Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that the intellect can actually understand through the intelligible species of which it is possessed, without turning to the phantasms. For the intellect is made actual by the intelligible species by which it is informed. But if the intellect is in act, it understands. Therefore the intelligible species suffices for the intellect to understand actually, without turning to the phantasms.

Objection 2: Further, the imagination is more dependent on the senses than the intellect on the imagination. But the imagination can actually imagine in the absence of the sensible. Therefore much more can the intellect understand without turning to the phantasms.

Objection 3: There are no phantasms of incorporeal things: for the imagination does not transcend time and space. If, therefore, our intellect cannot understand anything actually without turning to the phantasms, it follows that it cannot understand anything incorporeal. Which is clearly false: for we understand truth, and God, and the angels.

On the contrary, The Philosopher says (De Anima iii, 7) that "the soul understands nothing without a phantasm."

I answer that, In the present state of life in which the soul is united to a passible body, it is impossible for our intellect to understand anything actually, except by turning to the phantasms. First of all because the intellect, being a power that does not make use of a corporeal organ, would in no way be hindered in its act through the lesion of a corporeal organ, if for its act there were not required the act of some power that does make use of a corporeal organ. Now sense, imagination and the other powers belonging to the sensitive part, make use of a corporeal organ. Wherefore it is clear that for the intellect to understand actually, not only when it acquires fresh knowledge, but also when it applies knowledge already acquired, there is need for the act of the imagination and of the other powers. For when the act of the imagination is hindered by a lesion of the corporeal organ, for instance in a case of frenzy; or when the act of the memory is hindered, as in the case of lethargy, we see that a man is hindered from actually understanding things of which he had a previous knowledge. Secondly, anyone can experience this of himself, that when he tries to understand something, he forms certain phantasms to serve him by way of examples, in which as it were he examines what he is desirous of understanding. For this reason it is that when we wish to help someone to understand something, we lay examples before him, from which he forms phantasms for the purpose of understanding.

Now the reason of this is that the power of knowledge is proportioned to the thing known. Wherefore the proper object of the angelic intellect, which is entirely separate from a body, is an intelligible substance separate from a body. Whereas the proper object of the human intellect, which is united to a body, is a quiddity or nature existing in corporeal matter; and through such natures of visible things it rises to a certain knowledge of things invisible. Now it belongs to such a nature to exist in an individual, and this cannot be apart from corporeal matter: for instance, it belongs to the nature of a stone to be in an individual stone, and to the nature of a horse to be in an individual horse, and so forth. Wherefore the nature of a stone or any material thing cannot be known completely and truly, except in as much as it is known as existing in the individual. Now we apprehend the individual through the senses and the imagination. And, therefore, for the intellect to understand actually its proper object, it must of necessity turn to the phantasms in order to perceive the universal nature existing in the individual. But if the proper object of our intellect were a separate form; or if, as the Platonists say, the natures of sensible things subsisted apart from the individual; there would be no need for the intellect to turn to the phantasms whenever it understands.

Reply to Objection 1: The species preserved in the passive intellect exist there habitually when it does not understand them actually, as we have said above (Question 79, Article 6). Wherefore for us to understand actually, the fact that the species are preserved does not suffice; we need further to make use of them in a manner befitting the things of which they are the species, which things are natures existing in individuals.

Reply to Objection 2: Even the phantasm is the likeness of an individual thing; wherefore the imagination does not need any further likeness of the individual, whereas the intellect does.

Reply to Objection 3: Incorporeal things, of which there are no phantasms, are known to us by comparison with sensible bodies of which there are phantasms. Thus we understand truth by considering a thing of which we possess the truth; and God, as Dionysius says (Div. Nom. i), we know as cause, by way of excess and by way of remotion. Other incorporeal substances we know, in the present state of life, only by way of remotion or by some comparison to corporeal things. And, therefore, when we understand something about these things, we need to turn to phantasms of bodies, although there are no phantasms of the things themselves.

Articulus 7

Argumentum 1

Ad septimum sic proceditur. Videtur quod intellectus possit actu intelligere per species intelligibiles quas penes se habet, non convertendo se ad phantasmata. Intellectus enim fit in actu per speciem intelligibilem qua informatur. Sed intellectum esse in actu, est ipsum intelligere. Ergo species intelligibiles sufficiunt ad hoc quod intellectus actu intelligat, absque hoc quod ad phantasmata se convertat.

Argumentum 2

Praeterea, magis dependet imaginatio a sensu, quam intellectus ab imaginatione. Sed imaginatio potest imaginari actu, absentibus sensibilibus. Ergo multo magis intellectus potest intelligere actu, non convertendo se ad phantasmata.

Argumentum 3

Praeterea, incorporalium non sunt aliqua phantasmata, quia imaginatio tempus et continuum non transcendit. Si ergo intellectus noster non posset aliquid intelligere in actu nisi converteretur ad phantasmata, sequeretur quod non posset intelligere incorporeum aliquid. Quod patet esse falsum, intelligimus enim veritatem ipsam, et deum et Angelos.

Sed Contra

Sed contra est quod philosophus dicit, in III de anima, quod nihil sine phantasmate intelligit anima.

Corpus

Respondeo dicendum quod impossibile est intellectum nostrum, secundum praesentis vitae statum, quo passibili corpori coniungitur, aliquid intelligere in actu, nisi convertendo se ad phantasmata. Et hoc duobus indiciis apparet. Primo quidem quia, cum intellectus sit vis quaedam non utens corporali organo, nullo modo impediretur in suo actu per laesionem alicuius corporalis organi, si non requireretur ad eius actum actus alicuius potentiae utentis organo corporali. Utuntur autem organo corporali sensus et imaginatio et aliae vires pertinentes ad partem sensitivam.

Unde manifestum est quod ad hoc quod intellectus actu intelligat, non solum accipiendo scientiam de novo, sed etiam utendo scientia iam acquisita, requiritur actus imaginationis et ceterarum virtutum. Videmus enim quod, impedito actu virtutis imaginativae per laesionem organi, ut in phreneticis; et similiter impedito actu memorativae virtutis, ut in lethargicis; impeditur homo ab intelligendo in actu etiam ea quorum scientiam praeaccepit.

Secundo, quia hoc quilibet in seipso experiri potest, quod quando aliquis conatur aliquid intelligere, format aliqua phantasmata sibi per modum exemplorum, in quibus quasi inspiciat quod intelligere studet. Et inde est etiam quod quando alium volumus facere aliquid intelligere, proponimus ei exempla, ex quibus sibi phantasmata formare possit ad intelligendum.

Huius autem ratio est, quia potentia cognoscitiva proportionatur cognoscibili. Unde intellectus angelici, qui est totaliter a corpore separatus, obiectum proprium est substantia intelligibilis a corpore separata; et per huiusmodi intelligibilia materialia cognoscit. Intellectus autem humani, qui est coniunctus corpori, proprium obiectum est quidditas sive natura in materia corporali existens; et per huiusmodi naturas visibilium rerum etiam in invisibilium rerum aliqualem cognitionem ascendit.

De ratione autem huius naturae est, quod in aliquo individuo existat, quod non est absque materia corporali, sicut de ratione naturae lapidis est quod sit in hoc lapide, et de ratione naturae equi quod sit in hoc equo, et sic de aliis. Unde natura lapidis, vel cuiuscumque materialis rei, cognosci non potest complete et vere, nisi secundum quod cognoscitur ut in particulari existens. Particulare autem apprehendimus per sensum et imaginationem. Et ideo necesse est ad hoc quod intellectus actu intelligat suum obiectum proprium, quod convertat se ad phantasmata, ut speculetur naturam universalem in particulari existentem. Si autem proprium obiectum intellectus nostri esset forma separata; vel si naturae rerum sensibilium subsisterent non in particularibus, secundum Platonicos; non oporteret quod intellectus noster semper intelligendo converteret se ad phantasmata.

Ad 1

Ad primum ergo dicendum quod species conservatae in intellectu possibili, in eo existunt habitualiter quando actu non intelligit, sicut supra dictum est.

Unde ad hoc quod intelligamus in actu, non sufficit ipsa conservatio specierum; sed oportet quod eis utamur secundum quod convenit rebus quarum sunt species, quae sunt naturae in particularibus existentes.

Ad 2

Ad secundum dicendum quod etiam ipsum phantasma est similitudo rei particularis, unde non indiget imaginatio aliqua alia similitudine particularis, sicut indiget intellectus.

Ad 3

Ad tertium dicendum quod incorporea, quorum non sunt phantasmata, cognoscuntur a nobis per comparationem ad corpora sensibilia, quorum sunt phantasmata. Sicut veritatem intelligimus ex consideratione rei circa quam veritatem speculamur; deum autem, ut dionysius dicit, cognoscimus ut causam, et per excessum, et per remotionem; alias etiam incorporeas substantias, in statu praesentis vitae, cognoscere non possumus nisi per remotionem, vel aliquam comparationem ad corporalia. Et ideo cum de huiusmodi aliquid intelligimus, necesse habemus converti ad phantasmata corporum, licet ipsorum non sint phantasmata.