Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that the essence of the soul is its power. For Augustine says (De Trin. ix, 4), that "mind, knowledge, and love are in the soul substantially, or, which is the same thing, essentially": and (De Trin. x, 11), that "memory, understanding, and will are one life, one mind, one essence."

Objection 2: Further, the soul is nobler than primary matter. But primary matter is its own potentiality. Much more therefore is the soul its own power.

Objection 3: Further, the substantial form is simpler than the accidental form; a sign of which is that the substantial form is not intensified or relaxed, but is indivisible. But the accidental form is its own power. Much more therefore is that substantial form which is the soul.

Objection 4: Further, we sense by the sensitive power and we understand by the intellectual power. But "that by which we first sense and understand" is the soul, according to the Philosopher (De Anima ii, 2). Therefore the soul is its own power.

Objection 5: Further, whatever does not belong to the essence is an accident. Therefore if the power of the soul is something else besides the essence thereof, it is an accident, which is contrary to Augustine, who says that the foregoing "are not in the soul as in a subject as color or shape, or any other quality, or quantity, are in a body; for whatever is so, does not exceed the subject in which it is: Whereas the mind can love and know other things" (De Trin. ix, 4).

Objection 6: Further, " a simple form cannot be a subject." But the soul is a simple form; since it is not composed of matter and form, as we have said above (Question 75, Article 5). Therefore the power of the soul cannot be in it as in a subject.

Objection 7: Further, an accident is not the principle of a substantial difference. But sensitive and rational are substantial differences; and they are taken from sense and reason, which are powers of the soul. Therefore the powers of the soul are not accidents; and so it would seem that the power of the soul is its own essence.

On the contrary, Dionysius (Coel. Hier. xi) says that "heavenly spirits are divided into essence, power, and operation." Much more, then, in the soul is the essence distinct from the virtue or power.

I answer that, It is impossible to admit that the power of the soul is its essence, although some have maintained it. For the present purpose this may be proved in two ways. First, because, since power and act divide being and every kind of being, we must refer a power and its act to the same genus. Therefore, if the act be not in the genus of substance, the power directed to that act cannot be in the genus of substance. Now the operation of the soul is not in the genus of substance; for this belongs to God alone, whose operation is His own substance. Wherefore the Divine power which is the principle of His operation is the Divine Essence itself. This cannot be true either of the soul, or of any creature; as we have said above when speaking of the angels (Question 54, Article 3). Secondly, this may be also shown to be impossible in the soul. For the soul by its very essence is an act. Therefore if the very essence of the soul were the immediate principle of operation, whatever has a soul would always have actual vital actions, as that which has a soul is always an actually living thing. For as a form the soul is not an act ordained to a further act, but the ultimate term of generation. Wherefore, for it to be in potentiality to another act, does not belong to it according to its essence, as a form, but according to its power. So the soul itself, as the subject of its power, is called the first act, with a further relation to the second act. Now we observe that what has a soul is not always actual with respect to its vital operations; whence also it is said in the definition of the soul, that it is "the act of a body having life potentially"; which potentiality, however, "does not exclude the soul." Therefore it follows that the essence of the soul is not its power. For nothing is in potentiality by reason of an act, as act.

Reply to Objection 1: Augustine is speaking of the mind as it knows and loves itself. Thus knowledge and love as referred to the soul as known and loved, are substantially or essentially in the soul, for the very substance or essence of the soul is known and loved. In the same way are we to understand what he says in the other passage, that those things are "one life, one mind, one essence." Or, as some say, this passage is true in the sense in which the potential whole is predicated of its parts, being midway between the universal whole, and the integral whole. For the universal whole is in each part according to its entire essence and power; as animal in a man and in a horse; and therefore it is properly predicated of each part. But the integral whole is not in each part, neither according to its whole essence, nor according to its whole power. Therefore in no way can it be predicated of each part; yet in a way it is predicated, though improperly, of all the parts together; as if we were to say that the wall, roof, and foundations are a house. But the potential whole is in each part according to its whole essence, not, however, according to its whole power. Therefore in a way it can be predicated of each part, but not so properly as the universal whole. In this sense, Augustine says that the memory, understanding, and the will are the one essence of the soul.

Reply to Objection 2: The act to which primary matter is in potentiality is the substantial form. Therefore the potentiality of matter is nothing else but its essence.

Reply to Objection 3: Action belongs to the composite, as does existence; for to act belongs to what exists. Now the composite has substantial existence through the substantial form; and it operates by the power which results from the substantial form. Hence an active accidental form is to the substantial form of the agent (for instance, heat compared to the form of fire) as the power of the soul is to the soul.

Reply to Objection 4: That the accidental form is a principle of action is due to the substantial form. Therefore the substantial form is the first principle of action; but not the proximate principle. In this sense the Philosopher says that "the soul is that whereby we understand and sense."

Reply to Objection 5: If we take accident as meaning what is divided against substance, then there can be no medium between substance and accident; because they are divided by affirmation and negation, that is, according to existence in a subject, and non-existence in a subject. In this sense, as the power of the soul is not its essence, it must be an accident; and it belongs to the second species of accident, that of quality. But if we take accident as one of the five universals, in this sense there is a medium between substance and accident. For the substance is all that belongs to the essence of a thing; whereas whatever is beyond the essence of a thing cannot be called accident in this sense; but only what is not caused by the essential principle of the species. For the 'proper' does not belong to the essence of a thing, but is caused by the essential principles of the species; wherefore it is a medium between the essence and accident thus understood. In this sense the powers of the soul may be said to be a medium between substance and accident, as being natural properties of the soul. When Augustine says that knowledge and love are not in the soul as accidents in a subject, this must be understood in the sense given above, inasmuch as they are compared to the soul, not as loving and knowing, but as loved and known. His argument proceeds in this sense; for if love were in the soul loved as in a subject, it would follow that an accident transcends its subject, since even other things are loved through the soul.

Reply to Objection 6: Although the soul is not composed of matter and form, yet it has an admixture of potentiality, as we have said above (Question 75, Article 5, ad 4); and for this reason it can be the subject of an accident. The statement quoted is verified in God, Who is the Pure Act; in treating of which subject Boethius employs that phrase (De Trin. i).

Reply to Objection 7: Rational and sensitive, as differences, are not taken from the powers of sense and reason, but from the sensitive and rational soul itself. But because substantial forms, which in themselves are unknown to us, are known by their accidents; nothing prevents us from sometimes substituting accidents for substantial differences.

Articulus 1

Argumentum 1

Ad primum sic proceditur. Videtur quod ipsa essentia animae sit eius potentia.

Dicit enim Augustinus, in IX de Trin., quod mens, notitia et amor sunt substantialiter in anima, vel, ut idem dicam, essentialiter.

Et in X dicit quod memoria, intelligentia et voluntas sunt una vita, una mens, una essentia.

Argumentum 2

Praeterea, anima est nobilior quam materia prima. Sed materia prima est sua potentia. Ergo multo magis anima.

Argumentum 3

Praeterea, forma substantialis est simplicior quam accidentalis, cuius signum est, quod forma substantialis non intenditur vel remittitur, sed in indivisibili consistit. Forma autem accidentalis est ipsa sua virtus.

Ergo multo magis forma substantialis, quae est anima.

Argumentum 4

Praeterea, potentia sensitiva est qua sentimus, et potentia intellectiva qua intelligimus. Sed id quo primo sentimus et intelligimus est anima, secundum philosophum, in II de anima.

Ergo anima est suae potentiae.

Argumentum 5

Praeterea, omne quod non est de essentia rei, est accidens.

Si ergo potentia animae est praeter essentiam eius, sequitur quod sit accidens. Quod est contra Augustinum, in IX de Trin., ubi dicit quod praedicta non sunt in anima sicut in subiecto, ut color aut figura in corpore, aut ulla alia qualitas aut quantitas, quidquid enim tale est, non excedit subiectum in quo est; mens autem potest etiam alia amare et cognoscere.

Argumentum 6

Praeterea, forma simplex subiectum esse non potest.

Anima autem est forma simplex, cum non sit composita ex materia et forma, ut supra dictum est.

Non ergo potentia animae potest esse in ipsa sicut in subiecto.

Argumentum 7

Praeterea, accidens non est principium substantialis differentiae.

Sed sensibile et rationale sunt substantiales differentiae, et sumuntur a sensu et ratione, quae sunt potentiae animae.

Ergo potentiae animae non sunt accidentia. Et ita videtur quod potentia animae sit eius essentia.

Sed Contra

Sed contra est quod dionysius dicit, XI cap. Caelest. Hier., quod caelestes spiritus dividuntur in essentiam, virtutem et operationem.

Multo igitur magis in anima aliud est essentia, et aliud virtus sive potentia.

Corpus

Respondeo dicendum quod impossibile est dicere quod essentia animae sit eius potentia; licet hoc quidam posuerint.

Et hoc dupliciter ostenditur, quantum ad praesens. Primo quia, cum potentia et actus dividant ens et quodlibet genus entis, oportet quod ad idem genus referatur potentia et actus. Et ideo, si actus non est in genere substantiae, potentia quae dicitur ad illum actum, non potest esse in genere substantiae. Operatio autem animae non est in genere substantiae; sed in solo deo, cuius operatio est eius substantia. Unde dei potentia, quae est operationis principium, est ipsa dei essentia. Quod non potest esse verum neque in anima, neque in aliqua creatura; ut supra etiam de Angelo dictum est.

Secundo, hoc etiam impossibile apparet in anima. Nam anima secundum suam essentiam est actus. Si ergo ipsa essentia animae esset immediatum operationis principium, semper habens animam actu haberet opera vitae; sicut semper habens animam actu est vivum.

Non enim, inquantum est forma, est actus ordinatus ad ulteriorem actum, sed est ultimus terminus generationis. Unde quod sit in potentia adhuc ad alium actum, hoc non competit ei secundum suam essentiam, inquantum est forma; sed secundum suam potentiam.

Et sic ipsa anima, secundum quod subest suae potentiae, dicitur actus primus, ordinatus ad actum secundum. Invenitur autem habens animam non semper esse in actu operum vitae. Unde etiam in definitione animae dicitur quod est actus corporis potentia vitam habentis, quae tamen potentia non abiicit animam. Relinquitur ergo quod essentia animae non est eius potentia. Nihil enim est in potentia secundum actum, inquantum est actus.

Ad 1

Ad primum ergo dicendum quod Augustinus loquitur de mente secundum quod noscit se et amat se.

Sic ergo notitia et amor, inquantum referuntur ad ipsam ut cognitam et amatam, substantialiter vel essentialiter sunt in anima, quia ipsa substantia vel essentia animae cognoscitur et amatur.

Et similiter intelligendum est quod alibi dicit, quod sunt una vita, una mens, una essentia.

Vel, sicut quidam dicunt, haec locutio verificatur secundum modum quo totum potestativum praedicatur de suis partibus, quod medium est inter totum universale et totum integrale.

Totum enim universale adest cuilibet parti secundum totam suam essentiam et virtutem, ut animal homini et equo, et ideo proprie de singulis partibus praedicatur. Totum vero integrale non est in qualibet parte, neque secundum totam essentiam, neque secundum totam virtutem. Et ideo nullo modo de singulis partibus praedicatur; sed aliquo modo, licet improprie, praedicatur de omnibus simul, ut si dicamus quod paries, tectum et fundamentum sunt domus. Totum vero potentiale adest singulis partibus secundum totam suam essentiam, sed non secundum totam virtutem.

Et ideo quodammodo potest praedicari de qualibet parte; sed non ita proprie sicut totum universale.

Et per hunc modum Augustinus dicit quod memoria, intelligentia et voluntas sunt una animae essentia.

Ad 2

Ad secundum dicendum quod actus ad quem est in potentia materia prima, est substantialis forma. Et ideo potentia materiae non est aliud quam eius essentia.

Ad 3

Ad tertium dicendum quod actio est compositi, sicut et esse, existentis enim est agere. Compositum autem per formam substantialem habet esse substantialiter; per virtutem autem quae consequitur formam substantialem, operatur. Unde sic se habet forma accidentalis activa ad formam substantialem agentis (ut calor ad formam ignis), sicut se habet potentia animae ad animam.

Ad 4

Ad quartum dicendum quod hoc ipsum quod forma accidentalis est actionis principium, habet a forma substantiali. Et ideo forma substantialis est primum actionis principium, sed non proximum.

Et secundum hoc philosophus dicit quod id quo intelligimus et sentimus, est anima.

Ad 5

Ad quintum dicendum quod, si accidens accipiatur secundum quod dividitur contra substantiam, sic nihil potest esse medium inter substantiam et accidens, quia dividuntur secundum affirmationem et negationem, scilicet secundum esse in subiecto et non esse in subiecto. Et hoc modo, cum potentia animae non sit eius essentia, oportet quod sit accidens, et est in secunda specie qualitatis.

Si vero accipiatur accidens secundum quod ponitur unum quinque universalium, sic aliquid est medium inter substantiam et accidens. Quia ad substantiam pertinet quidquid est essentiale rei, non autem quidquid est extra essentiam, potest sic dici accidens, sed solum id quod non causatur ex principiis essentialibus speciei. Proprium enim non est de essentia rei, sed ex principiis essentialibus speciei causatur, unde medium est inter essentiam et accidens sic dictum. Et hoc modo potentiae animae possunt dici mediae inter substantiam et accidens, quasi proprietates animae naturales.

Quod autem Augustinus dicit, quod notitia et amor non sunt in anima sicut accidentia in subiecto, intelligitur secundum modum praedictum, prout comparantur ad animam, non sicut ad amantem et cognoscentem; sed prout comparantur ad eam sicut ad amatam et cognitam.

Et hoc modo procedit sua probatio, quia si amor esset in anima amata sicut in subiecto, sequeretur quod accidens transcenderet suum subiectum; cum etiam alia sint amata per animam.

Ad 6

Ad sextum dicendum quod anima, licet non sit composita ex materia et forma, habet tamen aliquid de potentialitate admixtum ut supra dictum est.

Et ideo potest esse subiectum accidentis. Propositio autem inducta locum habet in deo, qui est actus purus, in qua materia boetius eam introducit.

Ad 7

Ad septimum dicendum quod rationale et sensibile, prout sunt differentiae, non sumuntur a potentiis sensus et rationis; sed ab ipsa anima sensitiva et rationali. Quia tamen formae substantiales, quae secundum se sunt nobis ignotae, innotescunt per accidentia; nihil prohibet interdum accidentia loco differentiarum substantialium poni.