumen fidei, quod nobis gratis infunditur, non destruit lumen naturalis rationis divinitus nobis inditum. Et quamvis lumen naturale mentis humanae sit insufficiens ad manifestationem eorum quae manifestantur per fidem, tamen impossibile est quod ea, quae per fidem traduntur nobis divinitus, sint contraria his quae sunt per naturam nobis indita. Oporteret enim alterum esse falsum; et cum utrumque sit nobis a deo, deus nobis esset auctor falsitatis, quod est impossibile.
(... the gifts of grace are added to nature in such a fashion that they do not eliminate it, but rather perfect it; hence the light of faith, which is infused into us by grace, does not destroy the light of reason divinely bestowed on us. And even though the natural light of the human mind is insufficient for the manifestation of those [truths] that are manifested by faith, it is nevertheless impossible that those [truths] that are divinely taught to us by faith should be contrary to those that are given to us by nature. For then one of these would have to be false, and since we have both from God, God would be the teacher of some falsehood to us, and this is impossible.)
That is to say, since we know that both the natural principles of reason and the supernatural principles of revelation, both coming from the First Truth, have to be true, we should also know that it is impossible for a genuine conflict to emerge between the two. Therefore, whenever an apparent conflict emerges, we have the genuinely philosophical task of detecting the fallacy that accounts for the illusion. But since in this process no genuine philosophical principle is ever invalidated, we know that all we have to deal with is the correction of ordinary human error, which we know can safely be carried out by applying the ordinary self-correcting mechanisms of natural reason, namely, philosophical analysis in philosophical disputations.
Perhaps, on the basis of this brief side-by-side presentation of the two methodological conceptions, it is already clear what we should, and what we should not regard as the fundamental difference between the two, and why I can claim on this basis that in the given historical and theoretical context Aquinas's conception provided greater room for philosophical inquiry than the Averroistic conception did.
For the difference is obviously not that while the Averroistic conception would assert the validity of philosophical conclusions despite their conflict with faith, Aquinas's conception would impose theological dogma on philosophical inquiry by denying the validity of philosophical conclusions, and hence the principles from which they follow, because of their conflict with faith.
To be sure, at one place Boethius Dacus appears to suggest that a philosopher should maintain his position even despite its conflict with faith:
Veritatem tamen illam quam ex suis principiis causare non potest nec scire, quae tamen contrariatur suis principiis et destruit suam scientiam, negare debet, quia sicut consequens ex principiis est concedendum, sic repugnans est negandum ...
(But he has to deny that truth which he can neither cause nor know on the basis of his principles, and which is contrary to his principles and destroys his science; for just as one has to concede that which follows from one's principles, so also one has to deny that which is incompatible with these principles.)
But then he immediately goes on to qualify what he just said:
ista debet negare naturalis, quia naturalis nihil concedit, nisi quod videt esse possibile per causas naturales
(the natural scientist has to deny these claims, for a natural scientist concedes nothing, except that which he sees to be possible by natural causes)
And afterwards, in reply to the question whether in this case the natural scientist would assert something false, he says:
quicquid enim naturalis, secundum quod naturalis, negat vel concedit, ex causis et principiis naturalibus hoc negat vel concedit. Unde conclusio in qua naturalis dicit mundum et primum motum non esse novum, accepta absolute, falsa est, sed si referatur in rationes et principia ex quibus ipse eam concludit, ex illis sequitur.
(For anything denied or conceded by a natural scientist, insofar as he is a natural scientist, is denied or conceded by him on the basis of natural causes. Hence the conclusion by means of which the natural scientist states that the world and the primary motion did not have a beginning, taken absolutely, is false, but if it is referred to the arguments and principles from which he concluded to it, it does follow from them.)
That is to say, the natural philosopher's denial of an article of faith, or, equivalently, his assertion of the contrary conclusion, according to this conception amounts to nothing more than the assertion that the proposition contrary to faith follows from his principles. But as far as the truth or falsity of his conclusion is concerned, absolutely speaking, regardless of what it followed from, Boethius declares that the conclusion has to be claimed to be false, precisely and exclusively because it is contrary to faith. But then, the inevitable consequence of this position is that if this conclusion is indeed a valid consequence of philosophical principles, then at least one of these principles will also have to be asserted to be absolutely false. And so, the further inevitable conclusion is that in view of the truths of faith, philosophy must be radically flawed, involving some absolute falsity among its genuine first principles. However, this is precisely the point on which Aquinas would disagree, for, as we could see, according to his position concerning philosophical principles, no genuine philosophical principle can ever turn out to be false.
Therefore, on this basis we can state that the fundamental difference between Aquinas's and the Averroistic conception is that while the Averroistic conception maintains only a rather shaky and precarious autonomy of philosophy, allowing that even its genuine principles can always be overruled by the authority of theological truth, Aquinas's position allows for the much safer autonomy of philosophy by proclaiming the absolute validity of its genuine principles, and by relegating the apparent conflicts between faith and reason to the sphere of simple human error, detectable precisely by means of these principles. So, in fact it is rather the Averroistic conception that imposes dogma upon philosophical inquiry, indeed, so much so that it even allows the falsification of its genuine first principles precisely and exclusively on account of their conflict with faith.
By contrast, Aquinas's conception never allows the position that genuine philosophical principles could ever be falsified on the basis of their conflict with faith, because according to his position there can never be such a genuine conflict in the first place. But if an apparent conflict emerges, then this is only a new challenge for the philosopher, as such, to check the validity of his arguments and of his premises, for even if he finds that the conclusion validly follows from the actual premises, he may as well find that what he took to be self-evident philosophical principles figuring as the premises of his arguments were in fact only some false propositions that he mistook for self-evident principles. In this way the philosophical re-examination of his arguments and his premises is even likely to produce such philosophical results which would simply be ignored on the basis of the Averroistic methodology.
In fact, this is precisely what we can detect in Aquinas's handling of a number of issues in which there appears to be a conflict between philosophical principles and articles of faith. Perhaps, this is the clearest in the case of the apparent conflict between the theological doctrine of the Holy Eucharist, according to which the accidents of wine and bread should exist there miraculously without a subject, and the Aristotelian definition of accident, according to which an accident by definition is something that exists in a subject. For given this definition, the claim that an accident is not in a subject would entail the contradiction that the same thing is both an accident and not an accident, whereas a contradiction cannot be made true even by divine omnipotence.
The way in which Aquinas resolves this apparent conflict is perhaps one of the best illustrations of his general methodology. Rather than simply claiming that in this case omnipotence overrules ordinary principles of reason (well, indeed, this would be a tough call where the first principle, the principle of non-contradiction is concerned), he provides Avicenna's philosophical analysis of whether the notion of being can figure in a definition as a reason for re-examining the definition of accident as it is usually quoted. As a result of this re-examination he ends up with a refined, philosophically clarified definition, which not only provides us with a solution (by showing that the positing of accidents without a subject miraculously sustained by divine power is not self-contradictory), but also with a general insight into how the quiddities of various sorts of entities signified by their essential definitions are related to their modes of being, which then also influences the treatment of a number of other purely philosophical questions, such as the question of the nature and mode of being of the human soul.
By contrast, in discussing the question whether an accident would in this way be separable, Siger simply states that given the definition of accident this is impossible, while at the same time he acknowledges that it is miraculously possible, leaving the emerging philosophical conflict, namely, his claim's conflict with the principle of non-contradiction, simply unresolved.
But in accordance with the common philosophical slogan, based on Aristotle's remarks at the beginning of bk. 3 of the Metaphysics, "the resolution of doubts is the manifestation of truth" (dubiorum solutio est veritatis manifestatio), and so the unresolved doubts prevent the manifestation of truth. Indeed, leaving the above-mentioned conflict unresolved leaves us only with an inconsistent set of propositions. However, because we know that they are inconsistent, we also know that at least one of these has to be false. Therefore, whoever asserts all these propositions together, knowingly states something false, and if he does so from a university cathedra, he becomes a falsus doctor, who is morally responsible for his false teachings. So no wonder that in one of his sermons Thomas expresses moral outrage over the procedure in which the masters of Arts are trying to avoid the burden of this responsibility by their usual disclaimers, attributing the claims contrary to faith to someone else, usually to Aristotle:
Inveniuntur aliqui qui student in philosophia, et dicunt aliqua quae non sunt vera secundum fidem; et cum dicitur eis quod hoc repugnat fidei, dicunt quod philosophus dicit hoc, sed ipsi non asserunt: imo solum recitant verba philosophi. Talis est falsus propheta, sive falsus doctor, quia idem est dubitationem movere et eam non solvere quod eam concedere.
(There are some people who work in philosophy and state some things that are not true according to the faith; and when they are told that this is incompatible with faith, they reply that this is a claim of the philosopher, nevertheless, they do not assert it, but rather they merely recite the words of the philosopher. Such is the false prophet, or the false teacher: for it is the same thing to raise a doubt without resolving it and to concede it.)
The main point here is that the usual disclaimers of the masters of Arts--whether they are sincere or not--simply assert the superiority of faith, but leave the inconsistency between their principles and the articles of faith philosophically unresolved. Therefore, their teaching definitely has to involve some falsity, whether they are willing to take personal responsibility for it by asserting it ex persona sua or not, and so Thomas's outrage is completely understandable.
But in fact this outrage did not have to be motivated by a need to defend the faith--after all, the Arts masters were always quick to subject whatever they taught to the authority of the Church--, but much rather by a need to defend philosophy. As we could see, the Averroistic methodological conception leaves the conflicts between faith and philosophy radically unresolved. The further maneuvers involving the usual disclaimers, attributing the conflicting claims to Aristotle, or even to the philosophical principles themselves from which such conclusions follow only worsen the situation. For by these disclaimers the masters of Arts simply testify that the Philosopher and his philosophical principles, or indeed, the principles of natural reason in general, are essentially flawed, and can easily lead anyone following them astray, insofar as they can lead to conclusions genuinely opposed to the revealed truth faith. But from here it is just one easy step for university authorities--known since the dawn of universities up to the present time for handling moot academic questions with radical administrative "solutions"--to eliminate such a dangerous and radically flawed discipline from the curriculum altogether. So the Averroistic conception in the given historical context involved not only a theoretical limitation upon the autonomy of philosophy by simply subjecting the validity of its principles to the authority of faith, but also a serious practical threat to the very existence of the doctrine in the curriculum. But then, in view of these considerations I think we can safely conclude that the freedom of the handmaiden in her reliable handling of her own business proclaimed by the philosopher-saint did in fact involve a much greater autonomy than the precarious rule of the lady of the philosophers.
 As Godefroid de Fontaines in his abbreviation of Boethius Dacus's De Aeternitate mundi put it: "volentes sententiam fidei de aeternitate mundi et sententiam philosophorum ad concordiam reducere, ut sententia fidei firmiter teneatur, quamquam demonstrari non possit, et ut sententia philosophorum salvetur, quantum ratio eorum concludere potest--nam eorum sententia fidei non contradicit, quia innititur demonstrationibus et certis rationibus possibilibus in rebus, de quibus loquuntur, fides autem in multis innititur miraculis et revelationibus et non rationibus; quod enim teneatur propter hoc quod ratione conclusum est, non est fides, sed scientia--et ut pateat quod rationes per quas haeretici tenent mundum esse aeternum vigorem non habent. [...] Quod autem naturalis per rationes non possit demonstrare motum primum et mundum esse novum patet, quia nullus artifext potest aliquid causare, concedere vel negare nisi ex principiis suae scientiae." Godefroid de Fontaines: "Abrégé du De Aeternitate Mundi", in: Boethii Daci Opera: Opuscula, ed. N. Green-Pedersen, Hauniae: Apud Librarium G.E.C. Gad, 1976, p. 435. Cf.: "nullus artifex considerare potest illa quae sunt extra terminos suae scientiae". Boethius Dacus: Modi significandi sive Quaestiones super Priscianum, in: Boethii Daci Opera, ed. J. Pinborg et H. Roos, Hauniae : Det Danske Sprog- og Litteraturselskab, p. 46.
 Ein Kommentar zur Physik des Aristoteles aus der Pariser Artistenfakultat um 1273, ed. A. Zimmermann, Berlin: De Gruyter,1968, p. 3.
 Boetii de Dacia tractatus De aeternitate mundi, ed., Sajo, G., Berlin, De. Gruyter, Quellen und Studien zur Geschichte der Philosophie ; Bd. 4, 1964, pp. 46-48.
 Namely, the motion of the sphere of the fixed stars upon which all other motions depend.
 "De somniis", in: Boethii Daci Opera: Opuscula, ed. N. Green-Pedersen, Hauniae: Apud Librarium G.E.C. Gad, 1976, p. 387.
 SCG lb. 1, c. 7.
 In Librum Boethii De Trinitate, prooem., q. 2, a. 3.
 Boetii de Dacia tractatus De aeternitate mundi, ed., Sajo, G., Berlin, De. Gruyter, Quellen und Studien zur Geschichte der Philosophie ; Bd. 4, 1964.
 "Praeterea, de eodem praedicatur definitio et definitum. Sed ens per se est definitio vel descriptio substantiae. Si ergo in sacramento altaris accidentia sunt per se non in subiecto, sequitur quod sint substantiae; quod est absurdum." QDL 9, q. 3, obj. 2; "Praeterea, quicumque separat definitionem a definito, ponit duo contradictoria esse simul vera: quia hoc ipsum quod est homo, est animal rationale mortale; et ita si ponatur esse homo et non esse animal rationale mortale, ponitur esse homo et non esse. Sed definitio accidentis est quod inest substantiae; unde etiam in definitione singulorum accidentium oportet quod ponatur substantia. Ergo cum deus non possit facere contradictoria simul esse vera, neque facere poterit quod accidens sit sine substantia." 4SN, d. 12, q. 1, a. 1a, obj. 2
 "Ad secundum dicendum, quod secundum Avicennam in sua Metaph., esse non potest poni in definitione alicuius generis et speciei, quia omnia particularia uniuntur in definitione generis vel speciei, cum tamen genus vel species non sit secundum unum esse in omnibus. Et ideo haec non est vera definitio substantiae: substantia est quod per se est; vel: accidens est quod est in alio. Sed est circumlocutio verae descriptionis, quae talis intelligitur: substantia est res cuius naturae debetur esse non in alio; accidens vero est res, cuius naturae debetur esse in alio. Unde patet quod, quamvis accidens miraculose sit non in subiecto, non tamen pertinet ad definitionem substantiae; non enim per hoc eius naturae debetur esse non in alio; nec egreditur definitionem accidentis, quia adhuc natura eius remanet talis ut ei debeatur esse in alio." QDL 9, q. 3, ad 2-um; "Ad secundum dicendum, quod sicut probat Avicenna in sua Metaph., per se existere non est definitio substantiae: quia per hoc non demonstratur quidditas ejus, sed ejus esse; et sua quidditas non est suum esse; alias non posset esse genus: quia esse non potest esse commune per modum generis, cum singula contenta in genere differant secundum esse; sed definitio, vel quasi definitio, substantiae est res habens quidditatem, cui acquiritur esse, vel debetur, ut non in alio; et similiter esse in subjecto non est definitio accidentis, sed e contrario res cui debetur esse in alio; et hoc nunquam separatur ab aliquo accidente, nec separari potest: quia illi rei quae est accidens, secundum rationem suae quidditatis semper debetur esse in alio. Sed potest esse quod illud quod debetur alicui secundum rationem suae quidditatis, ei virtute divina agente non conveniat; et sic patet quod facere accidens esse sine substantia, non est separare definitionem a definito; et si aliquando hoc dicatur definitio accidentis, praedicto modo intelligenda est definitio dicta: quia aliquando ab auctoribus definitiones ponuntur causa brevitatis non secundum debitum ordinem, sed tanguntur illa ex quibus potest accipi definitio." 4SN, d. 12, q. 1, a. 1a, ad 2-um
 Cf. SCG lb. 2, cc. 68-70; QDA a. 1, ad 9-um et 10-um; QDL 10, q. 3, a. 2, ad 3-um et 4-um.
 "Unde sophistice quidam arguunt credentes naturali ratione ostendere et demonstrare quod causa prima possit facere quod accidens existat sine subiecto illius accidentis, propter hoc quod causa prima est causa omnium causarum mediarum accidentis inter ipsam et accidens, et ideo sola facere possit quod existat accidens, quamquam accidenti nulla existat aliarum causarum accidentis; et cum substantia sit aliqua causa accidentis, poterit facere ut sine substantia subsistat accidens. Ratio, ut manifeste apparet, deficit secundum ea quae prius dicta sunt. Ut tamen sane intelligatur, sciendum est quod primariam causam posse facere accidens existere sine subiecto illius accidentis confitemur. Hoc tamen est non propter istam rationem: est enim oratio conclusa peior seipsa non conclusa." Les Quaestiones super Librum de Causis de Siger de Brabant, ed. Marsala, A., Publications Universitaires: Louvain, Béatrice-Nauwelaerts: Paris, 1972, p. 41. Cf.: "Ad tertium dicendum, quod deus potest omne, quod habet rationem possibilis simpliciter. Est autem possibile de aliquo solum quod non est contrarium suae rationi. Cum ergo non esse in subiecto sit contrarium rationi accidentis, non habet rationem possibilis, sed impossibilis contradictionem implicantis, cum ratio accidentis secundum Philosophum sit non tantum, ut aptum natum sit esse in subiecto, sed ut sit in subiecto. Nec apparet aliqua, quae aliquando sunt in subiecto, aliquando exsistere sine subiecto lumine rationis naturalis, licet per miraculum credendum sit hoc posse fieri. Substantia enim est causa materialis accidentis, et hoc modo deus non <est> causa accidentis. Non oportet autem, si deus potest facere aliquem effectum mediante eius causa, causa aliqua, quae est illius forma vel materia, quod possit ilium effectum facere per se. Tunc enim contingeret, quod exsistentia solius dei exsisterent omnia entia in propriis eorum naturis et secundum eorum proprias rationes. Non oportet etiam, quod illud, quod potest causa primaria efficiens mediante secundaria efficiente, quod illud possit sine secundaria, eo quod effectus non fit sine causa ad effectum illum determinata potius quam ad oppositum. Primaria autem sic per secundarias determinatur." Ein Kommentar zur Physik des Aristoteles aus der Pariser Artistenfakultat um 1273, ed. A. Zimmermann, Berlin: De Gruyter, 1968, p. 25.
 Ironically, Siger himself begins his commentary on the Liber de Causis precisely by alluding to these remarks of Aristotle's: "Sicut vult Aristoteles in principio tertii Metaphysicae, volentes attingere ad cognitionem veritatis in aliquibus rebus absque cognitione eorum quae dubitationein inducunt in cognitionem veritatis illarum rerum, similes sunt incedentibus nescientibus tamen ad quem locum ire debeant. Cuius ratio est, quia absolutio dubitationis finis est tendentis ad veritatem; et ideo, sicut qui nescit locum non veniet ad ipsum nisi casu, et cum ad ipsum venerit nesciet ipsum esse locum quo tendebat, et ideo ignorabit utrum sit ibi quiescendum vel ulterius procedendum, sic non praeconcipiens dubitationes ad cognitionem veritatis non dirigetur nisi casu, quia, si veritatem attigerit, nesciet utrum ibi quiescendum vel ulterius procedendum. Et dubitans etiam similis est ligato vinculo corporali qui, si ligamentum ignoraverit, ipsum dissolvere non valebit. Dubitatio enim mentem tenet ne ulterius per considerationem procedere possit, sicut vinculo corporali pedes tenentur; et ideo dubitationes non praeconsiderans non valet absolvere dubitationes; quare nec attingere ad veritatem. Cognitio enim veritatis in aliqua rerum solutio est dubitatorum. Et sicut in iudiciis dicitur quod melius contingit iudicare audiendo rationes utriusque partis, similiter etiam praeconsideratis rationibus ad utramque partem contradictionis dubitationem in aliquo inducentibus melius contingit iudicare veritatem." Les Quaestiones super Librum de Causis de Siger de Brabant, ed. Marsala, A., Publications Universitaires: Louvain, Béatrice-Nauwelaerts: Paris, 1972, p. 35.
 Attendite a falsis prophetis, Sermones, n. 2.
 The main argument of this paper grew out of a discussion with a young Hungarian mediaevalist, Gábor Borbély. The discussion originally started out as the formal dispute of the public defense of his Ph.D. thesis at the Hungarian Academy in 1994. Despite our disagreement concerning the evaluation of the relative merits and demerits of the two methodological conceptions discussed here, the present paper owes a great deal, especially in the presentation of the "Averroistic conception", to this discussion. Gábor Borbély's thesis, containing an annotated Hungarian translation of Aquinas's De Unitate Intellectus along with a doctrinal introduction, was published in Hungary under the title: Az értelem egységéről, Matúra: Budapest, 1993.