The Arians are condemned by the Holy Spirit through the mouth of David: for they dare to limit Christ's knowledge. The passage cited by them in proof of this is by no means free from suspicion of having been corrupted. But to set this right, we must mark the word “Son.” For knowledge cannot fail Christ as Son of God, since He is Wisdom; nor the recognition of any part, for He created all things. It is not possible that He, who made the ages, cannot know the future, much less the day of judgment. Such knowledge, whether it concerns anything great or small, may not be denied to the Son, nor yet to the Holy Spirit. Lastly, various proofs are given from which we can gather that this knowledge exists in Christ.
188. Wherefore we ought to know that they who make such statements are accursed and condemned by the Holy Spirit. For whom else but the Arians in chief does the prophet condemn, seeing that they say that the Son of God knows neither times nor years. For there is nothing which God is ignorant of; and Christ, yea the most high Christ, is God, for He is “God over all.”
189. See how horrified holy David is at such men, in limiting the knowledge of the Son of God. For thus it is written: “They are not in the troubles of other men, neither will they be scourged with men; therefore their pride has laid hold on them; they are covered with their wickedness and blasphemy; their iniquity has stood forth as it were with fatness; they have passed on to the thoughts of their heart.” Truly he condemns those who think that divine things are to be regarded in the light of the thoughts of the heart. For God is not subject to arrangement or order; seeing that we do not perceive even those very things, which are common among men and often occur in the history of the human race, to turn out always after the arrangement of some stated rule, but often to happen suddenly in some secret and mysterious manner.
190. “They have thought,” he says, “and have spoken wickedness. They have spoken wickedness against the Most High. They have set their mouth against heaven.” We see then that he condemns, as guilty of wicked blasphemy, those who claim for themselves the right to arrange the heavenly secrets after the semblance of our human nature.
191. And they have said: “How has God known? And is there knowledge in the Most High?” Do not the Arians echo this daily, saying that all knowledge cannot exist in Christ? For He, they say, stated that He knew not the day nor hour. Do they not say, how did He know, while they maintain that He could not know anything but what He heard and saw, and apply by a blasphemous interpretation that which concerns the unity of the divine Nature to weaken His power?
192. It is written, they say: “But of that day and that hour knows no man, no, not the angels which are in heaven, neither the Son, but the Father only.” First of all the ancient Greek manuscripts do not contain the words, “neither the Son.” But it is not to be wondered at if they who have corrupted the sacred Scriptures, have also falsified this passage. The reason for which it seems to have been inserted is perfectly plain, so long as it is applied to unfold such blasphemy.
193. Suppose however that the Evangelist wrote thus. The name of “Son” embraces both natures. For He is also called Son of Man, so that in the ignorance attached to the assumption of our nature, He seems not to have known the day of the judgment to come. For how could the Son of God be ignorant of the day, seeing that the treasures of the wisdom and knowledge of God are hidden in Him?
194. I ask then, whether He had this knowledge by reason of His Being, or by chance? For all knowledge comes to us either through nature, or by learning. It is supplied by nature, as for instance to a horse to enable it to run, or to a fish to enable it to swim. For they do this without learning. On the other hand, it is by learning that a man is enabled to swim. For he could not do so unless he had learned. Since therefore nature enables dumb animals to do and to know what they have not learned, why should you give an opinion on the Son of God, and say whether He has knowledge by instruction or by nature? If by instruction, then He was not begotten as Wisdom, and gradually began to be perfect, but was not always so. But if He has knowledge by nature, then He was perfect in the beginning, He came forth perfect from the Father; and so needed no foreknowledge of the future.
195. He therefore was not ignorant of the days; for it does not fall to the lot of the Wisdom of God to know in part and in part to be ignorant. For how can He who made all things be ignorant of a part, since it is a less thing to know than to make. For we know many things which we cannot make, neither do we all know things in the same way but we know them in part. For a countryman knows the force of the wind and the courses of the stars in one way— the inhabitant of a city knows them in another way— and a pilot in yet a third way. But although all do not know all things, they are said to know them; but He alone knows all things in full, Who made all things. The pilot knows for how many watches Arcturus continues, what sort of a rising of Orion he will discover, but he knows nothing of the connection of the Vergiliæ and of the other stars, or of their number or names, as does He “Who numbers the multitude of stars, and calls them all by their names;” Whom indeed the power of His work cannot escape.
196. How then do you wish the Son of God to have made these things? Like a signet ring which does not feel the impression it makes? But the Father made all things in wisdom, that is, He made all things through the Son, who is the Virtue and Wisdom of God. But it befits such Wisdom as that to know both the powers and the causes of His own works. Thus the Creator of all things could not be ignorant of what He did— or be without knowledge of what He had Himself given. Therefore He knew the day which He made.
197. But you say that He knows the present and does not know the future. Though this is a foolish suggestion, yet that I may satisfy you on Scriptural grounds, learn that He made not only what is past, but also what is future, as it is written: “Who made things to come.” Elsewhere too Scripture says: “By whom also He made the ages, who is the brightness of His glory and the express Image of His Person.” Now the ages are past and present and future. How then were those made which are future, unless it is that His active power and knowledge contains within itself the number of all the ages? For just as He calls the things that are not as though they were, so has He made things future as though they were. It cannot come to pass that they should not be. Those things which He has directed to be, necessarily will be. Therefore He who has made the things that are to be, knows them in the way in which they will be.
198. If we are to believe this about the ages, much more must we believe it about the day of judgment, on the ground that the Son of God has knowledge of it, as being already made by Him. For it is written: “According to Your ordinance the day will continue.” He did not merely say “the day continues,” but even “will continue,” so that the things which are to come might be governed by His ordinance. Does He not know what He ordered? “He who planted the ear, shall He not hear? He that formed the eye shall He not see?”
Source: On the Christian Faith (De fide) (New Advent)