Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that there cannot be many habits in one power. For when several things are distinguished in respect of the same thing, if one of them be multiplied, the others are too. Now habits and powers are distinguished in respect of the same thing, viz. their acts and objects. Therefore they are multiplied in like manner. Therefore there cannot be many habits in one power.

Objection 2: Further, a power is a simple force. Now in one simple subject there cannot be diversity of accidents; for the subject is the cause of its accidents; and it does not appear how diverse effects can proceed from one simple cause. Therefore there cannot be many habits in one power.

Objection 3: Further, just as the body is informed by its shape, so is a power informed by a habit. But one body cannot be informed at the same time by various shapes. Therefore neither can a power be informed at the same time by many habits. Therefore several habits cannot be at the same time in one power.

On the contrary, The intellect is one power; wherein, nevertheless, are the habits of various sciences.

I answer that, As stated above (Question 49, Article 4), habits are dispositions of a thing that is in potentiality to something, either to nature, or to operation, which is the end of nature. As to those habits which are dispositions to nature, it is clear that several can be in one same subject: since in one subject we may take parts in various ways, according to the various dispositions of which parts there are various habits. Thus, if we take the humors as being parts of the human body, according to their disposition in respect of human nature, we have the habit or disposition of health: while, if we take like parts, such as nerves, bones, and flesh, the disposition of these in respect of nature is strength or weakness; whereas, if we take the limbs, i.e. the hands, feet, and so on, the disposition of these in proportion to nature, is beauty: and thus there are several habits or dispositions in the same subject.

If, however, we speak of those habits that are dispositions to operation, and belong properly to the powers; thus, again, there may be several habits in one power. The reason for this is that the subject of a habit is a passive power, as stated above (Question 51, Article 2): for it is only an active power that cannot be the subject of a habit, as was clearly shown above (Question 51, Article 2). Now a passive power is compared to the determinate act of any species, as matter to form: because, just as matter is determinate to one form by one agent, so, too, is a passive power determined by the nature of one active object to an act specifically one. Wherefore, just as several objects can move one passive power, so can one passive power be the subject of several acts or perfections specifically diverse. Now habits are qualities or forms adhering to a power, and inclining that power to acts of a determinate species. Consequently several habits, even as several specifically different acts, can belong to one power.

Reply to Objection 1: Even as in natural things, diversity of species is according to the form, and diversity of genus, according to matter, as stated in Metaph. v, text. 33 (since things that differ in matter belong to different genera): so, too, generic diversity of objects entails a difference of powers (wherefore the Philosopher says in Ethic. vi, 1, that "those objects that differ generically belong to different departments of the soul"); while specific difference of objects entails a specific difference of acts, and consequently of habits also. Now things that differ in genus differ in species, but not vice versa. Wherefore the acts and habits of different powers differ in species: but it does not follow that different habits are in different powers, for several can be in one power. And even as several genera may be included in one genus, and several species be contained in one species; so does it happen that there are several species of habits and powers.

Reply to Objection 2: Although a power is simple as to its essence, it is multiple virtually, inasmuch as it extends to many specifically different acts. Consequently there is nothing to prevent many superficially different habits from being in one power.

Reply to Objection 3: A body is informed by its shape as by its own terminal boundaries: whereas a habit is not the terminal boundary of a power, but the disposition of a power to an act as to its ultimate term. Consequently one same power cannot have several acts at the same time, except in so far as perchance one act is comprised in another; just as neither can a body have several shapes, save in so far as one shape enters into another, as a three-sided in a four-sided figure. For the intellect cannot understand several things at the same time "actually"; and yet it can know several things at the same time "habitually."

Articulus 1

Argumentum 1

Ad primum sic proceditur. Videtur quod non possint esse multi habitus in una potentia. Eorum enim quae secundum idem distinguuntur multiplicato uno, multiplicatur et aliud.

Sed secundum idem potentiae et habitus distinguuntur, scilicet secundum actus et obiecta. Similiter ergo multiplicantur. Non ergo possunt esse multi habitus in una potentia.

Argumentum 2

Praeterea, potentia est virtus quaedam simplex. Sed in uno subiecto simplici non potest esse diversitas accidentium, quia subiectum est causa accidentis; ab uno autem simplici non videtur procedere nisi unum.

Ergo in una potentia non possunt esse multi habitus.

Argumentum 3

Praeterea, sicut corpus formatur per figuram, ita potentia formatur per habitum. Sed unum corpus non potest simul formari diversis figuris. Ergo neque una potentia potest simul formari diversis habitibus. Non ergo plures habitus possunt simul esse in una potentia.

Sed Contra

Sed contra est quod intellectus est una potentia, in qua tamen sunt diversarum scientiarum habitus.

Corpus

Respondeo dicendum quod, sicut supra dictum est, habitus sunt dispositiones quaedam alicuius in potentia existentis ad aliquid, sive ad naturam, sive ad operationem vel finem naturae. Et de illis quidem habitibus qui sunt dispositiones ad naturam, manifestum est quod possunt plures esse in uno subiecto, eo quod unius subiecti possunt diversimode partes accipi, secundum quarum dispositionem habitus dicuntur. Sicut, si accipiantur humani corporis partes humores, prout disponuntur secundum naturam humanam, est habitus vel dispositio sanitatis, si vero accipiantur partes similes ut nervi et ossa et carnes, earum dispositio in ordine ad naturam, est fortitudo aut macies, si vero accipiantur membra, ut manus et pes et huiusmodi, earum dispositio naturae conveniens, est pulchritudo.

Et sic sunt plures habitus vel dispositiones in eodem.

Si vero loquamur de habitibus qui sunt dispositiones ad opera, qui proprie pertinent ad potentias; sic etiam contingit unius potentiae esse habitus plures. Cuius ratio est, quia subiectum habitus est potentia passiva, ut supra dictum est, potentia enim activa tantum non est alicuius habitus subiectum, ut ex supradictis patet.

Potentia autem passiva comparatur ad actum determinatum unius speciei, sicut materia ad formam, eo quod, sicut materia determinatur ad unam formam per unum agens, ita etiam potentia passiva a ratione unius obiecti activi determinatur ad unum actum secundum speciem. Unde sicut plura obiecta possunt movere unam potentiam passivam, ita una potentia passiva potest esse subiectum diversorum actuum vel perfectionum secundum speciem. Habitus autem sunt quaedam qualitates aut formae inhaerentes potentiae, quibus inclinatur potentia ad determinatos actus secundum speciem. Unde ad unam potentiam possunt plures habitus pertinere, sicut et plures actus specie differentes.

Ad 1

Ad primum ergo dicendum quod, sicut in rebus naturalibus diversitas specierum est secundum formam, diversitas autem generum est secundum materiam, ut dicitur in V metaphys. (ea enim sunt diversa genere, quorum est materia diversa), ita etiam diversitas obiectorum secundum genus, facit distinctionem potentiarum (unde philosophus dicit, in VI ethic., quod ad ea quae sunt genere altera, sunt etiam animae particulae aliae); diversitas vero obiectorum secundum speciem, facit diversitatem actuum secundum speciem, et per consequens habituum. Quaecumque autem sunt diversa genere, sunt etiam specie diversa, sed non convertitur. Et ideo diversarum potentiarum sunt diversi actus specie, et diversi habitus, non autem oportet quod diversi habitus sint diversarum potentiarum, sed possunt esse plures unius. Et sicut sunt genera generum, et species specierum; ita etiam contingit esse diversas species habituum et potentiarum.

Ad 2

Ad secundum dicendum quod potentia, etsi sit quidem simplex secundum essentiam, est tamen multiplex virtute, secundum quod ad multos actus specie differentes se extendit. Et ideo nihil prohibet in una potentia esse multos habitus specie differentes.

Ad 3

Ad tertium dicendum quod corpus formatur per figuram sicut per propriam terminationem, habitus autem non est terminatio potentiae, sed est dispositio ad actum sicut ad ultimum terminum. Et ideo non possunt esse unius potentiae simul plures actus, nisi forte secundum quod unus comprehenditur sub alio, sicut nec unius corporis plures figurae, nisi secundum quod una est in alia, sicut trigonum in tetragono. Non enim potest intellectus simul multa actu intelligere.

Potest tamen simul habitu multa scire.