http://www.perseus.tufts.edu/hopper/tex ... 99.04.00071008. Plural of Modesty.—A speaker in referring to himself may use the first person plural as a modest form of statement. In prose, of an author: ““ἔννοιά ποθ᾽ ἡμῖν ἐγένετο” the reflection once occurred to me” X. C. 1.1.1. In tragedy, often with interchange of plural and singular: εἰ κωλυόμεσθα μὴ μαθεῖν ἃ βούλομαι if I (Creusa) am prevented from learning what I wish E. Ion 391, ““ἱκετεύομεν ἀμφὶ σὰν γενειάδα . . . προσπίτνων” I entreat thee, as I grasp thy beard” E. H. F. 1206. See 1009.
Herodotus makes fairly often statements where he says something like "as far as we know...". Does this qualify for a plural of modesty, or is it rather some way to say "as is we [Greeks] generally know"? Example, Hdt 1.6.3:
οὗτος ὁ Κροῖσος βαρβάρων πρῶτος τῶν ἡμεῖς ἴδμεν τοὺς μὲν κατεστρέψατο Ἑλλήνων ἐς φόρου ἀπαγωγήν, τοὺς δὲ φίλους προσεποιήσατο. κατεστρέψατο μὲν Ἴωνάς τε καὶ Αἰολέας καὶ Δωριέας τοὺς ἐν τῇ Ἀσίῃ, φίλους δὲ προσεποιήσατο Λακεδαιμονίους.