ἄν may be omitted in the apodosis of an unreal condition when the apodosis consists of an imperfect indicative denoting unfulfilled obligation, possibility, or propriety. Such are the impersonal expressions ἔδει, χρῆν, ἐξῆν, εἰκὸς ἦν, καλὸν ἦν, etc., with the infinitive, the action of which is (usually) not realized.
εἰ ταῦτα ἐποίει, ἔδει (ἐξῆν) αἰτιᾶσθαι αὐτόν
εἰ ταῦτα ἐποίησε, ἔδει (ἐξῆν) αἰτιά_σασθαι (or αἰτιᾶσθαι) αὐτόν
a. Here ἔδει and ἐξῆν are auxiliaries and the emphasis falls on the infinitive. The impersonal verb has the effect of a modifying adverb denoting obligation, possibility, or propriety: thus ἔδει αἰτιᾶσθαι αὐτόν is virtually equivalent to δικαίως ἂν ᾐτιᾶτο, and εἰκὸς ἦν αἰτιά_σασθαι αὐτόν to εἰκότως ἂν ᾐτιά_θη
b. ἔδει, χρῆν, etc., may be used in simple sentences ( cross1774 ff.) without any protasis either expressed or implied. But a protasis may often be supplied in thought.2314
The present infinitive generally expresses what would necessarily, possibly, or properly be done now. The aorist, and sometimes the present, infinitive expresses what would necessarily, possibly, or properly have been done in the past.
a. Present infinitive of present time:
χρῆν δήπου, εἴτε τινὲς αὐτῶν πρεσβύτεροι γενόμενοι ἔγνωσαν ὅτι νέοις οὖσιν αὐτοῖς ἐγὼ κακὸν πώποτέ τι ξυνεβούλευσα, νυ_νὶ_ αὐτοὺς ἀναβαίνοντας ἐμοῦ κατηγορεῖν
b. Present infinitive of past time: εἴ τινα (προῖκα) ἐδίδου, εἰκὸς ἦν καὶ τὴν δοθεῖσαν ὑπὸ τῶν παραγενέσθαι φασκόντων μαρτυρεῖσθαι
c. Aorist infinitive of past time: εἰ ἐβούλετο δίκαιος εἶναι περὶ τοὺς παῖδας, ἐξῆν αὐτῷ . . . μισθῶσαι τὸν οἶκον
With the same impersonal expressions, ἄν is regularly used when the obligation, possibility, or propriety, and not the action of the verb dependent on ἔδει, etc., is denied. Here the main force of the apodosis falls on the necessity, possibility, or propriety of the act.
εἰ ταῦτα ἐποίει, ἔδει (ἐξῆν) ἂν αἰτιᾶσθαι αὐτόν
With ἄν, it is implied that the obligation does (or did) not exist; without ἄν, it is implied that the action of the dependent infinitive is (or was)
not realized. Thus the first sentence in 2315, without ἄν, would mean: if he were doing this (as he is not), one ought to blame him; but, as the case now stands, one does not blame him.2317 2318
ἄν is regularly omitted in an apodosis formed by the imperfect of μέλλω and the infinitive (usually future) to denote an unfulfilled past intention or expectation (cp. the Lat. future participle with eram or
ἦ μάλα δὴ Ἀγαμέμνονος . . . φθί_σεσθαι κακὸν οἶτον ἐνὶ μεγάροισιν ἔμελλον, εἰ μὴ . . . ἔειπες
ἄν may be omitted with the aorist of κινδυ_νεύω
εἰ μὴ δρόμῳ μόλις ἐξεφύγομεν εἰς Δελφούς, ἐκινδυ_νεύσαμεν ἀπολέσθαι
εἰ μέντοι τότε πλείους συνελέγησαν, ἐκινδύ_νευσεν ἂν διαφθαρῆναι πολὺ τοῦ στρατεύματος
Some expressions containing a secondary tense of the indicative without ἄν, and not followed by a dependent infinitive, are virtually equivalent to the apodosis of an unreal condition.
τούτῳ δ' ει' μὴ ὡμολόγουν ἃ οὗτος ἐβούλετο, οὐδεμιᾷ ζημίᾳ ἔνοχος ἦν
a. Imperfects (not impersonal) without ἄν are often emended, as ᾐσχυ_νόμην μέντοι (some editors μέντἄν), εἰ ὑπὸ πολεμίου γε ὄντος ἐξηπατήθην
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].