But Celsus, lingering over matters which he does not understand, leads us to be guilty of tautology, as we do not wish even in appearance to leave any one of his objections unexamined. He proceeds, accordingly, as follows: “God either really changes himself, as these assert, into a mortal body, and the impossibility of that has been already declared; or else he does not undergo a change, but only causes the beholders to imagine so, and thus deceives them, and is guilty of falsehood.
Now deceit and falsehood are nothing but evils, and would only be employed as a medicine, either in the case of sick and lunatic friends, with a view to their cure, or in that of enemies when one is taking measures to escape danger. But no sick man or lunatic is a friend of God, nor does God fear any one to such a degree as to shun danger by leading him into error.” Now the answer to these statements might have respect partly to the nature of the Divine Word, who is God, and partly to the soul of Jesus.
As respects the nature of the Word, in the same way as the quality of the food changes in the nurse into milk with reference to the nature of the child, or is arranged by the physician with a view to the good of his health in the case of a sick man or (is specially) prepared for a stronger man, because he possesses greater vigour, so does God appropriately change, in the case of each individual, the power of the Word to which belongs the natural property of nourishing the human soul.
And to one is given, as the Scripture terms it, “the sincere milk of the word;” and to another, who is weaker, as it were, “herbs;” and to another who is full-grown, “strong meat.” And the Word does not, I imagine, prove false to His own nature, in contributing nourishment to each one, according as he is capable of receiving Him. Nor does He mislead or prove false. But if one were to take the change as referring to the soul of Jesus after it had entered the body, we would inquire in what sense the term “change” is used.
For if it be meant to apply to its essence, such a supposition is inadmissible, not only in relation to the soul of Jesus, but also to the rational soul of any other being. And if it be alleged that it suffers anything from the body when united with it, or from the place to which it has come, then what inconvenience can happen to the Word who, in great benevolence, brought down a Saviour to the human race?— seeing none of those who formerly professed to effect a cure could accomplish so much as that soul showed it could do, by what it performed, even by voluntarily descending to the level of human destinies for the benefit of our race.
And the Divine Word, well knowing this, speaks to that effect in many passages of Scripture, although it is sufficient at present to quote one testimony of Paul to the following effect: “Let this mind be in you which was also in Christ Jesus; who, being in the form of God, thought it not robbery to be equal with God, but made Himself of no reputation, and took upon Him the form of a servant, and was made in the likeness of men; and being found in fashion as a man, He humbled Himself, and became obedient unto death, even the death of the cross. Wherefore God also has highly exalted Him, and given Him a name which is above every name.”
Source: Against Celsus (New Advent)