Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that in man there is another form besides the intellectual soul. For the Philosopher says (De Anima ii, 1), that "the soul is the act of a physical body which has life potentially." Therefore the soul is to the body as a form of matter. But the body has a substantial form by which it is a body. Therefore some other substantial form in the body precedes the soul.

Objection 2: Further, man moves himself as every animal does. Now everything that moves itself is divided into two parts, of which one moves, and the other is moved, as the Philosopher proves (Phys. viii, 5). But the part which moves is the soul. Therefore the other part must be such that it can be moved. But primary matter cannot be moved (Phys. v, 1), since it is a being only potentially; indeed everything that is moved is a body. Therefore in man and in every animal there must be another substantial form, by which the body is constituted.

Objection 3: Further, the order of forms depends on their relation to primary matter; for "before" and "after" apply by comparison to some beginning. Therefore if there were not in man some other substantial form besides the rational soul, and if this were to inhere immediately to primary matter; it would follow that it ranks among the most imperfect forms which inhere to matter immediately.

Objection 4: Further, the human body is a mixed body. Now mingling does not result from matter alone; for then we should have mere corruption. Therefore the forms of the elements must remain in a mixed body; and these are substantial forms. Therefore in the human body there are other substantial forms besides the intellectual soul.

On the contrary, Of one thing there is but one substantial being. But the substantial form gives substantial being. Therefore of one thing there is but one substantial form. But the soul is the substantial form of man. Therefore it is impossible for there to be in man another substantial form besides the intellectual soul.

I answer that, If we suppose that the intellectual soul is not united to the body as its form, but only as its motor, as the Platonists maintain, it would necessarily follow that in man there is another substantial form, by which the body is established in its being as movable by the soul. If, however, the intellectual soul be united to the body as its substantial form, as we have said above (Article 1), it is impossible for another substantial form besides the intellectual soul to be found in man.

In order to make this evident, we must consider that the substantial form differs from the accidental form in this, that the accidental form does not make a thing to be "simply," but to be "such," as heat does not make a thing to be simply, but only to be hot. Therefore by the coming of the accidental form a thing is not said to be made or generated simply, but to be made such, or to be in some particular condition; and in like manner, when an accidental form is removed, a thing is said to be corrupted, not simply, but relatively. Now the substantial form gives being simply; therefore by its coming a thing is said to be generated simply; and by its removal to be corrupted simply. For this reason, the old natural philosophers, who held that primary matter was some actual being---for instance, fire or air, or something of that sort---maintained that nothing is generated simply, or corrupted simply; and stated that "every becoming is nothing but an alteration," as we read, Phys. i, 4. Therefore, if besides the intellectual soul there pre-existed in matter another substantial form by which the subject of the soul were made an actual being, it would follow that the soul does not give being simply; and consequently that it is not the substantial form: and so at the advent of the soul there would not be simple generation; nor at its removal simple corruption, all of which is clearly false.

Whence we must conclude, that there is no other substantial form in man besides the intellectual soul; and that the soul, as it virtually contains the sensitive and nutritive souls, so does it virtually contain all inferior forms, and itself alone does whatever the imperfect forms do in other things. The same is to be said of the sensitive soul in brute animals, and of the nutritive soul in plants, and universally of all more perfect forms with regard to the imperfect.

Reply to Objection 1: Aristotle does not say that the soul is the act of a body only, but "the act of a physical organic body which has life potentially"; and that this potentiality "does not reject the soul." Whence it is clear that when the soul is called the act, the soul itself is included; as when we say that heat is the act of what is hot, and light of what is lucid; not as though lucid and light were two separate things, but because a thing is made lucid by the light. In like manner, the soul is said to be the "act of a body," etc., because by the soul it is a body, and is organic, and has life potentially. Yet the first act is said to be in potentiality to the second act, which is operation; for such a potentiality "does not reject"---that is, does not exclude---the soul.

Reply to Objection 2: The soul does not move the body by its essence, as the form of the body, but by the motive power, the act of which presupposes the body to be already actualized by the soul: so that the soul by its motive power is the part which moves; and the animate body is the part moved.

Reply to Objection 3: We observe in matter various degrees of perfection, as existence, living, sensing, and understanding. Now what is added is always more perfect. Therefore that form which gives matter only the first degree of perfection is the most imperfect; while that form which gives the first, second, and third degree, and so on, is the most perfect: and yet it inheres to matter immediately.

Reply to Objection 4: Avicenna held that the substantial forms of the elements remain entire in the mixed body; and that the mixture is made by the contrary qualities of the elements being reduced to an average. But this is impossible, because the various forms of the elements must necessarily be in various parts of matter; for the distinction of which we must suppose dimensions, without which matter cannot be divisible. Now matter subject to dimension is not to be found except in a body. But various bodies cannot be in the same place. Whence it follows that elements in the mixed body would be distinct as to situation. And then there would not be a real mixture which is in respect of the whole; but only a mixture apparent to sense, by the juxtaposition of particles.

Averroes maintained that the forms of elements, by reason of their imperfection, are a medium between accidental and substantial forms, and so can be "more" or "less"; and therefore in the mixture they are modified and reduced to an average, so that one form emerges from them. But this is even still more impossible. For the substantial being of each thing consists in something indivisible, and every addition and subtraction varies the species, as in numbers, as stated in Metaph. viii (Did. vii, 3); and consequently it is impossible for any substantial form to receive "more" or "less." Nor is it less impossible for anything to be a medium between substance and accident.

Therefore we must say, in accordance with the Philosopher (De Gener. i, 10), that the forms of the elements remain in the mixed body, not actually but virtually. For the proper qualities of the elements remain, though modified; and in them is the power of the elementary forms. This quality of the mixture is the proper disposition for the substantial form of the mixed body; for instance, the form of a stone, or of any sort of soul.

Articulus 4

Argumentum 1

Ad quartum sic proceditur. Videtur quod in homine sit alia forma praeter animam intellectivam.

Dicit enim philosophus, in II de anima, quod anima est actus corporis physici potentia vitam habentis.

Comparatur igitur anima ad corpus, sicut forma ad materiam. Sed corpus habet aliquam formam substantialem per quam est corpus.

Ergo ante animam praecedit in corpore aliqua forma substantialis.

Argumentum 2

Praeterea, homo et quodlibet animal est movens seipsum.

Omne autem movens seipsum dividitur in duas partes, quarum una est movens, et alia est mota, ut probatur in VIII physic..

Pars autem movens est anima.

Ergo oportet quod alia pars sit talis quae possit esse mota.

Sed materia prima non potest moveri, ut dicitur in V physic., cum sit ens solum in potentia, quinimmo omne quod movetur est corpus. Ergo oportet quod in homine et in quolibet animali sit alia forma substantialis, per quam constituatur corpus.

Argumentum 3

Praeterea, ordo in formis attenditur secundum habitudinem ad materiam primam, prius enim et posterius dicitur per comparationem ad aliquod principium. Si ergo non esset in homine alia forma substantialis praeter animam rationalem, sed immediate materiae primae inhaereret; sequeretur quod esset in ordine imperfectissimarum formarum, quae immediate inhaerent materiae.

Argumentum 4

Praeterea, corpus humanum est corpus mixtum. Mixtio autem non fit secundum materiam tantum, quia tunc esset corruptio sola.

Oportet ergo quod remaneant formae elementorum in corpore mixto, quae sunt formae substantiales. Ergo in corpore humano sunt aliae formae substantiales praeter animam intellectivam.

Sed Contra

Sed contra, unius rei est unum esse substantiale. Sed forma substantialis dat esse substantiale. Ergo unius rei est una tantum forma substantialis. Anima autem est forma substantialis hominis. Ergo impossibile est quod in homine sit aliqua alia forma substantialis quam anima intellectiva.

Corpus

Respondeo dicendum quod, si poneretur anima intellectiva non uniri corpori ut forma, sed solum ut motor, ut Platonici posuerunt; necesse esset dicere quod in homine esset alia forma substantialis, per quam corpus ab anima mobile in suo esse constitueretur.

Sed si anima intellectiva unitur corpori ut forma substantialis, sicut supra iam diximus, impossibile est quod aliqua alia forma substantialis praeter eam inveniatur in homine. Ad cuius evidentiam, considerandum est quod forma substantialis in hoc a forma accidentali differt quia forma accidentalis non dat esse simpliciter, sed esse tale, sicut calor facit suum subiectum non simpliciter esse, sed esse calidum.

Et ideo cum advenit forma accidentalis, non dicitur aliquid fieri vel generari simpliciter, sed fieri tale aut aliquo modo se habens, et similiter cum recedit forma accidentalis, non dicitur aliquid corrumpi simpliciter, sed secundum quid. Forma autem substantialis dat esse simpliciter, et ideo per eius adventum dicitur aliquid simpliciter generari, et per eius recessum simpliciter corrumpi.

Et propter hoc antiqui naturales, qui posuerunt materiam primam esse aliquod ens actu, puta ignem aut aerem aut aliquid huiusmodi, dixerunt quod nihil generatur aut corrumpitur simpliciter, sed omne fieri statuerunt alterari, ut dicitur in I physic..

Si igitur ita esset, quod praeter animam intellectivam praeexisteret quaecumque alia forma substantialis in materia, per quam subiectum animae esset ens actu; sequeretur quod anima non daret esse simpliciter; et per consequens quod non esset forma substantialis; et quod per adventum animae non esset generatio simpliciter, neque per eius abscessum corruptio simpliciter, sed solum secundum quid. Quae sunt manifeste falsa.

Unde dicendum est quod nulla alia forma substantialis est in homine, nisi sola anima intellectiva; et quod ipsa, sicut virtute continet animam sensitivam et nutritivam, ita virtute continet omnes inferiores formas, et facit ipsa sola quidquid imperfectiores formae in aliis faciunt. Et similiter est dicendum de anima sensitiva in brutis, et de nutritiva in plantis, et universaliter de omnibus formis perfectioribus respectu imperfectiorum.

Ad 1

Ad primum ergo dicendum quod Aristoteles non dicit animam esse actum corporis tantum, sed actum corporis physici organici potentia vitam habentis, et quod talis potentia non abiicit animam.

Unde manifestum est quod in eo cuius anima dicitur actus, etiam anima includitur; eo modo loquendi quo dicitur quod calor est actus calidi, et lumen est actus lucidi; non quod seorsum sit lucidum sine luce, sed quia est lucidum per lucem.

Et similiter dicitur quod anima est actus corporis etc., quia per animam et est corpus, et est organicum, et est potentia vitam habens. Sed actus primus dicitur in potentia respectu actus secundi, qui est operatio.

Talis enim potentia est non abiiciens, idest non excludens, animam.

Ad 2

Ad secundum dicendum quod anima non movet corpus per esse suum, secundum quod unitur corpori ut forma; sed per potentiam motivam, cuius actus praesupponit iam corpus effectum in actu per animam; ut sic anima secundum vim motivam sit pars movens, et corpus animatum sit pars mota.

Ad 3

Ad tertium dicendum quod in materia considerantur diversi gradus perfectionis, sicut esse, vivere sentire et intelligere.

Semper autem secundum superveniens priori, perfectius est.

Forma ergo quae dat solum primum gradum perfectionis materiae, est imperfectissima, sed forma quae dat primum et secundum, et tertium, et sic deinceps, est perfectissima; et tamen materiae immediata.

Ad 4

Ad quartum dicendum quod Avicenna posuit formas substantiales elementorum integras remanere in mixto, mixtionem autem fieri secundum quod contrariae qualitates elementorum reducuntur ad medium.

Sed hoc est impossibile. Quia diversae formae elementorum non possunt esse nisi in diversis partibus materiae; ad quarum diversitatem oportet intelligi dimensiones, sine quibus materia divisibilis esse non potest. Materia autem dimensioni subiecta non invenitur nisi in corpore. Diversa autem corpora non possunt esse in eodem loco. Unde sequitur quod elementa sint in mixto distincta secundum situm. Et ita non erit vera mixtio, quae est secundum totum, sed mixtio ad sensum, quae est secundum minima iuxta se posita.

Averroes autem posuit, in III de caelo, quod formae elementorum, propter sui imperfectionem, sunt mediae inter formas accidentales et substantiales; et ideo recipiunt magis et minus; et ideo remittuntur in mixtione et ad medium reducuntur, et conflatur ex eis una forma.

Sed hoc est etiam magis impossibile. Nam esse substantiale cuiuslibet rei in indivisibili consistit; et omnis additio et subtractio variat speciem, sicut in numeris, ut dicitur in VIII metaphys..

Unde impossibile est quod forma substantialis quaecumque recipiat magis et minus.

Nec minus est impossibile aliquid esse medium inter substantiam et accidens. Et ideo dicendum est, secundum philosophum in I de generat., quod formae elementorum manent in mixto non actu, sed virtute.

Manent enim qualitates propriae elementorum, licet remissae, in quibus est virtus formarum elementarium. Et huiusmodi qualitas mixtionis est propria dispositio ad formam substantialem corporis mixti, puta formam lapidis, vel animae cuiuscumque.