Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that our intellect does not understand by composition and division. For composition and division are only of many; whereas the intellect cannot understand many things at the same time. Therefore it cannot understand by composition and division.

Objection 2: Further, every composition and division implies past, present, or future time. But the intellect abstracts from time, as also from other individual conditions. Therefore the intellect does not understand by composition and division.

Objection 3: Further, the intellect understands things by a process of assimilation to them. But composition and division are not in things, for nothing is in things but what is signified by the predicate and the subject, and which is one and the same, provided that the composition be true, for "man" is truly what "animal" is. Therefore the intellect does not act by composition and division.

On the contrary, Words signify the conceptions of the intellect, as the Philosopher says (Peri Herm. i). But in words we find composition and division, as appears in affirmative and negative propositions. Therefore the intellect acts by composition and division.

I answer that, The human intellect must of necessity understand by composition and division. For since the intellect passes from potentiality to act, it has a likeness to things which are generated, which do not attain to perfection all at once but acquire it by degrees: so likewise the human intellect does not acquire perfect knowledge by the first act of apprehension; but it first apprehends something about its object, such as its quiddity, and this is its first and proper object; and then it understands the properties, accidents, and the various relations of the essence. Thus it necessarily compares one thing with another by composition or division; and from one composition and division it proceeds to another, which is the process of reasoning.

But the angelic and the Divine intellect, like all incorruptible things, have their perfection at once from the beginning. Hence the angelic and the Divine intellect have the entire knowledge of a thing at once and perfectly; and hence also in knowing the quiddity of a thing they know at once whatever we can know by composition, division, and reasoning. Therefore the human intellect knows by composition, division and reasoning. But the Divine intellect and the angelic intellect know, indeed, composition, division, and reasoning, not by the process itself, but by understanding the simple essence.

Reply to Objection 1: Composition and division of the intellect are made by differentiating and comparing. Hence the intellect knows many things by composition and division, as by knowing the difference and comparison of things.

Reply to Objection 2: Although the intellect abstracts from the phantasms, it does not understand actually without turning to the phantasms, as we have said (Article 1; Question 84, Article 7). And forasmuch as it turns to the phantasms, composition and division of the intellect involve time.

Reply to Objection 3: The likeness of a thing is received into the intellect according to the mode of the intellect, not according to the mode of the thing. Wherefore something on the part of the thing corresponds to the composition and division of the intellect; but it does not exist in the same way in the intellect and in the thing. For the proper object of the human intellect is the quiddity of a material thing, which comes under the action of the senses and the imagination. Now in a material thing there is a twofold composition. First, there is the composition of form with matter; and to this corresponds that composition of the intellect whereby the universal whole is predicated of its part: for the genus is derived from common matter, while the difference that completes the species is derived from the form, and the particular from individual matter. The second comparison is of accident with subject: and to this real composition corresponds that composition of the intellect, whereby accident is predicated of subject, as when we say "the man is white." Nevertheless composition of the intellect differs from composition of things; for in the latter the things are diverse, whereas composition of the intellect is a sign of the identity of the components. For the above composition of the intellect does not imply that "man" and "whiteness" are identical, but the assertion, "the man is white," means that "the man is something having whiteness": and the subject, which is a man, is identified with a subject having whiteness. It is the same with the composition of form and matter: for animal signifies that which has a sensitive nature; rational, that which has an intellectual nature; man, that which has both; and Socrates that which has all these things together with individual matter; and according to this kind of identity our intellect predicates the composition of one thing with another.

Articulus 5

Argumentum 1

Ad quintum sic proceditur. Videtur quod intellectus noster non intelligat componendo et dividendo. Compositio enim et divisio non est nisi multorum. Sed intellectus non potest simul multa intelligere. Ergo non potest intelligere componendo et dividendo.

Argumentum 2

Praeterea, omni compositioni et divisioni adiungitur tempus praesens, praeteritum vel futurum. Sed intellectus abstrahit a tempore, sicut etiam ab aliis particularibus conditionibus. Ergo intellectus non intelligit componendo et dividendo.

Argumentum 3

Praeterea, intellectus intelligit per assimilationem ad res.

Sed compositio et divisio nihil est in rebus, nihil enim invenitur in rebus nisi res quae significatur per praedicatum et subiectum, quae est una et eadem si compositio est vera; homo enim est vere id quod est animal.

Ergo intellectus non componit et dividit.

Sed Contra

Sed contra, voces significant conceptiones intellectus, ut dicit philosophus in I periherm..

Sed in vocibus est compositio et divisio; ut patet in propositionibus affirmativis et negativis. Ergo intellectus componit et dividit.

Corpus

Respondeo dicendum quod intellectus humanus necesse habet intelligere componendo et dividendo. Cum enim intellectus humanus exeat de potentia in actum, similitudinem quandam habet cum rebus generabilibus, quae non statim perfectionem suam habent, sed eam successive acquirunt. Et similiter intellectus humanus non statim in prima apprehensione capit perfectam rei cognitionem; sed primo apprehendit aliquid de ipsa, puta quidditatem ipsius rei, quae est primum et proprium obiectum intellectus; et deinde intelligit proprietates et accidentia et habitudines circumstantes rei essentiam. Et secundum hoc, necesse habet unum apprehensum alii componere vel dividere; et ex una compositione vel divisione ad aliam procedere, quod est ratiocinari. Intellectus autem angelicus et divinus se habet sicut res incorruptibiles, quae statim a principio habent suam totam perfectionem. Unde intellectus angelicus et divinus statim perfecte totam rei cognitionem habet. Unde in cognoscendo quidditatem rei, cognoscit de re simul quidquid nos cognoscere possumus componendo et dividendo et ratiocinando. Et ideo intellectus humanus cognoscit componendo et dividendo, sicut et ratiocinando. Intellectus autem divinus et angelicus cognoscunt quidem compositionem et divisionem et ratiocinationem, non componendo et dividendo et ratiocinando, sed per intellectum simplicis quidditatis.

Ad 1

Ad primum ergo dicendum quod compositio et divisio intellectus secundum quandam differentiam vel comparationem fit. Unde sic intellectus cognoscit multa componendo et dividendo, sicut cognoscendo differentiam vel comparationem rerum.

Ad 2

Ad secundum dicendum quod intellectus et abstrahit a phantasmatibus; et tamen non intelligit actu nisi convertendo se ad phantasmata, sicut supra dictum est.

Et ex ea parte qua se ad phantasmata convertit, compositioni et divisioni intellectus adiungitur tempus.

Ad 3

Ad tertium dicendum quod similitudo rei recipitur in intellectu secundum modum intellectus, et non secundum modum rei.

Unde compositioni et divisioni intellectus respondet quidem aliquid ex parte rei; tamen non eodem modo se habet in re, sicut in intellectu. Intellectus enim humani proprium obiectum est quidditas rei materialis, quae sub sensu et imaginatione cadit.

Invenitur autem duplex compositio in re materiali. Prima quidem, formae ad materiam, et huic respondet compositio intellectus qua totum universale de sua parte praedicatur; nam genus sumitur a materia communi, differentia vero completiva speciei a forma, particulare vero a materia individuali. Secunda vero compositio est accidentis ad subiectum, et huic reali compositioni respondet compositio intellectus secundum quam praedicatur accidens de subiecto, ut cum dicitur, homo est albus. Tamen differt compositio intellectus a compositione rei, nam ea quae componuntur in re, sunt diversa; compositio autem intellectus est signum identitatis eorum quae componuntur. Non enim intellectus sic componit, ut dicat quod homo est albedo; sed dicit quod homo est albus, idest habens albedinem, idem autem est subiecto quod est homo, et quod est habens albedinem. Et simile est de compositione formae et materiae, nam animal significat id quod habet naturam sensitivam, rationale vero quod habet naturam intellectivam, homo vero quod habet utrumque, socrates vero quod habet omnia haec cum materia individuali; et secundum hanc identitatis rationem, intellectus noster unum componit alteri praedicando.