SUMMA THEOLOGICA. Thomas Aquinas
these a greater variety than in plants.
Reply to Objection 4: The intellectual soul as comprehending universals, has a power extending to the infinite; therefore it cannot be limited by nature to certain fixed natural notions, or even to certain fixed means whether of defence or of clothing, as is the case with other animals, the souls of which are endowed with knowledge and power in regard to fixed particular things. Instead of all these, man has by nature his reason and his hands, which are "the organs of organs" (De Anima iii), since by their means man can make for himself instruments of an infinite variety, and for any number of purposes.
Whether the intellectual soul is united to the body through the medium of accidental dispositions?
Objection 1: It would seem that the intellectual soul is united to the body through the medium of accidental dispositions. For every form exists in its proper disposed matter. But dispositions to a form are accidents. Therefore we must presuppose accidents to be in matter before the substantial form; and therefore before the soul, since the soul is a substantial form.
Objection 2: Further, various forms of one species require various parts of matter. But various parts of matter are unintelligible without division in measurable quantities. Therefore we must suppose dimensions in matter before the substantial forms, which are many belonging to one species.
Objection 3: Further, what is spiritual is connected with what is corporeal by virtual contact. But the virtue of the soul is its power. Therefore it seems that the soul is united to the body by means of a power, which is an accident.
On the contrary, Accident is posterior to substance, both in the order of time and in the order of reason, as the Philosopher says, Metaph. vii (Did. vi, 1). Therefore it is unintelligible that any accidental form exist in matter before the soul, which is the substantial form.
I answer that, If the soul were united to the body, merely as a motor, there would be nothing to prevent the existence of certain dispositions mediating between the soul and the body; on the contrary, they would be necessary, for on the part of the soul would be required the power to move the body; and on the part of the body, a certain aptitude to be moved by the soul.
If, however, the intellectual soul is united to the body as the substantial form, as we have already said above ( Article [1]), it is impossible for any accidental disposition to come between the body and the soul, or between any substantial form whatever and its matter. The reason is because since matter is in potentiality to all manner of acts in a certain order, what is absolutely first among the acts must be understood as being first in matter. Now the first among all acts is existence. Therefore, it is impossible for matter to be apprehended as hot, or as having quantity, before it is actual. But matter has actual existence by the substantial form, which makes it to exist absolutely, as we have said above ( Article [4]). Wherefore it is impossible for any accidental dispositions to pre-exist in matter before the substantial form, and consequently before the soul.
Reply to Objection 1: As appears from what has been already said ( Article [4]), the more perfect form virtually contains whatever belongs to the inferior forms; therefore while remaining one and the same, it perfects matter according to the various degrees of perfection. For the same essential form makes man an actual being, a body, a living being, an animal, and a man. Now it is clear that to every "genus" follow its own proper accidents. Therefore as matter is apprehended as perfected in its existence, before it is understood as corporeal, and so on; so those accidents which belong to existence are understood to exist before corporeity; and thus dispositions are understood in matter before the form, not as regards all its effects, but as regards the subsequent effect.
Reply to Objection 2: Dimensions of quantity are accidents consequent to the corporeity which belongs to the whole matter. Wherefore matter, once understood as corporeal and measurable, can be understood as distinct in its various parts, and as receptive of different forms according to the further degrees of perfection. For although it is essentially the same form which gives matter the various degrees of perfection, as we have said (ad 1), yet it is considered as different when brought under the observation of reason.
Reply to Objection 3: A spiritual substance which is united to a body as its motor only, is united thereto by power or virtue. But the intellectual soul is united by its very being to the body as a form; and yet it guides and moves the body by its power and virtue.
Whether the soul is united to the animal body by means of a body?
Objection 1: It seems that the soul is united to the animal body by means of a body. For Augustine says (Gen. ad lit. vii, 19), that "the soul administers the body by light," that is, by fire, "and by air, which is most akin to a spirit." But fire and air are bodies. Therefore the soul is united to the human body by means of a body.
Objection 2: Further, a link between two things seems to be that thing the removal of which involves the cessation of their union. But when breathing ceases, the soul is separated from the body. Therefore the breath, which is a subtle body, is the means of union between soul and body.
Objection 3: Further, things which are very distant from one another, are not united except by something between them. But the intellectual soul is very distant from the body, both because it is incorporeal, and because it is incorruptible. Therefore it seems to be united to the body by means of an incorruptible body, and such would be some heavenly light, which would harmonize the elements, and unite them together.
On the contrary, The Philosopher says (De Anima ii, 1): "We need not ask if the soul and body are one, as neither do we ask if wax and its shape are one." But the shape is united to the wax without a body intervening. Therefore also the soul is thus united to the body.
I answer that, If the soul, according to the Platonists, were united to the body merely as a motor, it would be right to say that some other bodies must intervene between the soul and body of man, or any animal whatever; for a motor naturally moves what is distant from it by means of something nearer.
If, however, the soul is united to the body as its form, as we have said ( Article [1]), it is impossible for it to be united by means of another body. The reason of this is that a thing is one, according as it is a being. Now the form, through itself, makes a thing to be actual since it is itself essentially an act; nor does it give existence by means of something else. Wherefore the unity of a thing composed of matter and form, is by virtue of the form itself, which by reason of its very nature is united to matter as its act. Nor is there any other cause of union except the agent, which causes matter to be in act, as the Philosopher says, Metaph. viii (Did. vii, 6).
From this it is clear how false are the opinions of those who maintained the existence of some mediate bodies between the soul and body of man. Of these certain Platonists said that the intellectual soul has an incorruptible body naturally united to it, from which it is never separated, and by means of which it is united to the corruptible body of man. Others said that the soul is united to the body by means of a corporeal spirit. Others said it is united to the body by means of light, which, they say, is a body and of the nature of the fifth essence; so that the vegetative soul would be united to the body by means of the light of the sidereal heaven; the sensible soul, by means of the light of the crystal heaven; and the intellectual soul by means of the light of the empyrean heaven. Now all this is fictious and ridiculous: for light is not a body; and the fifth essence does not enter materially into the composition of a mixed body (since it is unchangeable), but only virtually: and lastly, because the soul is immediately united to the body as the form to matter.
Reply to Objection 1: Augustine speaks there of the soul as it moves the body; whence he uses the word "administration." It is true that it moves the grosser parts of the body by the