The following evidence illustrates how respected Trinitarian scholars have betrayed themselves concerning their own interpretation of John 17:3, "Father.... that they may know you, the only true God and Jesus Christ whom you sent."
At John 17:3, a definite article ("the") in the Greek qualifies the word "God." In other words, Jesus is referring to his Father as "THE God" and not only as "THE God" but as "the ONLY God" and not only as "the ONLY God" but as "the only TRUE God." Now carefully observe how Trinitarian scholars, when discussing their view on John 1:1, repeatedly insist that John intentionally did not use the definite article ("THE") in the Greek language at John 1:1 or he would have been excluding everyone but the Word as "God." In Greek, the word for "God" is "the god." At John 1:1, the Greek text does say, "and the word was with THE god" but it does not say in the next phrase, "and the word was THE God." It simply says, "and the word was god." These scholars insist that John intentionally left out the definite article because it would have indicated exclusivity, that only the Word was God, thereby excluding the Father from identity as "God." The Greek definite article here is the word ho.
However, these Trinitarian scholars forgot something when they were writing these words. Jesus does refer to his Father as "the only God" (John 5:44) and "the only true God." Hence, according to the insistences of these scholars, Jesus has just excluded everyone but the Father from identity as "God." Yet, these Trinitarian scholars do not accept their own words when they come to John 5:44 and John 17:3. Ratjher, they deny their own argument or they could no longer be Trinitarians.
A.T. Robertson emphatically insists that John left out the article by necessity or John would have been excluding all but the Word from identity as "God."
"And the Word was God (kai theos en ho logos). By exact and careful language John denied Sabellianism by not saying ho theos en ho logos. That would mean that all of God was expressed in ho logos and the terms would be interchangeable, each having the article. (A. T. Robertson, Word Pictures in the New Testament, vol. 5, pp. 4-5, underlined emphasis mine).
"The word with the article is then the subject, whatever the order may be. So in Jo. 1:1, theos an ho logos, the subject is perfectly clear. Cf. ho logos sarx egeneto (Jo. 1:14). It is true that ho theos an ho logos (convertible terms) would have been Sabellianism. See also ho theos agape estin (1 Jo.4:16). "God" and "love" are not convertible terms any more than "God" and "Logos" or "Logos" and "flesh." Cf. also hoi theristai angeloi eisin (Mt. 13:39), ho logos ho sos alatheia estin (Jo. 17:17), ho nomos hamartia; (Ro. 7:7). The absence of the article here is on purpose and essential to the true idea" (A. T. Robertson, A Grammar of the Greek New Testament in the Light of Historical Research, Nashville: Broadman Press, 1934, p. 767-768, underlined emphasis mine).
"A word should be said concerning the use and non-use of the article in John 1:1, where a narrow path is safely followed by the author. "The Word was God." If both God and Word were articular [if they both had the definite article "the"], they would be coextensive and equally distributed and so interchangeable [Sabellianism]. But the separate personality of the Logos is affirmed by the construction used and Sabellianism is denied. If God were articular and Logos non-articular, the affirmation would be that God was Logos, but not that the Logos was God.(A. T. Robertson, The Minister and His Greek New Testament, (Grand Rapids: Baker Book House, 1977) pp. 67-68, underlined emphasis mine).
Robertson is arguing that if John had used the definite article and said, "and the Word was (THE) God" at John 1:1, he would have been teaching Sabellianism by declaring that the Word was that one God and ONLY the Word was that one God. Essentially, he is arguing that the definite article indicates exclusivity and if one person is identified as "THE" God then nobody else can possibly be that God. Put simply, Robertson is rightly arguing that the definite article necessarily indicates exclusivity.
And here is the kicker. Robertson seems to have forgotten a simple little fact. The definite articles IS used at both John 17:3. If indeed the definite article indicates exclusivity, Robertson is sadly caught in his own dilemma. For that would also mean that Jesus excludes everyone but the Father from being God at John 17:3 because, unlike John 1:1, the definite article IS used here. In other words, we have absolute proof that scholars know very well that the definite article necessarily indicates exclusivity but they completely deny it when they come to John 17:3.
Now Robertson is not caught in this own dilemma all alone. Notice how these other scholars fall into the same trap.
C.K. Barrett also insists the presence of the definite article at John 1:1 would have indicated exclusivity and that is why John did not use it.
"The absence of the article indicates that the Word is God, but is not the only being of whom this is true; if ho theos had been written it would have implied that no divine being existed outside the second person of the Trinity."
(C.K. Barrett, The Gospel According to St. John, S.P.C.K., 1955, p.76).
And here is another one.
Dana and Mantey indicate the absence of the article is necessary so that the other persons of the Trinity are not excluded. In other words, if John had used the definite article he would have been indicating that Jesus was exclusively "God." >
The article sometimes distinguishes the subject from the predicate in a copulative sentence. In Xenophon's Anabasis, 1:4:6, emporion d' en to korion, and the place was a market, we have a parallel case to what we have in John 1:1, kai theos en ho logos, and the word was deity. The article points out the subject in these examples. Neither was the place the only market, nor was the word all of God, as it would mean if the article were also used with theos. As it stands, the other persons of the Trinity may be implied in theos.
(H. E. Dana, Julius Mantey, A Manual Grammar of the Greek New Testament, New York: The MacMillan Company, 1950, pp. 148-149).
And yet another:
F.F. Bruce also indicates that if John had used a definite article he would have been indicating that the Word was exclusively "God" by identity. Rather, Bruce says, John is referring to the nature of the Word, not the identity of the Word.
"The structure of the third clause in verse 1, theos en ho logos, demands the translation "The Word was God." Since logos has the article preceding it, it is marked out as the subject. The fact that theos is the first word after the conjunction kai (and) shows that the main emphasis of the clause lies on it. Had theos as well as logos been preceded by the article the meaning would have been that the Word was completely identical with God (the Father), which is impossible if the Word was also "with God" . (F. F. Bruce, The Gospel of John, Grand Rapids: Wm. B. Eerdmans, 1983, p. 31).
Nicoll insists that if the article was present then John would have excluded anyone but the Word from identity as God.
"The Word is distinguishable from God and yet Theos en ho logos, the Word was God, of Divine nature; not "a God," which to a Jewish ear would have been abominable; nor yet identical with all that can be called God, for then the article would have been inserted..."
(W. Robertson Nicoll, ed., The Expositor's Greek Testament, 5 vols, (Grand Rapids: Wm. B. Eerdmans Publishing Company, 1983), 1:684).
And they just keep right on going
William Barclay says the very same thing.
When the Greek uses a noun it almost always uses the definite article with it. The Greek for God is 'theos', and the definite article is 'ho'. When Greek speaks about God it does not simply say 'theos'; it says 'ho theos'. Now, when Greek does not use the definite article with a noun that noun becomes much more like an adjective; it describes the character, the quality of the person. John did not say that the Word was 'ho theos'; that would have been to say that the Word was identical with God." (Barclay, W. The Gospel of John, vol.1, The Dailey Study Bible Series, Saint Andrew Press, p. 39)
How then do any of these men explain away their desired interpretation of John 17:3? The definite article is used at John 17:3 and according to their above reasoning, this would mean that all but the Father is exclusively "the only true God." They have completely betrayed themselves. That the definite article indicates exclusivity is common sense and they are all quite right to say so when they interpret John 1:1. But what they didn't realize is their own argument necessarily professes that Jesus exclusively identifies the Father alone as the only true God at John 17:3.
And since they interpret John 20:28, "the Lord of me and the God of me," as referring to Jesus himself as "THE God" in question, their own argument would have Thomas identifying Jesus soley and exclusively as "God" at John 1:1. And again, we find them in contradiction.
Hence they insist the use of the definite article necessarily indicates exclusivity. But it is absolutely impossible to interpret John 17:3 as identifying the Father exclusively as "the only true God" and adhere to the doctrine of the Trinity at the same time because it completely rules out both the 2nd and the 3rd person as "the only true God." But when they come to John 17:3 they do necessarily insist the second and the third person of the Trinity are not excluded. So when they interpret John 1:1, they correctly insist the definite article indicates exclusivity but when they come to John 17:3 they completely deny the definite article indicates exclusivity.
And yes, it even gets worse for Trinitarians here. At John 20:17 Jesus says, "I am ascending to THE Father of me and Father of you and God of me and God of you." According to the Trinitarians, the Granville Sharp rule necessarily comes into play here and the definite articles modifies "Father of you" and "God of me" and "God of you." Here, we find that Jesus is identifying his one and only God as the Father. And here we find that Jesus' Father is also our one God. And according to the argument of these Trinitarian scholars concerning the definite article, Jesus has just declared that ONLY the Father is our God and has excluded everyone else by use of the definite article.