Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that the intellectual principle is not multiplied according to the number of bodies, but that there is one intellect in all men. For an immaterial substance is not multiplied in number within one species. But the human soul is an immaterial substance; since it is not composed of matter and form as was shown above (Question 75, Article 5). Therefore there are not many human souls in one species. But all men are of one species. Therefore there is but one intellect in all men.

Objection 2: Further, when the cause is removed, the effect is also removed. Therefore, if human souls were multiplied according to the number of bodies, it follows that the bodies being removed, the number of souls would not remain; but from all the souls there would be but a single remainder. This is heretical; for it would do away with the distinction of rewards and punishments.

Objection 3: Further, if my intellect is distinct from your intellect, my intellect is an individual, and so is yours; for individuals are things which differ in number but agree in one species. Now whatever is received into anything must be received according to the condition of the receiver. Therefore the species of things would be received individually into my intellect, and also into yours: which is contrary to the nature of the intellect which knows universals.

Objection 4: Further, the thing understood is in the intellect which understands. If, therefore, my intellect is distinct from yours, what is understood by me must be distinct from what is understood by you; and consequently it will be reckoned as something individual, and be only potentially something understood; so that the common intention will have to be abstracted from both; since from things diverse something intelligible common to them may be abstracted. But this is contrary to the nature of the intellect; for then the intellect would seem not to be distinct from the imagination. It seems, therefore, to follow that there is one intellect in all men.

Objection 5: Further, when the disciple receives knowledge from the master, it cannot be said that the master's knowledge begets knowledge in the disciple, because then also knowledge would be an active form, such as heat is, which is clearly false. It seems, therefore, that the same individual knowledge which is in the master is communicated to the disciple; which cannot be, unless there is one intellect in both. Seemingly, therefore, the intellect of the disciple and master is but one; and, consequently, the same applies to all men.

Objection 6: Further, Augustine (De Quant. Animae xxxii) says: "If I were to say that there are many human souls, I should laugh at myself." But the soul seems to be one chiefly on account of the intellect. Therefore there is one intellect of all men.

On the contrary, The Philosopher says (Phys. ii, 3) that the relation of universal causes to universals is like the relation of particular causes to individuals. But it is impossible that a soul, one in species, should belong to animals of different species. Therefore it is impossible that one individual intellectual soul should belong to several individuals.

I answer that, It is absolutely impossible for one intellect to belong to all men. This is clear if, as Plato maintained, man is the intellect itself. For it would follow that Socrates and Plato are one man; and that they are not distinct from each other, except by something outside the essence of each. The distinction between Socrates and Plato would be no other than that of one man with a tunic and another with a cloak; which is quite absurd.

It is likewise clear that this is impossible if, according to the opinion of Aristotle (De Anima ii, 2), it is supposed that the intellect is a part or a power of the soul which is the form of man. For it is impossible for many distinct individuals to have one form, as it is impossible for them to have one existence, for the form is the principle of existence.

Again, this is clearly impossible, whatever one may hold as to the manner of the union of the intellect to this or that man. For it is manifest that, supposing there is one principal agent, and two instruments, we can say that there is one agent absolutely, but several actions; as when one man touches several things with his two hands, there will be one who touches, but two contacts. If, on the contrary, we suppose one instrument and several principal agents, we might say that there are several agents, but one act; for example, if there be many drawing a ship by means of a rope; there will be many drawing, but one pull. If, however, there is one principal agent, and one instrument, we say that there is one agent and one action, as when the smith strikes with one hammer, there is one striker and one stroke. Now it is clear that no matter how the intellect is united or coupled to this or that man, the intellect has the precedence of all the other things which appertain to man; for the sensitive powers obey the intellect, and are at its service. Therefore, if we suppose two men to have several intellects and one sense---for instance, if two men had one eye---there would be several seers, but one sight. But if there is one intellect, no matter how diverse may be all those things of which the intellect makes use as instruments, in no way is it possible to say that Socrates and Plato are otherwise than one understanding man. And if to this we add that to understand, which is the act of the intellect, is not affected by any organ other than the intellect itself; it will further follow that there is but one agent and one action: that is to say that all men are but one "understander," and have but one act of understanding, in regard, that is, of one intelligible object.

However, it would be possible to distinguish my intellectual action form yours by the distinction of the phantasms---that is to say, were there one phantasm of a stone in me, and another in you---if the phantasm itself, as it is one thing in me and another in you, were a form of the possible intellect; since the same agent according to divers forms produces divers actions; as, according to divers forms of things with regard to the same eye, there are divers visions. But the phantasm itself is not a form of the possible intellect; it is the intelligible species abstracted from the phantasm that is a form. Now in one intellect, from different phantasms of the same species, only one intelligible species is abstracted; as appears in one man, in whom there may be different phantasms of a stone; yet from all of them only one intelligible species of a stone is abstracted; by which the intellect of that one man, by one operation, understands the nature of a stone, notwithstanding the diversity of phantasms. Therefore, if there were one intellect for all men, the diversity of phantasms which are in this one and that one would not cause a diversity of intellectual operation in this man and that man. It follows, therefore, that it is altogether impossible and unreasonable to maintain that there exists one intellect for all men.

Reply to Objection 1: Although the intellectual soul, like an angel, has no matter from which it is produced, yet it is the form of a certain matter; in which it is unlike an angel. Therefore, according to the division of matter, there are many souls of one species; while it is quite impossible for many angels to be of one species.

Reply to Objection 2: Everything has unity in the same way that it has being; consequently we must judge of the multiplicity of a thing as we judge of its being. Now it is clear that the intellectual soul, by virtue of its very being, is united to the body as its form; yet, after the dissolution of the body, the intellectual soul retains its own being. In like manner the multiplicity of souls is in proportion to the multiplicity of the bodies; yet, after the dissolution of the bodies, the souls retain their multiplied being.

Reply to Objection 3: Individuality of the intelligent being, or of the species whereby it understands, does not exclude the understanding of universals; otherwise, since separate intellects are subsistent substances, and consequently individual, they could not understand universals. But the materiality of the knower, and of the species whereby it knows, impedes the knowledge of the universal. For as every action is according to the mode of the form by which the agent acts, as heating is according to the mode of the heat; so knowledge is according to the mode of the species by which the knower knows. Now it is clear that common nature becomes distinct and multiplied by reason of the individuating principles which come from the matter. Therefore if the form, which is the means of knowledge, is material---that is, not abstracted from material conditions---its likeness to the nature of a species or genus will be according to the distinction and multiplication of that nature by means of individuating principles; so that knowledge of the nature of a thing in general will be impossible. But if the species be abstracted from the conditions of individual matter, there will be a likeness of the nature without those things which make it distinct and multiplied; thus there will be knowledge of the universal. Nor does it matter, as to this particular point, whether there be one intellect or many; because, even if there were but one, it would necessarily be an individual intellect, and the species whereby it understands, an individual species.

Reply to Objection 4: Whether the intellect be one or many, what is understood is one; for what is understood is in the intellect, not according to its own nature, but according to its likeness; for "the stone is not in the soul, but its likeness is," as is said, De Anima iii, 8. Yet it is the stone which is understood, not the likeness of the stone; except by a reflection of the intellect on itself: otherwise, the objects of sciences would not be things, but only intelligible species. Now it happens that different things, according to different forms, are likened to the same thing. And since knowledge is begotten according to the assimilation of the knower to the thing known, it follows that the same thing may happen to be known by several knowers; as is apparent in regard to the senses; for several see the same color, according to different likenesses. In the same way several intellects understand one object understood. But there is this difference, according to the opinion of Aristotle, between the sense and the intelligence---that a thing is perceived by the sense according to the disposition which it has outside the soul ---that is, in its individuality; whereas the nature of the thing understood is indeed outside the soul, but the mode according to which it exists outside the soul is not the mode according to which it is understood. For the common nature is understood as apart from the individuating principles; whereas such is not its mode of existence outside the soul. But, according to the opinion of Plato, the thing understood exists outside the soul in the same condition as those under which it is understood; for he supposed that the natures of things exist separate from matter.

Reply to Objection 5: One knowledge exists in the disciple and another in the master. How it is caused will be shown later on (Question 117, Article 1).

Reply to Objection 6: Augustine denies a plurality of souls, that would involve a plurality of species.

Articulus 2

Argumentum 1

Ad secundum sic proceditur. Videtur quod intellectivum principium non multiplicetur secundum multiplicationem corporum, sed sit unus intellectus in omnibus hominibus.

Nulla enim substantia immaterialis multiplicatur secundum numerum in una specie. Anima autem humana est substantia immaterialis, non enim est composita ex materia et forma, ut supra ostensum est.

Non ergo sunt multae in una specie. Sed omnes homines sunt unius speciei.

Est ergo unus intellectus omnium hominum.

Argumentum 2

Praeterea, remota causa, removetur effectus. Si ergo secundum multiplicationem corporum multiplicarentur animae humanae, consequens videretur quod, remotis corporibus, multitudo animarum non remaneret, sed ex omnibus animabus remaneret aliquod unum solum. Quod est haereticum, periret enim differentia praemiorum et poenarum.

Argumentum 3

Praeterea, si intellectus meus est alius ab intellectu tuo, intellectus meus est quoddam individuum, et similiter intellectus tuus, particularia enim sunt quae differunt numero et conveniunt in una specie. Sed omne quod recipitur in aliquo, est in eo per modum recipientis. Ergo species rerum in intellectu meo et tuo reciperentur individualiter, quod est contra rationem intellectus, qui est cognoscitivus universalium.

Argumentum 4

Praeterea, intellectum est in intellectu intelligente. Si ergo intellectus meus est alius ab intellectu tuo, oportet quod aliud sit intellectum a me, et aliud sit intellectum a te. Et ita erit individualiter numeratum, et intellectum in potentia tantum, et oportebit abstrahere intentionem communem ab utroque, quia a quibuslibet diversis contingit abstrahere aliquod commune intelligibile. Quod est contra rationem intellectus, quia sic non videretur distingui intellectus a virtute imaginativa. Videtur ergo relinqui quod sit unus intellectus omnium hominum.

Argumentum 5

Praeterea, cum discipulus accipit scientiam a magistro, non potest dici quod scientia magistri generet scientiam in discipulo, quia sic etiam scientia esset forma activa, sicut calor; quod patet esse falsum. Videtur ergo quod eadem numero scientia quae est in magistro, communicetur discipulo. Quod esse non potest, nisi sit unus intellectus utriusque. Videtur ergo quod sit unus intellectus discipuli et magistri; et per consequens omnium hominum.

Argumentum 6

Praeterea, Augustinus dicit, in libro de quantitate animae, si plures tantum animas humanas dixerim, ipse me ridebo.

Sed maxime videtur anima esse una quantum ad intellectum.

Ergo est unus intellectus omnium hominum.

Sed Contra

Sed contra est quod philosophus dicit, in II physic., quod sicut se habent causae universales ad universalia, ita se habent causae particulares ad particularia.

Sed impossibile est quod una anima secundum speciem, sit diversorum animalium secundum speciem. Ergo impossibile est quod anima intellectiva una numero, sit diversorum secundum numerum.

Corpus

Respondeo dicendum quod intellectum esse unum omnium hominum, omnino est impossibile.

Et hoc quidem patet, si, secundum Platonis sententiam homo sit ipse intellectus.

Sequeretur enim, si socratis et Platonis est unus intellectus tantum, quod socrates et Plato sint unus homo; et quod non distinguantur ab invicem nisi per hoc quod est extra essentiam utriusque. Et erit tunc distinctio socratis et Platonis non alia quam hominis tunicati et cappati, quod est omnino absurdum.

Similiter etiam patet hoc esse impossibile, si, secundum sententiam Aristotelis, intellectus ponatur pars, seu potentia, animae quae est hominis forma.

Impossibile est enim plurium numero diversorum esse unam formam, sicut impossibile est quod eorum sit unum esse, nam forma est essendi principium. Similiter etiam patet hoc esse impossibile quocumque modo quis ponat unionem intellectus ad hunc et ad illum hominem. Manifestum est enim quod, si sit unum principale agens et duo instrumenta, dici poterit unum agens simpliciter, sed plures actiones, sicut si unus homo tangat diversa duabus manibus, erit unus tangens, sed duo tactus. Si vero e converso instrumentum sit unum et principales agentes diversi, dicentur quidem plures agentes, sed una actio, sicut si multi uno fune trahant navem, erunt multi trahentes, sed unus tractus. Si vero agens principale sit unum et instrumentum unum, dicetur unum agens et una actio, sicut cum faber uno martello percutit, est unus percutiens et una percussio.

Manifestum est autem quod, qualitercumque intellectus seu uniatur seu copuletur huic vel illi homini, intellectus inter cetera quae ad hominem pertinent, principalitatem habet, obediunt enim vires sensitivae intellectui, et ei deserviunt. Si ergo poneretur quod essent plures intellectus et sensus unus duorum hominum, puta si duo homines haberent unum oculum; essent quidem plures videntes, sed una visio. Si vero intellectus est unus, quantumcumque diversificentur alia quibus omnibus intellectus utitur quasi instrumentis, nullo modo socrates et Plato poterunt dici nisi unus intelligens. Et si addamus quod ipsum intelligere, quod est actio intellectus, non fit per aliquod aliud organum, nisi per ipsum intellectum; sequetur ulterius quod sit et agens unum et actio una; idest quod omnes homines sint unus intelligens, et unum intelligere; dico autem respectu eiusdem intelligibilis.

Posset autem diversificari actio intellectualis mea et tua per diversitatem phantasmatum, quia scilicet aliud est phantasma lapidis in me et aliud in te, si ipsum phantasma, secundum quod est aliud in me et aliud in te, esset forma intellectus possibilis, quia idem agens secundum diversas formas producit diversas actiones, sicut secundum diversas formas rerum respectu eiusdem oculi sunt diversae visiones. Sed ipsum phantasma non est forma intellectus possibilis, sed species intelligibilis quae a phantasmatibus abstrahitur. In uno autem intellectu a phantasmatibus diversis eiusdem speciei non abstrahitur nisi una species intelligibilis. Sicut in uno homine apparet, in quo possunt esse diversa phantasmata lapidis, et tamen ab omnibus eis abstrahitur una species intelligibilis lapidis, per quam intellectus unius hominis operatione una intelligit naturam lapidis, non obstante diversitate phantasmatum. Si ergo unus intellectus esset omnium hominum, diversitas phantasmatum quae sunt in hoc et in illo, non posset causare diversitatem intellectualis operationis huius et illius hominis, ut Commentator fingit in III de anima.

Relinquitur ergo quod omnino impossibile et inconveniens est ponere unum intellectum omnium hominum.

Ad 1

Ad primum ergo dicendum quod, licet anima intellectiva non habeat materiam ex qua sit, sicut nec Angelus, tamen est forma materiae alicuius; quod Angelo non convenit. Et ideo secundum divisionem materiae sunt multae animae unius speciei, multi autem Angeli unius speciei omnino esse non possunt.

Ad 2

Ad secundum dicendum quod unumquodque hoc modo habet unitatem, quo habet esse, et per consequens idem est iudicium de multiplicatione rei, et de esse ipsius. Manifestum est autem quod anima intellectualis, secundum suum esse, unitur corpori ut forma; et tamen, destructo corpore, remanet anima intellectualis in suo esse. Et eadem ratione multitudo animarum est secundum multitudinem corporum; et tamen, destructis corporibus, remanent animae in suo esse multiplicatae.

Ad 3

Ad tertium dicendum quod individuatio intelligentis, aut speciei per quam intelligit, non excludit intelligentiam universalium, alioquin, cum intellectus separati sint quaedam substantiae subsistentes, et per consequens particulares, non possent universalia intelligere. Sed materialitas cognoscentis et speciei per quam cognoscitur, universalis cognitionem impedit.

Sicut enim omnis actio est secundum modum formae qua agens agit, ut calefactio secundum modum caloris; ita cognitio est secundum modum speciei qua cognoscens cognoscit. Manifestum est autem quod natura communis distinguitur et multiplicatur secundum principia individuantia, quae sunt ex parte materiae. Si ergo forma per quam fit cognitio, sit materialis, non abstracta a conditionibus materiae, erit similitudo naturae speciei aut generis, secundum quod est distincta et multiplicata per principia individuantia, et ita non poterit cognosci natura rei in sua communitate. Si vero species sit abstracta a conditionibus materiae individualis, erit similitudo naturae absque iis quae ipsam distinguunt et multiplicant, et ita cognoscetur universale. Nec refert, quantum ad hoc, utrum sit unus intellectus vel plures, quia si etiam esset unus tantum, oporteret ipsum esse aliquem quendam, et speciem per quam intelligit esse aliquam quandam.

Ad 4

Ad quartum dicendum quod, sive intellectus sit unus sive plures, id quod intelligitur est unum. Id enim quod intelligitur non est in intellectu secundum se, sed secundum suam similitudinem, lapis enim non est in anima, sed species lapidis, ut dicitur in III de anima.

Et tamen lapis est id quod intelligitur, non autem species lapidis, nisi per reflexionem intellectus supra seipsum, alioquin scientiae non essent de rebus, sed de speciebus intelligibilibus. Contingit autem eidem rei diversa secundum diversas formas assimilari. Et quia cognitio fit secundum assimilationem cognoscentis ad rem cognitam, sequitur quod idem a diversis cognoscentibus cognosci contingit, ut patet in sensu, nam plures vident eundem colorem, secundum diversas similitudines. Et similiter plures intellectus intelligunt unam rem intellectam. Sed hoc tantum interest inter sensum et intellectum, secundum sententiam Aristotelis, quod res sentitur secundum illam dispositionem quam extra animam habet, in sua particularitate, natura autem rei quae intelligitur, est quidem extra animam, sed non habet illum modum essendi extra animam, secundum quem intelligitur.

Intelligitur enim natura communis seclusis principiis individuantibus; non autem hunc modum essendi habet extra animam.

Sed secundum sententiam Platonis, res intellecta eo modo est extra animam quo intelligitur, posuit enim naturas rerum a materia separatas.

Ad 5

Ad quintum dicendum quod scientia alia est in discipulo, et alia in magistro. Quomodo autem causetur, in sequentibus ostendetur.

Ad 6

Ad sextum dicendum quod Augustinus intelligit animas non esse plures tantum, quin uniantur in una ratione speciei.