Read it through once

From the beginning, Virgil, like his contemporaries and immediate predecessors, was constantly adapting and using the discoveries, traditions and inventions of Greek poetry: to make use of a foreign literature in this way marks a further stage of civilisation beyond making use only of the earlier stages of one's own—though I think we can say that no poet has ever shown a finer sense of proportion than Virgil, in the uses he made of Greek and of earlier Latin poetry. It is this development of one literature, or one civilisation, in relation to another, which gives a peculiar significance to the subject of Virgil's epic.