Reply. We confess that the potential intellect is specifically one in different men, and many according to number, -- waiving the point that the constituents of man are not put into genus and species for what they are in themselves, but for what they are as constituents of the whole. Still it does not follow that the potential intellect is a material form, dependent for its being on the body. For as it is specifically proper to the human soul to be united to a certain species of body, so any individual soul differs from any other individual soul, in number only, inasmuch as it is referable to numerically another body. Thus then human souls, -- and consequently the potential intellect, which is a faculty of the human soul, -- are individualised according to bodies, not that the individuation is caused by the bodies.*
Arg. 2. If the potential intellect were different in this man and that, the impression understood would have to be numerically different in this man, while remaining one in species: for since the proper subject of impressions actually understood is the potential intellect, when that intellect is multiplied there must be a corresponding multiplication of intellectual impressions according to the number of different individuals. But the only impressions or forms which are the same in species and different in number, are individual forms, which cannot be intellectual forms, because objects of intellect are universal, not particular. It is impossible therefore for the potential intellect to be multiplied in different individual men.*
Reply. This second argument fails from neglecting to distinguish between that whereby (quo) we understand, and that which (quod) we understand. The impression received in the potential intellect is not to be taken for that which is understood. For as all arts and sciences have for their object-matter things which are understood, it would follow that the subject-matter of all sciences was impressions on the potential intellect: which is manifestly false, for no science has anything to say to such mental impressions except psychology and metaphysics: though it is true that through those mental impressions there is known the whole content of all the sciences.* Therefore, in the process of understanding, the intellectual impression received in the potential intellect is that whereby we understand, as the impression of colour in the eye is not that which is seen, but that whereby we see. On the other hand, that which is understood is the nature (ratio) of things existing outside the soul, as also it is things existing outside the soul that are seen with the bodily sight: for to this end were arts and sciences invented, that things might be known in their natures (naturis).
Still it does not follow that, if sciences are of universal truths, universals should subsist by themselves outside the soul, as Plato supposed. For though for the truth of knowledge it is necessary that the knowledge should answer to the thing, still it is not necessary that the mode of the knowledge and the mode of the thing should be the same: for properties that are united in the thing are sometimes known separately. Thus one and the same thing is white and sweet: still sight takes cognisance only of the whiteness, and taste only of the sweetness. Thus again intellect understands a line drawn in sensible matter apart from that sensible matter, though it might understand it also along with the sensible matter.* This difference arises according to the diversity of intellectual impressions received in the intellect, which some times are the likeness of quantity only, sometimes of a sensible quantitative substance. In like manner also, though the nature of genus and species never exists except in concrete individuals, still the intellect understands the nature of genus and species without understanding the individualising elements; and this is the meaning of understanding universals. And so these two positions are reconciled, that universals have no subsistence outside the soul; and yet that the intellect, understanding universals, understands things which are outside the soul.
The fact of the intellect understanding the nature of genus and species stripped of its individualising elements, arises from the condition of the intellectual impression received in understanding, which impression is rendered immaterial* by the active intellect, inasmuch as it is abstracted from matter and materialising conditions whereby a thing is individualised. And therefore the sentient faculties can take no cognisance of universals, since they cannot receive an immaterial form, seeing that they receive always in a bodily organ.
It is not therefore necessary that the intellectual impression of this and that intelligence should be numerically one: for it would follow thereupon that the act of understanding in them both was also numerically one, since activity follows form, which is the principle of species: but it is necessary, to the end that one object should be understood by both minds, that there should be a like impression of one and the same object in them both. And this is possible enough, although the intellectual impressions differ in number: for there is no difficulty in having different images of one thing; hence the contingency of one than being seen by several persons.* There is nothing inconsistent then with the universalising knowledge of the understanding in their being different intellectual impressions in different minds. Nor need it ensue, because these intellectual impressions are many in number and the same in species, that they are not actual but only potential terms of understanding, as is the case with other individual things. Mere individuality is not inconsistent with intelligibility: for we must admit the potential and active intellects themselves, if we may suppose the two to subsist apart, united to no body, but subsistent by themselves, to be individual beings and still intelligible. What is inconsistent with intelligibility is materiality: as is shown by this consideration, that for the forms of material things to become actually intelligible, abstraction has to be made from the particular matter in which they are lodged;* and therefore in cases in which individuation is due to particular matter involving particular dimensions,* the things so individualised are not actually intelligible. But where individuation is not due to matter, such individual things may without difficulty be actually intelligible. Now intellectual impressions, like all other forms, are individualised by their subject, which is the potential intellect; and since the potential intellect is not material, it does not stand in the way of the actual intelligibility of the impressions individualised by it.
But though we have said that the intellectual impression, received in the potential intellect, is not that which is understood, but that whereby we understand, still it remains true that by reflection the intellect understands itself and its own intellectual act and the impression whereby it understands. Its own intellectual act it understands in two ways, -- in one way, in particular, for it understands that it is now understanding; in another way, in general, inasmuch as it reasons about the said act. And likewise it understands intellect and the impression in intellect in two ways, -- by remarking that itself is and has an intellectual impression, which is particular knowledge; and by studying its own nature and the nature of the intellectual impression, which is knowledge of the universal. According to this latter way we treat of intellect and of the intelligible in science.
Arg. 3. The master transfuses the knowledge which he has into the scholar. Either then the knowledge transfused is the same in number, or different in number, though the same in species. The latter alternative seems impossible: because it supposes the master to cause his own knowledge in the scholar in the same way that an agent causes its own form in another being, by generating a nature specifically like its own; which seems proper to material agents. It must be then that numerically the same knowledge is caused in the scholar that was in the master; which would be impossible, were there not one potential intellect of them both.
Reply. The saying that the knowledge in master and scholar is numerically one, is partly true and partly not: it is numerically one in point of the thing known, but not in point of the intellectual impressions whereby the thing is known, nor in point of the habit of knowledge itself. It is to be observed however that, as Aristotle (Metaph. VII, ix) teaches, there are arts in whose subject matter there is not any principle active in producing the effect of the art, as is clear in the building art: for in wood and stones there is no active power moving to the erection of a house, but only a passive aptitude. But there is an art in whose subject matter there is an active principle moving in the direction of the effect of the art, as is clear in the healing art: for in the sick subject there is an active principle tending to health. And therefore the effect of the former kind of art is never produced by nature, but always by art, as every house is a work of art:* but the effect of the latter kind is produced as well by art as by nature without art: for many are healed by the operation of nature without the art of medicine. In these things that can be done both by art and nature, art imitates nature: thus if one is sick of a chill, nature heals him by warming him: hence the physician also, if he is to cure him, heals him by warming. Similar is the case with the art of teaching: for in the pupil there is an active principle making for knowledge, namely, the understanding, and those primary axioms which are naturally understood; and therefore knowledge is acquired in two ways, -- without teaching, by a man's own finding out, and again by teaching. The teacher therefore begins to teach in the same way that the discoverer begins to find out, by offering for the consideration of the scholar elements of knowledge already possessed by him: because all education and all knowledge starts from pre-existing knowledge, drawing conclusions from elements already in the mind, and proposing sensible examples whereby there may be formed in the scholar's soul those impressions of phantasy which are necessary or intelligence.* And because the working of the teacher from without would effect nothing, unless borne out by an internal principle of knowledge, which is within us by the gift of God, so it is said among theologians that man teaches by rendering the service of ministry, but God by working within: so too the physician is called nature's minister in healing.
A final remark. Since the Commentator makes the passive intellect the residence of habits of knowledge (Chap. LX), the unity of the potential intellect helps not at all to the numerical unity of knowledge in master and scholar: for certainly the passive intellect is not the same in different men, since it is an organic faculty. Hence, on his own showing, this argument does not serve his purpose.
2.74 : Of the Opinion of Avicenna, who supposed Intellectual Forms not to be preserved in the Potential Intellect
2.76 : That the Active Intellect is not a separately Subsisting Intelligence, but a Faculty of the Soul