ART. I. -- UNION OF SOUL AND BODY.
95. Since the intellective soul is the substantial form of the body, it constitutes with it a substantial and personal union, so that from this union there results a single substance and person. Hence, as the soul without the body is not perfect in its operations, so the body without the soul has no subsistence of its own. -- In living composites the soul is the substantial form of the body; that is, the soul is so united to the body that through it the body receives and possesses subsistence and life, and that from the union of these two principles there results a single substance. So it is with man. From the union of his body and soul, from their intimate compenetration, there results a third substance which is neither body alone, nor soul alone, nor a simple contact or mixture of the two, as in a mixture of silver and gold. Still the soul in this union does not lose its own essence: although united to the body in unity of substance, it nevertheless remains distinct from the body; and since it performs certain acts independently of the body, it follows that it preserves its spiritual nature intact. The union of soul and body does not, then, mean a confusion of the two, but requires only that they complete each other. And as the single substance that results from the union of soul and body constitutes an individual of a rational nature, we must conclude that the union constitutes not only a substantial unity, but also a personal unity. The person is, therefore, not the body alone, not the soul alone, but the soul united to the body, as is further witnessed by language, which permits us to say: I hear, I understand, I desire, I run.
96. There are four striking errors regarding the union of soul and body. 1. The system of occasional causes; 2. That of preestablished harmony; 3. That of plastic medium; 4. That of physical influence. -- Several philosophers, and among them Plato of the ancient school, and Descartes of the modern, have denied the substantial unity of body and soul, and the reciprocal and immediate action of the soul on the body, and of the body on the soul. But as evidence shows the intimate relations existing between the soul and body, they have attempted to explain these relations. Now if, instead of regarding the soul and body as one clock, the hands and wheels of which are parts of one and the same mechanism, we regard them as two distinct clocks that go in accord, we may form four hypotheses analogous to those that would be formed for the two clocks. For either the clockmaker is always present to keep up the accord between these two clocks; or he may wind them up once for all, so that thenceforth there is perfect agreement between them; or this may be maintained by the aid of an intermediate mechanism; or, lastly, it may be the result of a physical influence exerted by one clock over the other in virtue of some secret power. Thus four systems have tried to explain the relations between the soul and body: the system of occasionalism, of preëstablished harmony, of plastic medium, and of physical influence.
97. It is false to hold with Malebranche that soul and body form two distinct substances; that God takes occasion from the motions of the body to produce corresponding acts in the soul, and takes occasion from the acts of the soul to produce corresponding motions in the body. This system leads to pantheism, fatalism, idealism, and scepticism. -- The system of occasionalism, advocated by Malebranche, is a consequence of his false principle, that God alone is a true cause and that creatures of themselves produce no effect. It results also from the false notion which, after Descartes, he had formed of the human soul and body; for he regarded them as two distinct substances forming only an accidental union. To hold with Malebranche that God alone establishes relations between soul and body, is to assign Him a ridiculous office, opposed equally to His holiness and His wisdom. For if God alone acts, we are destitute of all entity; this is downright pantheism. Now, if man be not the principle of his actions, we must admit that his acts are not free, and this is fatalism. Lastly, if all our thoughts are but the play of God upon our intelligence, if they have no direct relation with external reality, the material world and our bodies are for us as though they did not exist, and this is idealism. And since in invincibly believing ourselves to be the principle of our acts we are in a constant illusion, we can no longer be certain of anything; this is scepticism.
98. We cannot admit with Leibnitz that God, at the moment of their union, secures the constant relations existing between body and soul, in virtue of a preestablished harmony. -- This system involves nearly the same consequences as occasionalism. Leibnitz has not denied to second causes an activity of their own, but, like Malebranche, he has failed to recognize a true reciprocity of action between body and soul. According to him, before God united the soul to the body, He so constituted them that the motions of the body would be constantly in harmony with the actions of the soul. This system ascribes to God a less ridiculous office; for it does not destroy all action on the part of the creature. But as it asserts that all acts, whether of soul or body, are invariably predetermined by an inevitable law, it is manifest that it leads directly to fatalism, idealism, and scepticism.
99. It is absurd to admit with certain philosophers something intermediate between soul and body, called the plastic medium, by which the soul acts on the body and the body on the soul. -- This theory to explain the relations of soul and body, attributed to the English philosopher Cudworth (1617-1688), supposes that there exists as a bond of union between soul and body a substance that is at once material and immaterial, which holds communication with the body through its material part, and with the soul through its immaterial part. But, in the first place, such a substance is metaphysically impossible; and, in the second place, the reciprocal action of matter on spirit and spirit on matter in this intermediate substance remains to be explained.
100. The system of physical influence either is nothing but materialism or it explains nothing. -- The English school, in setting up this system of physical influence, considers the soul as extremely subtile matter, and from this infers that the action of the soul on the body is analogous to that of fire on wood. But this is evidently pure materialism. Those philosophers also who, while admitting physical influence, defend the spirituality of the soul, are likewise at fault; for they regard the soul and body as two distinct beings. Moreover, their system explains nothing, for it simply teaches that the soul exerts an influence on the body and the body on the soul.
ART. II. -- UNITY OF THE HUMAN SOUL AS SUBSTANTIAL FORM OF THE BODY.
101. There is but one human soul, which is the substantial form of the body. This soul is intellective, and, besides intellective life, possesses also sensitive life and vegetative life. -- By the very fact that in every natural composite it is the substantial form that gives being to the composite, this form must be unique; for, if there were a plurality of forms, there would also be a plurality of beings, and the composite would lose its substantial unity. Hence in the living composite, and more particularly in man, the rational soul must be the unique form of the body, since it is its substantial form. Without doubt, the difference between the acts performed by one and the same living being, would seem to necessitate the referring of them to distinct principles. But it is with forms as with numbers: just as any number includes the units of a lower number, and one or more units besides, so every form has, besides its own specific virtue, that of the inferior forms also. Thus it is with the human soul, which is at once vegetative, sensitive, and intellective. This truth is confirmed by experience and Common sense: by experience, which testifies that in each individual it is always the same person that wills, sees, and is nourished; by common sense, which as expressed in language does not point to distinct principles of action in man. But it must be observed that when the intellective soul is called the form of the body, we thereby mean simply that the three kinds of life -- vegetative, sensitive, and intellective -- have in man a single principle; not that the soul communicates all its powers to the body. It communicates those only that require organs for their exercise, and reserves to itself the intellect and will, which are independent of the body. Hence the human soul is the form of the body inasmuch as it contains the virtue of the vegetative and the sensitive principle: not as being the rational principle in man.
102. A plurality of souls, taught by several ancient philosophers, makes the unity of the human composite inexplicable. -- Several ancient philosophers, disregarding the substantial union of soul and body in man, were forced to attribute several souls to him. For if the soul is united to the body as the motor to the movable object, there is nothing to prevent the existence of many media between the motor and the object, even of many motors, especially if the movable object be impelled in different ways. By such reasoning was Plato drawn into distinguishing three souls in man -- a vegetative, a sensitive, and an intellectual soul.
But this system is erroneous; for, as each soul has a distinct life and distinct operations, it should be independent of the other souls in its operations, and thus the unity of man would be destroyed. Besides, experience contradicts this doctrine; for it shows us that the acts of the vegetative and the sensitive life affect those also of the intellective life, and vice versa.
It is useless to assert that the union of the three souls would be established by the body which would contain them in itself, as a bookcase holds many volumes. Since the body has its being only through the soul, it is the soul that contains the body, and not the body that contains the soul. Nor can it be said that one soul is the substantial form of the body, and that the others are united to it accidentally. For this were tantamount to asserting that man is accidentally intelligent, or sentient, or vegetative, just as he is accidentally tall, learned, or courageous; but this is absurd.{1}
103. The modern theory of the "vital principle" is in substance only a reproduction of the error of a plurality of souls. The proofs and experiments on which it is based are valueless. -- The different systems by which it has been attempted in modern times to explain the life-principle in man refer to the question of the unity of the human soul. The three principal theories are, (1) the Animism of Stahl (1660-1734), according to whom the intellective soul through its inferior forms presides over the organic functions; (2) Organicism, held by Descartes, who regarded the organs themselves as the cause, through their physical forces, of the vital acts; (3) Duodynamism, formulated by Barthez (1734-1806), propagated by the school of Montpellier, and advocated in Germany by Günther (1785-1863); it is so called because it supposes two distinct principles in man, the soul to preside over intellectual functions, and the vital principle to regulate organic life.
In his system Stahl only reproduces, though with some errors, the doctrine of the substantial union of soul and body. The materialistic system of organicism is too much opposed to the data of physiology to claim disciples any longer.
The same is not true of the vitalism of Montpellier, which has seduced many by a specious appearance of elevated spiritualism. The duodynamists rest their arguments, first, upon the corruptibility of the sensitive life, which they claim cannot be referred to the intellective principle, for the intellective as such is incorruptible. This difficulty is removed by saying that nothing prevents an incorruptible substance from exercising corruptible functions; just as a king may for the nonce be soldier or judge. But if vital acts and intellectual operations must be ascribed to distinct principles, owing to the essential difference between them, we must still further multiply the number of souls in man; for the act of understanding differs essentially from that of willing, the act of perceiving from that of moving, and so of many other acts. The duodynamists also argue that, as the vital acts are accomplished without the knowledge of the intellective soul, therefore the intellective soul cannot be the principle of said acts. But though nature has willed that the vital functions be performed unconsciously, in order to their more secure fulfilment, it is none the less certain that the soul is made aware of these functions when they are attended with suffering. Lastly, the duodynamists invoke experience and bring forward certain phenomena, as, for example, the contractions sometimes observed in individuals immediately after death. But these phenomena are very rare, and may easily be explained by purely physical causes. Besides, if it were necessary to admit the conclusions drawn by these philosophers, we should eventually be compelled to allow that the body can continue to live after its separation from the soul. Such an issue no duodynamist would dare to sustain.
ART. III. -- SEAT OR LOCUS OF THE SOUL.
104. The soul is in its essence entire in the whole body and in every part of the body; but it does not exercise all its functions through corporeal organs, and it does not exercise the same functions in each corporeal organ. -- Several modern philosophers, from denying the substantial union of soul and body, have been led to examine what part of the body is the seat of the soul. Some have asserted that it is the brain, others that it is the heart, and still others that it is this or that part of the brain. All these statements fall wide of the mark. For (1) the soul is the principle of life in the body; now all the parts of the body are living; therefore the soul is in every part of the body. (2) The same conclusion is drawn from the fact that the soul is the principle of sensation, and that it is sentient in each part of the body.
On the other hand, as the soul is indivisible, it must be entire wherever it is; therefore the soul is entire in every part of the body. But, although the soul is in its essence entire in every part of the body, it does not exercise all its functions through bodily organs, because the functions that require the concurrence of an organ necessarily vary with the different nature of the organs themselves. The peculiar action of the soul experienced in the brain and in the heart is easily explained by the fact that these two parts of the body are the principal organs of sensibility and life, respectively.
Some philosophers object that if the soul be in every part of the body, it is extended, and therefore material. This is readily answered. Bodies are in place circumscriptively, since they are circumscribed in their dimensions by the place which they occupy; immaterial creatures are in place determinatively, since they are not measured by it but only so determined that they exercise their power in this place, and cannot be at the same time in another place. Thus the soul is in the body, not because the body contains it, measures it, or circumscribes it, but because the body is the subject of its operations, and because the soul contains it, so to say, by giving it being and unity.
ART. IV. -- THE RESURRECTION OF THE BODY.
105. Since the soul is made to be united with the body, it will again be united to it after having been separated from it for a time. This reunion is demanded not only by the very nature of man, but likewise by the moral order, according to which the body will share in the reward or punishment of the good or evil of which it shall have been the instrument. -- Man is neither soul alone nor body alone; his being is complete only when his soul is substantially united to his body. Undoubtedly the human soul is subsistent in itself; but God has placed it lowest in the order of intelligences, and on account of its weakness it requires the body for the perfection and integrity of its specific operations. Since, then, the body is an integral part of man's nature, it must be resuscitated; otherwise we should be obliged to say that man, the work of divine predilection, would remain forever in a state contrary to nature. But this cannot be. God has allowed sin to subvert for a time the order of His Providence, but not to triumph forever over the laws that He has established. To this reason, derived from man's nature, may be added another, drawn from the end for which the body was originally created immortal. When God made the soul subsistent in itself, in order to proportion the matter to the form He willed, by a special gift, to make the body share in the soul's immortality. But, if by the fall the body has become mortal, the soul is none the less immortal, and therefore the cause for which an immortal body had at first been given to it still exists.
Therefore, in order not to change the end for which He first made the body immortal, God in a manner owes it to Himself to restore to it for the soul's sake the primitive privilege of incorruptibility. Hence it is evident that the resurrection of the body is not something outside the laws of the natural order; but that it is, on the contrary, the restoration of the order originally established by God. If there is any miracle in the resurrection; it is only in view of the cause that will work it, which can be nothing but the power of God, and not in view of the natural exigency which we have just explained. These arguments for the resurrection of the body are confirmed by reasons drawn both from the moral order, which require that the body, the instrument of the good or evil wrought by the soul, should share in its reward or punishment; and from the order of nature, where everything is unceasingly dying to resume a new life, and where man would be an exception without explanation, if he should die to live no more.
106. It is absurd to object against the resurrection of the body that it is impossible for the scattered elements of the body to be reunited, or that it is impossible for the soul to resume its former body, which will have been transformed into an infinity of other substances: for in the former case, we put limits to God's power; in the latter, we forget that identity of molecules is not necessary to constitute identity of body. -- To assert with materialists that when the elements of the body have once been separated, it is impossible to unite them again to reconstitute the body, is to put limits to the power of God, who was able to draw the body out of nothingness, and who a fortiori can reform it with its primitive elements. But some philosophers raise the objection that since the body is transformed into an infinity of other substances, it can no longer be reconstituted with molecules numerically the same, and that, as God thus gives a new body to the soul, all the reasons alleged in support of the resurrection lose their value. The objection falls; for, in the first place, it is not impossible for God to reconstitute the body with the same molecules that it had before; and, in the second place, identity of molecules is by no means necessary to secure identity of body. For science has shown that the body, properly so called, is not constituted of the molecules that enter into it, since these molecules are renewed day by day and are all changed in the space of about seven years, while the body remains ever the same.
{1} The doctrine of Photius that man has two souls, one rational, the other irrational, and that sin is the act of the latter, was condemned by the Fourth General Council of Constantinople (869). In the middle ages the error was revived by Ockham, and only thirty years ago by a German Catholic, Dr. Günther. -- The General Council of Vienne condemned as erroneous and un-Catholic the denial that "the substance of the rational or intellectual soul is truly and in itself the form of the human body."