652 Ἐν with the subjunctive, and after a past tense εἰ with the optative, are sometimes to be translated on the chance that, in the hοpe that, if perchance; the future supposition of the ἐν or εἰ clause is a motive for the action of the leading clause:

Oὔκουν ἀτρέμʼ ἕξεις, ἤν τι καὶ χορδῆς λάβῃς won't you keep quiet then, on the chance of getting some sausage too? AR. R. 339. πέμψαντες πρέσβεις, εἴ πως πείσειαν μὴ σφῶν πέρι νεωτερίζειν μηδέν sending envoys, in hopes they might (if haply they might) induce them to make no innovations in regard to them. T. I. 58.