Such a rule of difference is easy to be traced.
For example. In the Catalogue[614] and elsewhere, if in the course of the action he refers to the soldiers who proceeded from the country afterwards called Bœotia, he calls them Βοιωτοί. But where Agamemnon has, or rather makes, occasion to tell a story of the same people acting in prior history, he calls them, not Βοιωτοὶ, but once Καδμεῖοι, and once by the equivalent name Καδμειῶνες[615]. The tale is an account of the mission of Tydeus from Thebes to Mycenæ, in company with Polynices, which had occurred under the Pelopid dynasty.
In this story it appears, that Tydeus and Polynices, first obtained a promise of the help they wanted; but that, after they had departed, there was a change of resolution. Hence messengers were sent to acquaint Tydeus, and apparently to recall the force. The expression is (Il. iv. 384),
ἔνθ’ αὖτ’ ἀγγελίην ἐπὶ Τύῃ στεῖλαν Ἀχαιοί.
An allusion to this occurrence is again put into the mouth of Minerva in Il. v. 800-7. The resemblance in the names used is so precise as to be almost precisian. Again, the Mycenians are named once, and named as Ἀχαιοί. Again, the Thebans are named twice, and once it is as Καδμεῖοι, once as Καδμείωνες.
Proofs of the distinctive use.
These two instances fortify one another to such a degree by their concurrence, that, as I would submit, they would, even if they stood alone, amount to a demonstration that Homer had regard to the times and circumstances under which the several races prevailed, in those passages of his work which refer to particular incidents of prior history, personal and local. But there is no lack of other evidence.
First, we have other pieces of prior history, which affect the same portion of Greece. The first of these probably preceded the Troica by only two, or, at the utmost, two and a half generations. It is the account of the birth of Eurystheus, given by Agamemnon himself in the Nineteenth Book. The scene of it is described as Ἄργος Ἀχαιïκόν. He calls it indeed by the name, which it still bore at the time when he spoke, and which was understood by the hearers, for it remained the same country as it had been in former times. But the same people, who in the time of Tydeus, living under the Pelopids, were Ἀχαιοὶ, in the time of Eurystheus, and therefore before the predominance of the Pelopids, are described as Ἀργεῖοι. In Il. xix. 122, Juno thus speaks of the birth of Eurystheus
ἤδη ἀνὴρ γέγον’ ἐσθλὸς, ὃς Ἀργείοισιν ἀνάξει.
And again, v. 124, the same term is used.