A. T. Robertson and Dana-Mantey point out that the article in ancient Greek is not simply a haphazard use of speech:
"The vital thing is to see the matter from the Greek point of view and find the reason for the use of the article" (Robertson 756).
"It may be observed that in Homer 'the article marks contrast and not mere definiteness' " (Ibid., 755).
"The articular construction emphasizes identity; the anarthrous construction emphasizes character . . . It is certain that one engaged in exegesis cannot afford to disregard the article. The New Testament justifies the observation of Bultmann that 'the use of the article has everywhere its positive reason' " (D-M 140).
"Surely when Robertson says that QEOS, as to the article, 'is treated like a proper name and may have it or not have it"'(R. 761), he does not mean to intimate that the presence or absence of the article with QEOS has no special significance. We construe him to mean that there is no definite rule governing the use of the article with QEOS,
so that sometimes the writer's viewpoint is difficult to detect, which is entirely true" (D-M 140).
"A qualitative noun is a noun (in Greek always anarthrous) whose function in the sentence is not primarily or solely to designate by assignment to a class but to describe by the attribution of quality, i.e., of the quality or qualities that are the marks of the class designated by the noun. The effect is to ascribe to that which is modified the characteristics or qualities of a class and not merely to ascribe to it membership in that class. It is connotive rather than the denotive sense that emerges. In the sentence 'Frederick is a prince' the word 'prince' is either designative, marking Frederick as a member of a class, a son of a monarch, or qualitative, describing Frederick as the possessor of the superior character presumed to distinguish the son of a king" (Arthur W. Slaten (Qualitative Nouns in the Pauline Epistles and Their Translation in the Revised Version) [Chicago: Chicago UP, 1918], p. 5-7).
"In vs. 1c the Johannine hymn is bordering on the usage of 'God' for the Son, but by omitting the article it avoids any suggestion of personal identification of the Word with the Father. And for Gentile readers the line also avoids any suggestion that the Word was a second God in any Hellenistic sense" (Raymond Brown, Anchor Bible Commentary, Vol. 29, John I-XII, page 24).
"There is a further consideration, however. We have mentioned the suggestion by the Catholic scholar De Ausejo that the Word throughout the Prologue means the Word-become-flesh and that the whole hymn refers to Jesus Christ. If this is so, then perhaps there is justification for seeing in the use of the anarthrous QEOS something more humble than the use of hO QEOS for the Father. It is Jesus Christ who says in John 14:28, 'The Father is greater than I,' and who in [John] 17:3 speaks of the Father as 'the only true God.' The recognition of a humble position for Jesus Christ in relation to the Father is not strange to early Christian hymns, for Philippians 2:6, 7 speaks of Jesus as emptying himself and not clinging to the form of God" (Ibid., 25)