Plato, Resp. 353 b8

Greek Learning Greek
1

Εἶεν, ἦν δ’ ἐγώ. οὐκοῦν καὶ ἀρετὴ δοκεῖ σοι εἶναι ἑκάστῳ ᾧπερ καὶ ἔργον τι προστέτακται; ἴωμεν δὲ ἐπὶ τὰ
αὐτὰ πάλιν· ὀφθαλμῶν, φαμέν, ἔστι τι ἔργον;
Ἔστιν. (5)
Ἆρ’ οὖν καὶ ἀρετὴ ὀφθαλμῶν ἔστιν;
Καὶ ἀρετή.
Τί δέ; ὤτων ἦν τι ἔργον;
Ναί.
Οὐκοῦν καὶ ἀρετή; (10)
Καὶ ἀρετή.

Why is ἦν (which I take to be imperfect of εἰμί) rather than ἔστιν there? Thanks in advance.

2

I think imperfect is fine here. He refers back to the first example: “ἀκούσαις ἄλλῳ ἢ ὠσίν;”