Of the Soul and the Body, and of Their Union and Separation and Return
Now let us refute the arguments of those who maintain the opposite opinions, which Lucretius has related in his third book. Since, he says, the soul is born together with the body, it must necessarily die with the body. But the two cases are not similar. For the body is solid, and capable of being grasped both by the eyes and the hand; but the soul is slight, and eluding the touch and sight. The body is formed from the earth, and made firm; the soul has in it nothing concrete, nothing of earthly weight, as Plato maintained. For it could not have such great force, such great skill, such great rapidity, unless it derived its origin from heaven. The body, therefore, since it is made up of a ponderous and corruptible element, and is tangible and visible, is corrupted and dies; nor is it able to repel violence, because it comes under the sight and under the touch; but the soul, which by its slightness avoids all touch, can be dissolved by no attack. Therefore, although they are joined and connected together from birth, and the one which is formed of earthly material is, as it were, the vessel of the other, which is drawn out from heavenly fineness, when any violence has separated the two, which separation is called death, then each returns into its own nature; that which was of earth is resolved into earth; that which is of heavenly breath remains fixed, and flourishes always, since the divine spirit is everlasting. In fine, the same Lucretius, forgetting what he asserted, and what dogma he defended, wrote these verses: —
“That also which before was from the earth passes back into the earth, and that which was sent from the borders of ether is carried again by the quarters of heaven.”
But this language was not for him to employ, who contended that souls perished with the bodies; but he was overcome by the truth, and the true system stole upon him unawares. Moreover, that very inference which he draws, that the soul suffers dissolution, that is, that it perishes together with the body, since they are produced together, is both false, and is capable of being turned to the opposite direction. For the body does not perish together with the soul; but when the soul departs it remains entire for many days, and frequently by medical preparations it remains entire for a very long time. For if they both perished together, as they are produced together, the soul would not hastily depart and desert the body, but both would be dispersed alike at one point of time; and the body also, while the breath still remained in it, would dissolve and perish as quickly as the soul departs: yes, truly, the body, being dissolved, the soul would vanish, as moisture poured forth from a broken vessel. For if the earthly and frail body after the departure of the soul does not immediately flow away and waste into earth, from which it has its origin, therefore the soul, which is not frail, endures to eternity, since its origin is eternal. He says, since the understanding increases in boys, and is vigorous in young men, and is lessened in the aged, it is evident that it is mortal. First, the soul is not the same thing as the mind; for it is one thing that we live, another that we reflect. For it is the mind of those who are asleep which is at rest, not the soul; and in those who are mad, the mind is extinguished, the soul remains; and therefore they are not said to be without a soul, but to be deprived of their mind. Therefore the mind, that is, the understanding, is either increased or lessened according to age. The soul is always in its own condition; and from the time when it receives the power of breathing, it remains the same even to the end, until, being sent forth from the confinement of the body, it flies back to its own abode. In the next place, the soul, although inspired by God, yet, because it is shut up in a dark abode of earthly flesh, does not possess knowledge, which belongs to divinity. Therefore it hears and learns all things, and receives wisdom by learning and hearing; and old age does not lessen wisdom, but increases it, if the age of youth has been passed in virtue; and if excessive old age shall have enfeebled the limbs, it is not the fault of the mind if the sight has vanished, if the tongue has become benumbed, if the hearing has grown deaf, but it is the fault of the body. But, it is said, the memory fails. What wonder, if the mind is oppressed by the ruin of the falling house, and forgets the past, not about to be divine on any other condition than if it shall have escaped the prison in which it is confined?
But the soul, he says, is also subject to pain and grief, and loses its senses through drunkenness, whence it is evidently frail and mortal. On this account, therefore, virtue and wisdom are necessary, that both grief, which is contracted by the suffering and the sight of unworthy objects, may be repelled by fortitude, and that pleasure may be overcome, not only by abstaining from drinking, but also from other things. For if it be destitute of virtue, if it be given up to pleasure, and thus rendered effeminate, it will become subject to death, since virtue, as we have shown, is the contriver of immortality, as pleasure is of death. But death, as I have set forth, does not entirely extinguish and destroy, but visits with eternal torments. For the soul cannot entirely perish, since it received its origin from the Spirit of God, which is eternal. The soul, he says, is sensible even of disease of the body, and suffers forgetfulness of itself; and as it grows ill, so also it is often healed. This is therefore the reason why virtue is especially to be used, that the mind— not the soul — may not be harassed by any pain of the body, or undergo oblivion of itself. And since this has its seat in a certain part of the body, when any violence of disease has vitiated that part, it is moved from its place; and as though shaken, it departs from its station, about to return when a cure and health shall have remodelled its abode. For, since the soul is united with the body, if it is destitute of virtue, it grows sick by the contagion of the body, and from sharing its frailty the weakness extends to the mind. But when it shall be disunited from the body it will flourish by itself; nor will it now be assailed by any condition of frailty, because it has laid aside its frail covering. As the eye, he says, when torn out and separated from the body, can see nothing, so also the soul, when separated, can perceive nothing, because it is itself also a part of the body. This is false, and dissimilar to the case supposed; for the soul is not a part of the body, but in the body. As that which is contained in a vessel is not a part of the vessel, and these things which are in a house are not said to be a part of the house; so the mind is not a part of the body, because the body is either the vessel or the receptacle of the soul.
Source: The Divine Institutes (New Advent)