John 14:5

(Hom. lxxiii. 2) If the Jews, who wished to be separated from Christ, asked whither He was going, much more would the disciples, who wished never to be separated from Him, be anxious to know it. So with much love, and, at the same time, fear, they proceed to ask: Thomas saith unto Him, Lord, we know not whither Thou goest; and how can we know the way?

(Tr. lxix. 1) Our Lord had said that they knew both, Thomas says that they knew neither. Our Lord cannot lie; they knew not that they did know. Our Lord proves that they did: Jesus saith unto Him, I am the way, the truth, and the life.

We have now the opportunity, dearly beloved, as far as we can, of understanding the earlier words of the Lord from the later, and His previous statements by those that follow, in what you have heard was His answer to the question of the Apostle Thomas. For when the Lord was speaking above of the mansions, of which He both said that they already were in His Father's house, and that He was going to prepare them; where we understood that those mansions already existed in predestination, and are also being prepared through the purifying by faith of the hearts of those who are hereafter to inhabit them, seeing that they themselves are the very house of God; and what else is it to dwell in God's house than to be in the number of His people, since His people are at the same time in God, and God in them? To make this preparation the Lord departed, that by believing in Him, though no longer visible, the mansion, whose outward form is always hid in the future, may now by faith be prepared: for this reason, therefore, He had said, "And if I go away and prepare a place for you, I will come again, and receive you unto myself; that where I am, there ye may be also. And whither I go ye know, and the way ye know." In reply to this "Thomas saith unto Him, Lord, we know not whither Thou goest: and how can we know the way?" Both of these the Lord had said that they knew; both of them this other declares that he does not know, to wit, the place to which, and the way whereby, He is going. But he does not know that he is speaking falsely; they knew, therefore, and did not know that they knew. He will convince them that they already know what they imagine themselves still to be ignorant of. "Jesus saith unto him, I am the way, and the truth, and the life." What, brethren, does He mean? See, we have just heard the disciple asking, and the Master instructing, and we do not yet, even after His voice has sounded in our ears, apprehend the thought that lies hid in His words. But what is it we cannot apprehend? Could His apostles, with whom He was talking, have said to Him, We do not know Thee? Accordingly, if they knew Him, and He Himself is the way, they knew the way; if they knew Him who is Himself the truth, they knew the truth; if they knew Him who is also the life, they knew the life. Thus, you see, they were convinced that they knew what they knew not that they knew. What is it, then, that we also have not apprehended in this discourse? What else, think you, brethren, but just that He said, "And whither I go ye know, and the way ye know"? And here we have discovered that they knew the way, because they knew Him who is the way: the way is that by which we go; but is the way the place also to which we go? And yet each of these He said that they knew, both whither He was going, and the way. There was need, therefore, for His saying, "I am the way," in order to show those who knew Him that they knew the way, which they thought themselves ignorant of; but what need was there for His saying, "I am the way, and the truth, and the life," when, after knowing the way by which He went, they had still to learn whither He was going, but just because it was to the truth and to the life He was going? By Himself, therefore, He was going to Himself. And whither go we, but to Him, and by what way go we, but by Him? He, therefore, went to Himself by Himself, and we by Him to Him; yea, likewise both He and we go thus to the Father. For He says also in another place of Himself, "I go to the Father;" and here on our account He says, "No man cometh unto the Father but by me." And in this way, He goeth by Himself both to Himself and to the Father, and we by Him both to Him and to the Father.

How can our Lord say, If ye had known Me, ye should have known My Father also; when He has just said, Whither I go ye know, and the way ye know? We must suppose that some of them knew, and others not: among the latter, Thomas.