1 Objection 1: It would seem that the intellect is not a power of the soul, but the essence of the soul. For the intellect seems to be the same as the mind. Now the mind is not a power of the soul, but the essence; for Augustine says De Trin. ix, 2): Mind and spirit are not relative things, but denominate the essence. Therefore the intellect is the essence of the soul.
1 Ad primum sic proceditur. Videtur quod intellectus non sit aliqua potentia animae, sed sit ipsa eius essentia. Intellectus idem enim videtur esse quod mens. Sed mens non est potentia animae sed essentia, dicit enim Augustinus, IX de Trin., mens et spiritus non relative dicuntur, sed essentiam demonstrant. Ergo intellectus est ipsa essentia animae.
2 Objection 2: Further, different genera of the soul's powers are not united in some one power, but only in the essence of the soul. Now the appetitive and the intellectual are different genera of the soul's powers as the Philosopher says De Anima ii, 3), but they are united in the mind, for Augustine De Trin. x, 11) places the intelligence and will in the mind. Therefore the mind and intellect of man is of the very essence of the soul and not a power thereof.
2 Praeterea, diversa genera potentiarum animae non uniuntur in aliqua potentia una, sed in sola essentia animae. Appetitivum autem et intellectivum sunt diversa genera potentiarum animae, ut dicitur in II de anima; conveniunt autem in mente, quia Augustinus, X de Trin., ponit intelligentiam et voluntatem in mente. Ergo mens et intellectus est ipsa essentia animae, et non aliqua eius potentia.
3 Objection 3: Further, according to Gregory, in a homily for the Ascension xxix in Ev.), man understands with the angels. But angels are called minds and intellects. Therefore the mind and intellect of man are not a power of the soul, but the soul itself.
3 Praeterea, secundum Gregorium, in homilia ascensionis, homo intelligit cum Angelis. Sed Angeli dicuntur mentes et intellectus. Ergo mens et intellectus hominis non est aliqua potentia animae, sed ipsa anima.
4 Objection 4: Further, a substance is intellectual by the fact that it is immaterial. But the soul is immaterial through its essence. Therefore it seems that the soul must be intellectual through its essence.
4 Praeterea, ex hoc convenit alicui substantiae quod sit intellectiva, quia est immaterialis. Sed anima est immaterialis per suam essentiam. Ergo videtur quod anima per suam essentiam sit intellectiva.
5 On the contrary, The Philosopher assigns the intellectual faculty as a power of the soul De Anima ii, 3).
5 Sed contra est quod philosophus ponit intellectivum potentiam animae, ut patet in II de anima.
6 I answer that, In accordance with what has been already shown Question 54, Article 3; Question 77, Article 1) it is necessary to say that the intellect is a power of the soul, and not the very essence of the soul. For then alone the essence of that which operates is the immediate principle of operation, when operation itself is its being: for as power is to operation as its act, so is the essence to being. But in God alone His action of understanding is His very Being. Wherefore in God alone is His intellect His essence: while in other intellectual creatures, the intellect is power.
6 Respondeo dicendum quod necesse est dicere, secundum praemissa, quod intellectus sit aliqua potentia animae, et non ipsa animae essentia. Tunc enim solum immediatum principium operationis est ipsa essentia rei operantis, quando ipsa operatio est eius esse, sicut enim potentia se habet ad operationem ut ad suum actum, ita se habet essentia ad esse. In solo Deo autem idem est intelligere quod suum esse. Unde in solo Deo intellectus est eius essentia, in aliis autem creaturis intellectualibus intellectus est quaedam potentia intelligentis.
7 Reply to Objection 1: Sense is sometimes taken for the power, and sometimes for the sensitive soul; for the sensitive soul takes its name from its chief power, which is sense. And in like manner the intellectual soul is sometimes called intellect, as from its chief power; and thus we read De Anima i, 4), that the intellect is a substance. And in this sense also Augustine says that the mind is spirit and essence De Trin. ix, 2; xiv, 16).
7 Ad primum ergo dicendum quod sensus accipitur aliquando pro potentia, aliquando vero pro ipsa anima sensitiva, denominatur enim anima sensitiva nomine principalioris suae potentiae, quae est sensus. Et similiter anima intellectiva quandoque nominatur nomine intellectus, quasi a principaliori sua virtute; sicut dicitur in I de anima, quod intellectus est substantia quaedam. Et etiam hoc modo Augustinus dicit quod mens est spiritus, vel essentia.
8 Reply to Objection 2: The appetitive and intellectual powers are different genera of powers in the soul, by reason of the different formalities of their objects. But the appetitive power agrees partly with the intellectual power and partly with the sensitive in its mode of operation either through a corporeal organ or without it: for appetite follows apprehension. And in this way Augustine puts the will in the mind; and the Philosopher, in the reason De Anima iii, 9).
8 Ad secundum dicendum quod appetitivum et intellectivum sunt diversa genera potentiarum animae, secundum diversas rationes obiectorum. Sed appetitivum partim convenit cum intellectivo, et partim cum sensitivo, quantum ad modum operandi per organum corporale, vel sine huiusmodi organo, nam appetitus sequitur apprehensionem. Et secundum hoc Augustinus ponit voluntatem in mente, et philosophus in ratione.
9 Reply to Objection 3: In the angels there is no other power besides the intellect, and the will, which follows the intellect. And for this reason an angel is called a mind or an intellect; because his whole power consists in this. But the soul has many other powers, such as the sensitive and nutritive powers, and therefore the comparison fails.
9 Ad tertium dicendum quod in Angelis non est alia vis nisi intellectiva, et voluntas, quae ad intellectum consequitur. Et propter hoc Angelus dicitur mens vel intellectus, quia tota virtus sua in hoc consistit. Anima autem habet multas alias vires, sicut sensitivas et nutritivas, et ideo non est simile.
10 Reply to Objection 4: The immateriality of the created intelligent substance is not its intellect; and through its immateriality it has the power of intelligence. Wherefore it follows not that the intellect is the substance of the soul, but that it is its virtue and power.
10 Ad quartum dicendum quod ipsa immaterialitas substantiae intelligentis creatae non est eius intellectus; sed ex immaterialitate habet virtutem ad intelligendum. Unde non oportet quod intellectus sit substantia animae, sed eius virtus et potentia.