Robertson on interpreting the absence of the Greek article

VIII. The Absence of the Article I do not care to use the term “omission” in connection with the article. That word implies that the article ought to be present. As has been already shown, the article is not the only means of showing that a word is definite. This luxury in language did not become indispensable. The servant never became master. There remained in the classic period many parallel phrases which were intelligible without the article. Indeed, new phrases came into use by analogy without the article. [...] Much of the modern difficulty about the absence of the Greek article is due to the effort to interpret it by the standard of the English or German article. So Winer (Winer-Thayer, p. 119) speaks of “appellatives, which as expressing definite objects should have the article”! Even Gildersleeve, in discussing the “Absence of the Article” (note the phrase, Syntax, p. 259), says that “prepositional phrases and other formulæ may dispense with the article as in the earlier language,” and he adds “but anaphora or contrast may bring back the article at any time and there is no pedantical uniformity.” Admirably said, except “dispense with” and “bring back,” dim ghosts of the old grammar.[*] Moulton cites Jo. 6:68, ῥήματα ζωῆς αἰωνίου, which should be translated ‘words of eternal life’ (as marg. of R. V.). There are indeed “few of the finer points of Greek which need more constant attention” than the absence of the article. The word may be either definite or indefinite when the article is absent. The context and history of the phrase in question must decide. The translation of the expression into English or German is not determined by the mere absence of the Greek article.

*How do you take Robertson's use of "dim"? Is it adjectival or verbal?