In the first quote we see that the redeemed heathen will confess Jesus as the only true God. In the second quote we see that if we don’t know God the Father or Jesus Christ we cannot commune with the only true God: they both are the only true God.

What does this mean?

So what exactly did Christ mean by saying that eternal life is through knowing Thee, the only true God and Jesus Christ whom thou has sent? The key word is “sent”. How can we possibly know God unless Christ came to this earth, became a man and revealed God to us? How could Christ have revealed the only true God to us, unless He also was the only true God? Jesus said, “he that hath seen me hath seen the Father” (John 14:9). If Jesus is not the only true God, how can this be true?

Ellen White sheds a lot of light on this verse.

“This is life eternal, that they might know Thee, the only true God, and Jesus Christ, whom Thou has sent.” [John 17:23-26, quoted.] What breadth and depth and height these words reveal. Christ came to this earth to reveal the Father, to place Him in a correct light before men. { 18MR 331.4 }

“The existing religion left man without God and without hope in the world. But the Sun of Righteousness shines forth into the midnight darkness of superstition and error, and rolls back the cloud, and presents himself as the one in whom dwelleth all the fullness of the Godhead bodily, as the exact representation of the Father. This is his message to the world: “And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent.” { ST June 27, 1892, par. 4 }

“And this is life eternal, that they might know Thee the only true God, and Jesus Christ, whom Thou hast sent” [John 17:3]. The eternal Word became flesh and dwelt among us. This theme will quench unbelief…” —Manuscript 16, 1890. { VSS 315.2} { ST October 17, 1892, par. 1 }

So this phrase means that Christ came to this earth to reveal the Father. It is nothing to do with putting a distinction between the Father and Christ. In fact Ellen White saw this verse are meaning that BOTH the Father and Son were the only true God: consider this quote:

“The Saviour has said, “He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him” He says again, “And this is life eternal, that they might know thee, the only true God, and Jesus Christ whom thou hast sent.” Mohammedanism has its converts in many lands, and its advocates deny the divinity of Christ. Shall this faith be propagated, and the advocates of truth fail to manifest intense zeal to overthrow the error, and teach men of the pre-existence of the only Saviour of the world? O how we need men who will search and believe the word of God, who will present Jesus to the world in his divine and human nature, declaring with power and in demonstration of the Spirit, that “there is none other name under heaven given among men, whereby we must be saved.” O how we need believers who will now present Christ in life and character, who will hold him up before the world as the brightness of the Father’s glory, proclaiming that God is love! { HM September 1, 1892, Art. A, par. 4 }

In fact Ellen White often uses this verse in reference to knowing Christ, without even mentioning the Father:

“In his prayer to the Father, Christ said, “This is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent.” We must learn of Christ. We must know what he is to those he has ransomed.” { RH April 24, 1900, par. 6 }

“We are to grow in grace and in the knowledge of our Lord and Saviour Jesus Christ. Jesus said, “This is life eternal, that they might know thee, the only true God, and Jesus Christ whom thou has sent.” { ST March 28, 1892, Art. A, par. 4 }

“Through the knowledge of Christ is life eternal. In His prayer Jesus says, “And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent.” { PCP 45.4 }

The one thing for us to know is Christ, “the Way, the Truth, and the Life.” “This is life eternal,” He said, “that they might know Thee the only true God, and Jesus Christ, whom Thou hast sent.” { ST January 6, 1898, par. 9 }

“In Him was life, original, unborrowed, underived. This life is not inherent in man. He can possess it only through Christ. He cannot earn it; it is given him as a free gift if he will believe in Christ as His personal Saviour. “This is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent” ( John 17:3). This is the open fountain of life for the world.” { 1SM 296.2}

“This is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent” ( John 17:3). By beholding Christ, you will become changed, until you will hate your former pride, your former vanity and self-esteem, your self-righteousness and unbelief. { 1SM 388.1}

This last one give us the answer:

“This is life eternal,” Christ declared, “that they might know Thee the only true God, and Jesus Christ, whom Thou hast sent.” These words mean much. It is only by knowing Christ that we can know God. { ST January 27, 1898, par. 8 }

The reason why Jesus said “This is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent” is because the only way to know the only true God in heaven is by knowing Christ, who is also the only true God in human form. He revealed God to us. The only true God became flesh and walked among us. While as a human being on this earth, He was the personification of the only true God:

“By rejecting the Son of God, the personification of the only true God, who possessed goodness, mercy, and untiring love, whose heart was ever touched with human woe, and choosing a murderer in his stead, the Jews showed what human nature can and will do when the restraining power of the Spirit of God is removed, and men are under the control of the apostate. Those who choose Satan as their ruler will reveal the spirit of their chosen master.” { RH January 30, 1900, Art. A, par. 6 }

Please note: by rejecting Chris, they rejected the Father, the Son and the Holy Spirit: All three are the only true God.

And finally:

“One interest will prevail, one subject will swallow up all others, Christ our Righteousness. This is life eternal, “That they might know thee, the only true God, and Jesus Christ whom thou hast sent.” “Thus saith the Lord, Let not the wise man glory in his wisdom, neither let the mighty man glory in his might, let not the rich man glory in his riches; but let him that glorieth, glory in this, that he understandeth and knoweth me, that I am the Lord which exerciseth loving kindness, judgment, and righteousness in the earth; for in these things I delight, saith the Lord.” { PC 342.2 }

Christ is our gateway to God, because He is God and humanity combined.