4 But why say more as to this? I must rather address myself to the question which you propose. In the first place, I wish you to understand that the Christian doctrine does not hold that the Godhead was so blended with the human nature in which He was born of the virgin that He either relinquished or lost the administration of the universe, or transferred it to that body as a small and limited material substance. Such an opinion is held only by men who are incapable of conceiving of anything but material substances— whether more dense, like water and earth, or more subtle, like air and light; but all alike distinguished by this condition, that none of them can be in its entirety everywhere, because, by reason of its many parts, it cannot but have one part here, another there, and however great or small the body may be, it must occupy some place, and so fill it that in its entirety it is in no one part of the space occupied. And hence it is the distinctive property of material bodies that they can be condensed and rarefied, contracted and dilated, crushed into small fragments and enlarged to great masses. The nature of the soul is very far different from that of the body; and how much more different must be the nature of God, who is the Creator of both soul and body! God is not said to fill the world in the same way as water, air, and even light occupy space, so that with a greater or smaller part of Himself He occupies a greater or smaller part of the world. He is able to be everywhere present in the entirety of His being: He cannot be confined in any place: He can come without leaving the place where He was: He can depart without forsaking the place to which He had come.
5. The mind of man wonders at this, and because it cannot comprehend it, refuses, perhaps, to believe it. Let it, however, not go on to wonder incredulously at the attributes of the Deity without first wondering in like manner at the mysteries within itself; let it, if possible, raise itself for a little above the body, and above those things which it is accustomed to perceive by the bodily organs, and let it contemplate what that is which uses the body as its instrument. Perhaps it cannot do this, for it requires, as one has said, great power of mind to call the mind aside from the senses, and to lead thought away from its wonted track. Let the mind, then, examine the bodily senses in this somewhat unusual manner, and with the utmost attention. There are five distinct bodily senses, which cannot exist either without the body or without the soul; because perception by the senses is possible, on the one hand, only while a man lives, and the body receives life from the soul; and on the other hand, only by the instrumentality of the body vessels and organs, through which we exercise sight, hearing, and the three other senses. Let the reasoning soul concentrate attention upon this subject, and consider the senses of the body not by these senses themselves, but by its own intelligence and reason. A man cannot, of course, perceive by these senses unless he lives; but up to the time when soul and body are separated by death, he lives in the body. How, then, does his soul,which lives nowhere else than in his body, perceive things which are beyond the surface of that body? Are not the stars in heaven very remote from his body? And yet does he not see the sun yonder? And is not seeing an exercise of the bodily senses— nay, is it not the noblest of them all? What, then? Does he live in heaven as well as in his body, because he perceives by one of his senses what is in heaven, and perception by sense cannot be in a place where there is no life of the person perceiving? Or does he perceive even where he is not living— because while he lives only in his own body, his perceptive sense is active also in those places which, outside of his body and remote from it, contain the objects with which he is in contact by sight? Do you see how great a mystery there is even in a sense so open to our observation as that which we call sight? Consider hearing also, and say whether the soul diffuses itself in some way abroad beyond the body. For how do we say, “Some one knocks at the door,” unless we exercise the sense of hearing at the place where the knock is sounding? In this case also, therefore, we live beyond the limits of our bodies. Or can we perceive by sense in a place in which we are not living? But we know that sense cannot be in exercise where life is not.
6. The other three senses are exercised through immediate contact with their own organs. Perhaps this may be reasonably disputed in regard to the sense of smell; but there is no controversy as to the senses of taste and touch, that we perceive nowhere else than by contact with our bodily organism the things which we taste and touch. Let these three senses, therefore, be set aside from present consideration. The senses of sight and hearing present to us a wonderful question, requiring us to explain either how the soul can perceive by these senses in a place where it does not live, or how it can live in a place where it is not. For it is not anywhere but in its own body, and yet it perceives by these senses in places beyond that body. For in whatever place the soul sees anything, in that place it is exercising the faculty of perception, because seeing is an act of perception; and in whatever place the soul hears anything, in that place it is exercising the faculty of perception, because hearing is an act of perception. Wherefore the soul is either living in that place where it sees or hears, and consequently is itself in that place, or it exercises perception in a place where it is not living, or it is living in a place and yet at the same moment is not there. All these things are astonishing; not one of them can be stated without seeming absurdity; and we are speaking only of senses which are mortal. What, then, is the soul itself which is beyond the bodily senses, that is to say, which resides in the understanding whereby it considers these mysteries? For it is not by means of the senses that it forms a judgment concerning the senses themselves. And do we suppose that something incredible is told us regarding the omnipotence of God, when it is affirmed that the Word of God, by whom all things were made, did so assume a body from the Virgin, and manifest Himself with mortal senses, as neither to destroy His own immortality, nor to change His eternity, nor to diminish His power, nor to relinquish the government of the world, nor to withdraw from the bosom of the Father, that is, from the secret place where He is with Him and in Him?
Source: Letters (New Advent)