AQUINAS ON IMMATERIALITY
Definitions
Sketch of Proof
Aquinas’ Proof of the Immateriality of
Thought
Aquinas’s thesis:
Sense perception is the function of a bodily organ, while understanding is not the function of a bodily organ
Proof:
* Per se sensibilia are sensible qualities which, as such, can directly affect one or more senses. Per accidens sensibilia are other sensible qualities, which are joined in the object to its per se sensible qualities. (Sugar cube: white, sweet, cubical, sugar.) Proper sensibilia are per se sensibilia which, as such, can directly affect only one of the senses. Common sensibilia are per se sensibilia which directly affect any and all of the senses. This is because common sensibilia are the necessary spatio-temporal determinations of all proper sensibilia. These determinations can be represented only by the corresponding determinations of the representing act; thus it also has to be material.
Sensus est singularium itellectus universalium
377. Concerning what is said here, we have to ask ourselves (a) why sensation is of individual things, whereas science is of universals; and (b) how exactly universals exist in the soul.
As to (a) we should note that while the sense-faculty is always the function of a bodily organ, intellect is an immaterial power--it is not the actuality of any bodily organ. Now everything received is received in the mode of the recipient. If then all knowledge implies that the thing known is somehow present in the knower (present by its similitude), the knower's actuality as such being the actuality of the thing known, it follows that the sense-faculty receives a similitude of the thing sensed in a bodily and material way, whilst the intellect receives a similitude of the thing understood in an incorporeal and immaterial way. Now in material and corporeal beings the common nature derives its individuation from matter existing within specified dimensions, whereas the universal comes into being by abstraction from such matter and all the individuating material conditions. Clearly, then, a thing's similitude as received in sensation represents the thing as an individual; as received, however, by the intellect it represents the thing in terms of a universal nature. That is why individuals are known by the senses, and universals (of which are the sciences) by the intellect.
378. As to (b), note that the term 'universal' can be taken in two senses. It can refer to the nature itself, common to several things, in so far as this common nature is regarded in relation to those several things; or it can refer to the nature taken simply in itself. Similarly, in a 'white thing' we can consider either the thing that happens to be white or the thing precisely as white. Now a nature--say, human nature,--which can be thought of universally, has two modes of existence: one, material, in the matter supplied by nature; the other, immaterial, in the intellect. As in the material mode of existence it cannot be represented in a universal notion, for in that mode it is individuated by its matter; this notion only applies to it, therefore, as abstracted from individuating matter. But it cannot, as so abstracted, have a real existence, as the Platonists thought; man in reality only exists (as is proved in the Metaphysics, Book VII)^1 in this flesh and these bones. Therefore it is only in the intellect that human nature has any being apart from the principles which individuate it.
379. Nevertheless, there is no deception when the mind apprehends a common nature apart from its individuating principles; for in this apprehension the mind does not judge that the nature exists apart; it merely apprehends this nature without apprehending the individuating principles; and in this there is no falsehood. The alternative would indeed be false--as though I were so to discriminate whiteness from a white man as to understand him not to be white. This would be false; but not if I discriminate the two in such wise as to think of the man without giving a thought to his whiteness. For the truth of our conceptions does not require that, merely apprehending anything, we apprehend everything in it. Hence the mind abstracts, without any falsehood, a genus from a species when it understands the generic nature without considering the differences; or it may abstract the species from individuals when it understands the specific nature, without considering the individuating principles.
380. It is clear, then, that universality can be predicated of a common nature only in so far as it exists in the mind: for a unity to be predicable of many things it must first be conceived apart from the principles by which it is divided into many things. Universals as such exist only in the soul; but the natures themselves, which are conceivable universally, exist in things. That is why the common names that denote these natures are predicated of individuals; but not the names that denote abstract ideas. Socrates is a 'man', not a 'species'--although 'man' is a 'species'. [In de Anima, bk. 2. lc. 12.]
393. So we must look for another answer. We have seen that sensation is a being acted upon and altered in some way. Whatever, then, affects the faculty in, and so makes a difference to, its own proper reaction and modification has an intrinsic relation to that faculty and can be called a sense-object in itself or absolutely. But whatever makes no difference to the immediate modification of the faculty we call an incidental sense-object. Hence, the Philosopher says explicitly that the senses are not affected at all by the incidental object as such.
394. Now an object may affect the faculty's immediate reaction in two ways. One way is with respect to the kind of agent causing this reaction; and in this way the immediate objects of sensation differentiate sense-experience, inasmuch as one such object is color, another is sound, another white, another black, and so on. For the various kinds of stimulants of sensation are, in their actuality as such, precisely the special sense-objects themselves; and to them the sense-faculty (as a whole) is by nature adapted; so that precisely by their differences is sensation itself differentiated.
On the other hand there are objects which differentiate sensation with respect, not to the kind of agent, but to the mode of its activity. For as sense-qualities affect the senses corporeally and locally, they do so in different ways, if they are qualities of large or small bodies or are diversely situated, i.e. near, or far, or together, or apart. And it is thus that the common sensibles differentiate sensation. Obviously, size and position vary for all the five senses. And not being related to sensation as variations in the immediate factors which bring the sense into act, they do not properly differentiate the sense-faculties; they remain common to several faculties at once. [In de Anima, bk. 2. lc. 13.]
002 2SN IN II SENTENTIARUM DS19QU1 AR1-CO--
Respondeo dicendum, quod circa hoc quatuor sunt positiones. Prima fuit antiquorum naturalium, qui intellectum a sensu non discernebant; unde sicut operatio sensus dependet a corpore, ita etiam ponebant intellectus operationem ex corpore dependere et animam intellectivam consequi naturam corporalem: unde quidam ponebant animam esse ignem, quidam vaporem, quidam harmoniam, et sic de aliis, secundum quod tantum sensus et motus animalium considerabant; et ideo secundum eos necessarium fuit ponere animam post corpus non remanere. Hanc autem opinionem aristoteles, sufficienter infringit, ostendens intellectum habere esse absolutum, non dependens a corpore; propter quod dicitur non esse actus corporis; et ab avicenna dicitur non esse forma submersa in materia; et in libro de causis dicitur non esse super corpus delata. Hujus autem probationis medium sumitur ex parte operationis ejus. Cum enim operatio non possit esse nisi rei per se existentis, oportet illud quod per se habet operationem absolutam, etiam esse absolutum per se habere. Operatio autem intellectus est ipsius absolute, sine hoc quod in hac operatione aliquod organum corporale communicet; quod patet praecipue ex tribus. Primo, quia haec operatio est omnium formarum corporalium sicut objectorum; unde oportet illud principium cujus est haec operatio, ab omni forma corporali absolutum esse. Secundo, quia intelligere est universalium; in organo autem corporali recipi non possunt nisi intentiones individuatae. Tertio, quia intellectus intelligit se; quod non contingit in aliqua virtute cujus operatio sit per organum corporale; cujus ratio est, quia secundum avicennam, cujuslibet virtutis operantis per organum corporale, oportet ut organum sit medium inter ipsam et objectum ejus. Visus enim nihil cognoscit nisi illud cujus species potest fieri in pupilla. Unde cum non sit possibile ut organum corporale cadat medium inter virtutem aliquam et ipsam essentiam virtutis, non erit possibile ut aliqua virtus operans mediante organo corporali cognoscat seipsam. Et haec probatio tangitur in libro de causis in illa propositione 15: omnis sciens qui scit essentiam suam, est rediens ad essentiam suam reditione completa. Et dicitur redire complete ad essentiam, ut ibi commentator exponit, cujus essentia est fixa stans, non super aliud delata. Ex quibus omnibus patet quod anima intellectiva habet esse absolutum, non dependens ad corpus; unde corrupto corpore non corrumpitur. Secunda fuit pythagorae et platonis, qui videntes incorruptionem animae, erraverunt in hoc quod posuerunt animas de corpore in corpus transire. Et hanc positionem improbat philosophus in 1 de anima, ostendens quod anima est forma corporis et motor ejus. Oportet autem ut determinatae formae determinata materia debeatur, et determinato motori determinatum organum, sicut quaelibet ars in agente utitur propriis instrumentis: unde haec anima non potest esse forma et motor nisi hujus corporis. Tertia positio est eorum qui dicunt, animam intellectivam secundum quid corruptibilem esse, et secundum quid incorruptibilem; quia secundum hoc quod de anima est huic corpori proprium, corrumpitur corrupto corpore; secundum autem id quod omnibus est commune, incorruptibilis est. Ponunt enim intellectum esse unum in substantia omnium; quidam agentem, et quidam possibilem, ut supra dictum est, dist. 17: et hunc esse substantiam incorruptibilem, et in nobis non esse nisi phantasmata illustrata lumine intellectus agentis, et moventia intellectum possibilem, quibus intelligentes sumus, secundum quod per ea continuamur intellectui separato. Ex quo sequitur quod si id quod est proprium, destruitur, tantum communi remanente, ex omnibus animabus humanis una tantum substantia remaneat, dissolutis corporibus. Haec autem positio quibus rationibus innitatur, et quomodo improbari possit, supra dictum est, 17 dist.. Quarta positio est quam fides nostra tenet, quod anima intellectiva sit substantia non dependens ex corpore, et quod sint plures intellectivae substantiae secundum corporum multitudinem, et quod destructis corporibus remanent separatae, non in alia corpora transeuntes; sed in resurrectione idem corpus numero quod deposuerat unaquaeque assumat.