296. The use of ἐπεί implies that the action is prior in time to the action of the principal clause; hence clauses with ἐπεί properly fall under the definition of the conditional clause.
A pure subjunctive after ἐπεί is found in four places, one a gnomic passage
Od. 20.86 ἐπεὶ ἂρ βλέφαρʼ ἀμφικαλύψῃ
(sleep makes men forget everything)
when it has spread over their eyelids
the other three in similes, viz. Il. 11.478, 15.363, 680. In Il. 16.453 the best MSS. give αὐτὰρ ἐπεὶ δὴ τόν γε λίπῃ ψυχή τε καὶ αἰών, πέμπειν μιν κτλ., others ἐπὴν δή. The pure subjunctive implies that the command is meant to be general in form : cp. § 292.a.
κεν or ἄν is invariably used when the principal verb is future. It is also found after a present, and even in similes.
Il. 2.474 τοὺς δʼ ὥς τʼ αἰπόλια πλατέʼ αἰγῶν αἰπόλοι ἄνδρες
ῥεῖα διακρίνωσιν, ἐπεί κε νομῷ μιγέωσιν
So ἐπεί κε(ν), Il. 7.410, 9.324, 21.575, Od. 8.554, 11.221, 24.7; and ἐπὴν, Il. 6.489, 19.223, Od. 8.553, 10.411, 11.192, 14.130, 19.206, 515. In Il. 1.168 should perhaps be read ἐπεὶ κεκάμω (instead of ἐπεί κε κάμω), and so Il. 7.5 ἐπεὶ κεκάμωσι, and Il. 17.657 ἐπεὶ ἂρ κεκάμῃσι.
Regarding ἐπεί κε(ν) in this use there is the same question as with ὅς κε (§ 283). Out of 10 instances there is only one in which the form κεν appears, viz. Il. 21.575 ἐπεί κεν ὑλαγμὸν ἀκούσῃ, and there Zenodotus read κυνυλαγμὸν, which is strongly supported by the meter (§ 367.2). Thus there is the same reason as before for supposing that κε is often merely a corruption of τε. The use of ἐπεί τε is sufficiently established in Homer (§ 332).
The form ἐπὴν is open to doubt on other grounds, which it wit be better to discuss in connection with other uses of the particle ἄν (§ 362).