Tractates on the Gospel of John

⁶ If we have understood this, thanks be to God; but if any has not sufficiently understood, man has done as far as he could: as for the rest, let him see whence he may hope to understand. As laborers outside, we can plant and water; but it is of God to give the increase. “My doctrine,” says He, “is not mine, but His that sent me.” Let him who says he has not yet understood hear counsel. For since it was a great and profound matter that had been spoken, the Lord Christ Himself did certainly see that all would not understand this so profound a matter, and He gave counsel in the sequel.

Do you wish to understand? Believe. For God has said by the prophet: “Unless you believe, you shall not understand.” To the same purpose what the Lord here also added as He went on— “If any man is willing to do His will, he shall know concerning the doctrine, whether it be of God, or whether I speak from myself.” What is the meaning of this, “If any man be willing to do His will”? But I had said, if any man believe; and I gave this counsel: If you have not understood, said I, believe.

For understanding is the reward of faith. Therefore do not seek to understand in order to believe, but believe that you may understand; since, “except ye believe, you shall not understand.” Therefore when I would counsel the obedience of believing toward the possibility of understanding, and say that our Lord Jesus Christ has added this very thing in the following sentence, we find Him to have said, “If any man be willing to do His will, he shall know of the doctrine.” What is “he shall know”?

It is the same thing as “he shall understand.” But what is “If any man be willing to do His will”? It is the same thing as to believe. All men indeed perceive that “shall know” is the same thing as “shall understand:” but that the saying, “If any man be willing to do His will,” refers to believing, all do not perceive; to perceive this more accurately, we need the Lord Himself for expounder, to show us whether the doing of the Father's will does in reality refer to believing. But who does not know that this is to do the will of God, to work the work of God; that is, to work that work which is pleasing to Him?

But the Lord Himself says openly in another place: “This is the work of God, that you believe in Him whom He has sent.” “That ye believe in Him,” not, that you believe Him. But if you believe on Him, you believe Him; yet he that believes Him does not necessarily believe on Him. For even the devils believed Him, but they did not believe in Him. Again, moreover, of His apostles we can say, we believe Paul; but not, we believe in Paul: we believe Peter; but not, we believe in Peter.

For, “to him that believes in Him that justifies the ungodly, his faith is counted unto him for righteousness.” What then is “to believe in Him”? By believing to love Him, by believing to esteem highly, by believing to go into Him and to be incorporated in His members. It is faith itself then that God exacts from us: and He finds not that which He exacts, unless He has bestowed what He may find. What faith, but that which the apostle has most amply defined in another place, saying, “Neither circumcision avails anything, nor uncircumcision, but faith that works by love?” Not any faith of what kind soever, but “faith that works by love:” let this faith be in you, and you shall understand concerning the doctrine.

What indeed shall you understand? That “this doctrine is not mine, but His that sent me;” that is, you shall understand that Christ the Son of God, who is the doctrine of the Father, is not from Himself, but is the Son of the Father.