In an unpublished and not-fully-edited set of short essays on Plato’s Understanding of Philosophy (the “P.U.P. Papers”), my late friend and former professor John Bremer wrote that
 The distinction between ‘being’ and ‘becoming’ –so explicit in Plato’s dialogues– originated in the need to go beyond a discourse of endless Homeric ‘happenings’, all of which were conditioned by time, a discourse of ‘becoming’, and to have a discourse of ‘being’ in which analytic statements could be made as eternally true or false — what we now regard as knowledge par excellence. A statement such as ‘The sum of the angles of a triangle equals two right angles’ is not time-conditioned, it is not a happening or an event, but is true for all time. And for all triangles. And so the many triangles are made, as it were, into one…It simply IS.
Such statements cannot be made in Homeric Greek — but they constitute what is today regarded as knowledge, as statements of what is eternally true. On the contrary, Homeric heroes are not constant — sometimes they are bold and courageous, and at other times they may be craven and cowardly; each hero is a ‘many’ — this way at one time, that way at another.
The endless Homeric happenings or events are separated from one another, each one sharply distinguished from its antecedent and its successor, each one taking place in time. The relation each has with its neighbors is, as has been said, paratactic, that is, they are only connected chronologically. First, one happened, then another happened…They are ‘many’ and Homeric language and thought cannot ever make them ‘one’, that is, cannot integrate them into a system, for example, of cause and effect or make them a ‘universal’.
[…] [In Homeric Greek, the verb “to be” can be used as a copular (e.g., Plato is an Athenian), but not to predicate existence (e.g., the sum of the angles of a triangle is equal to two right angles). It becomes impossible to talk about universals such as triangles, as a result.] And if there is no way of saying it, there is no way of thinking it.
This content of the tribal memory is precisely what Plato calls ‘opinion’ (δόξα) and it represents the limits within which an oral culture can express itself, and the meaning that ‘thinking’, ‘knowledge’, and ‘being’ can have. What was needed was a mode of speech –or, rather, of language spoken or written– that would express ‘being’ as well as ‘becoming’, that could make statements without time-conditioning. The diagram described at the end of Republic Book 6, the Divided Line […], illustrates both the Homeric view that Plato and his contemporaries inherited, and also what Plato added to that view to make what we call knowledge possible. The words ‘knowing’ and ‘being’ are used but often ambiguously — according to the Line there are four kinds of knowledge and correspondingly four kinds of being, but sometimes (at least in English) ‘knowledge’ and ‘being’ can be used to signify all kinds or only the highest kinds. They are often ambiguous.
 […] To summarize and formalize what has been said in the preceding PUP Papers: In an oral culture such as the Homeric one, a culture essentially without writing, the preservation and continuation of the culture itself, kits paideia, depends on the use of spoken words which report how things are done, how they have always been done, all the social and political mechanisms by which the culture conducts its business — which essentially is the culture. This report depends, in the first place, on the singer who can ‘sing’ what it has to say, and, in the second place, on memory — the memory of the singer and of his audience. […]
 […] [This requires that the audience remembers its culture, or that, if they should forget part of it, the singer can summon it forth from the oblivion of his memory into the actuality of performing it.] The stable element in this whole culture would seem to be the words of Homer or some other poet, but these words were only available through the memory of the citizens, and, ultimately, of the singer. The memory of the individual or of the singer brings into being, as it were, what is required, and when used it falls back into oblivion, into forgetfulness. It, like the paideia of which it is the encyclopedia, is time-conditioned and the remembered account passes across the ears of its audience like a Heraklitean flux.
The introduction of writing changed this picture and changed it dramatically. […the singer degenerated from a significant cultural authority into a mere entertainer…] The text of Homer or anyone else, once written, assumed a life of its own and was available for inspection and consultation. It was, of course, inspected by the eye –not the ear as with the singer’s version– and it did not move but remained static for as long as anyone wished — and longer. Its existence was not fleeting but allowed certain intellectual operations to be carried out which were impossible with the declaimed version.
First, a passage could be read over and over again, whereas the singer could not be stopped in the midst of his declamation and be asked to repeat a passage. Second, this made it possible to think about a given passage, to consider it, to reflect upon it. Third, part of the reflection process could and did permit evaluation and consideration of alternatives. Fourth, a passage about, say, feasting, could be examined side-by-side with other passages on the same subject, which would encourage comparison — and evaluation. Fifth, it became possible to rearrange the Homeric words so that, for example, all the passages relating, say, to armor could be collected together, could be unified. Obviously, any of those passages, if they contained references to metallic composition, could in addition be collected under such a heading. The written text could be organized in many ways simultaneously. While the sung or declaimed version was controlled by time –existing only in the process of singing– the written version was indifferent to time; it could be examined, then put aside, and then taken up again. It was controlled by space, as it were, not by time.
In short, the existence of a written text made possible and encouraged certain intellectual operations that could not even be conceived under an oral-based regime, let alone carried out. [PUP Papers 28, 29, 30]
John was an educator, and so his concern with the implications of the Homeric or Platonic models of training/education (paideia) are here on full display. There are technological and social conditions that must be met before certain things can be thought; what is the effect of these upon culture, education, knowledge?
In passing, I should note that the Greek word that is here used for opinion. “δόξα”, also means “glory”; it seems that this word is also used for the “appearances” of things. Speculating on the origins of these manifold senses in one word, I would suggest that the declaiming of epic poems is about singing the “glory” of a hero, which is, in philosophical terms, just a string of happenings, of “and then, and then, and then”, just a set of appearances, and so, at the lowest strand of knowledge — opinion.
Regarding how these considerations bear upon the question of universals and knowledge, I have mentioned this before in this post, sections IV and VI.
As a postscript, this distinction between the faculties of sight and hearing, and the respective permanence or fluidity of their objects, is also to be found in the essays of Hans Jonas’ The Phenomenon of Life. To oversimplify, Jonas sides with hearing.