John 17:3

(iii. de Tr. c. 14) And in what eternal life is, He then shews: And this is life eternal, that they might know Thee, the only true God. To know the only true God is life, but this alone does not constitute life. What else then is added? And Jesus Christ whom Thou hast sent. (iv. de Tr. c. 9) The Arians hold, that as the Father is the only true, only just, only wise God, the Son hath no communion of these attributes; for that which is proper to one, cannot be partaken of by another. And as these are as they think in the Father alone, and not in the Son, they necessarily consider the Son a false and vain God. (v. de Tr. 3) But it must be clear to every one that the reality of any thing is evidenced by its power. For that is true wheat, which when rising with grain and fenced with ears, and shaken out by the winnowing machine, and ground into corn, and baked into bread, and taken for food, fulfils the nature and function of bread. I ask then wherein the truth of Divinity is wanting to the Son, Who hath the nature and virtue of Divinity. For He so made use of the virtue of His nature, as to cause to be things which were not, and to do every thing which seemed good to Him. (ix. de Trin) Because He says, Thee the only, does He separate Himself from communion and unity with God? He doth separate Himself, but that He adds immediately, And Jesus Christ Whom Thou hast sent. For the Catholic faith confesses Christ to be true God, in that it confesses the Father to be the only true God; for natural birth did not introduce any change of nature into the Only-Begotten God.

"And this is life eternal, that they might know Thee the only true God, and Jesus Christ whom Thou hast sent." "The only true God," He saith, by way of distinction from those which are not gods; for He was about to send them to the Gentiles. But if they will not allow this, but on account of this word "only" reject the Son from being true God, in this way as they proceed they reject Him from being God at all. For He also saith, "Ye seek not the glory which is from the only God." (c. v. 44.) Well then; shall not the Son be God? But if the Son be God, and the Son of the Father who is called the Only God, it is clear that He also is true, and the Son of Him who is called the Only true God.

Why, when Paul saith, "Or I only and Barnabas" (1 Cor. ix. 6), doth he exclude Barnabas? Not at all; for the "only" is put by way of distinction from others. And, if He be not true God, how is He "Truth"? for truth far surpasses what is true. What shall we call the not being a "true" man, tell me? shall we not call it the not being a man at all? so if the Son is not true God, how is He God? And how maketh He us gods and sons, if He is not true?

(vi. de Tr. c. 9) Dismissing then the Arians, let us see if we are forced to confess, that by the words, That they may know Thee to be the only true God, He means us to understand that the Father only is the true God, in such sense as that only the Three together, Father, Son, and Holy Ghost, are to be called God? Does our Lord's testimony authorize us to say that the Father is the only true God, the Son the only true God, and the Holy Ghost the only true God, and at the same time, that the Father, Son, and Holy Ghost together, i. e. the Trinity, are not three Gods, but one true God? (Tr. c. 5) Or is not the order of the words, That they may know Thee and Jesus Christ, Whom Thou hast sent, to be the only true God? the Holy Spirit being necessarily understood, because the Spirit is only the love of the Father and the Son, consubstantial with both. If then the Son so glorifies Thee as Thou hast given Him power over all flesh, and Thou hast given Him the power, that He should give eternal life to as many as Thou hast given Him, and, This is life eternal, to know Thee, it follows that He glorifies Thee by making Thee known to all whom Thou hast given Him. Moreover, if the knowledge of God is life eternal, the more advance we make in this knowledge, the more we make in life eternal. But in life eternal we shall never die. Where then there is no death, there will then be perfect knowledge of God; there will God be most glorified, because His glory will be greatest. Glory was defined among the ancients to be fame accompanied with praise. But if man is praised in dependence on what is said of him, how will God be praised when He shall be seen? as in the Psalm, Blessed are they who dwell in Thy house: they will be alway praising Thee. (Ps. 83:4) There will be praise of God without end, where will be full knowledge of God. There then shall be heard the everlasting praise of God, for there will there be full knowledge of God, and therefore full glorifying of Him. (i. de Trin. c. viii) What He said to His servant Moses, I am that I am; (Exod. 3) this we shall contemplate in the life eternal. (iv. de Trin. c. xviii) For when sight has made our faith truth, then eternity shall take possession of and displace our mortality.

"And this," He adds, "is eternal life, that they may know Thee, the only true God, and Jesus Christ, whom Thou hast sent." The proper order of the words is, "That they may know Thee and Jesus Christ, whom Thou hast sent, as the only true God." Consequently, therefore, the Holy Spirit is also understood, because He is the Spirit of the Father and Son, as the substantial and consubstantial love of both. For the Father and Son are not two Gods, nor are the Father and Son and Holy Spirit three Gods; but the Trinity itself is the one only true God. And yet the Father is not the same as the Son, nor the Son the same as the Father, nor the Holy Spirit the same as the Father and the Son; for the Father and Son and Holy Spirit are three [persons], yet the Trinity itself is one God. If, then, the Son glorifies Thee in the same manner "as Thou hast given Him power over all flesh," and hast so given, "that He should give eternal life to all that Thou hast given Him," and "this is life eternal, that they may know Thee;" in this way, therefore, the Son glorifies Thee, that He makes Thee known to all whom Thou hast given Him. Accordingly, if the knowledge of God is eternal life, we are making the greater advances to life, in proportion as we are enlarging our growth in such a knowledge. And we shall not die in the life eternal; for then, when there shall be no death, the knowledge of God shall be perfected. Then will be effected the full effulgence of God, because then the completed glory. For glory, from which men are styled glorious, is thus defined: Glory is the widely-spread fame of any one accompanied with praise. But if a man is praised when the fame regarding him is believed, how will God be praised when He Himself shall be seen? Hence it is said in Scripture, "Blessed are they that dwell in Thy house; they will be praising Thee for ever and ever." There will God's praise continue without end, where there shall be the full knowledge of God; and because the full knowledge, therefore also the complete effulgence or glorification.