Sorry, I think I may be abusing this forum by prolonging this closed discussion. But I'd like to ask more questions, in case anyone is still following this... So far the feedback has been very helpful.
Another reference that I keep encountering is to the fact that there exist other 'tenseless' languages (besides Greek), which reportedly do not semantically encode temporal reference in their verbal systems at all. I suppose these are "purely aspecual" languages?
What language(s) exactly are being referred to? Are they Indo-European? Are they in any way releated to the Hellenic language branch? What's their relevance for comparison to Greek?
In the end of Campbell's book, he seems to draw the comparison in reference to a study on Aboriginal Australian languages. But I'm not sure how that's relevant...
He also states the following in regards to the supposed trend of languages to transition from "a spacial way of thinking to a temporal way of thinking":
Such is the case with Greek. Most scholars would agree that the verbal system of Greek was originally spatial, back in its earliest stages of development. And, of course, the Greek verbal system is now temporal - Modern Greek has tenses. The question, however, is this: When did the verbal system cease to be primarily spatial and develop its temporal characteristics? While most scholars see the verbal system as consisting of tenses as early as Homeric Greek, and certainly by the time of Attic Greek, I have argued that the verbal system is still primarily spatial at this time and indeed continues to be so through the Koine period.
There is, nevertheless, evidence that the development from spatial to temporal meaning is taking place by this time. For example, the existence of the future tense-form, which is a real tense, is the first verb form that has a consistent temporal reference. It is a genuine tense, with its core meaning concerned with the expression of time. The existence of a real tense alongside other verb forms that are not regarded as tenses at the semantic level does not constitute a problem for my analysis, nor is it inconsistent. It is no accident that the only real tense within the indicative mood is also the last of the ancient tense-forms to develop. It is thus evidence that the shift from spatial to temporal encoding is taking place in the diachronic development of the language. Eventually, the entire indicative system will consist of tenses, and the future tense is the first exponent of this situation.
There doesn't seem to be a citation for the above. Is this baseless speculation? Is it question-begging conjecture? If the invention of the future tense-form marks the beginning of the transition from spacial to temporal reference, and Modern Greek marks the end point as being fully temporal (even though Modern Greek is largely aspectual), how would he determine that further development of tense in the indicative mood (i.e. in the aorist indicative) only made headway AFTER the Hellenistic period?
I assume that when someone throws around the phrase, "Most scholars believe X...", the name(s) of at least one or two scholars could be tracked down to shore up the position. I'd really like to read some more on this diachronic development of tense in Greek. But I'm kind of stuck without a citation or bibliography in Campbell's book.