ἀδιανοήτως

From LSJ

εἰ γάρ κεν καὶ σμικρὸν ἐπὶ σμικρῷ καταθεῖο καὶ θαμὰ τοῦτ᾽ ἔρδοις, τάχα κεν μέγα καὶ τὸ γένοιτο → for if you add only a little to a little and do this often, soon that little will become great (Hesiod W&D, 361-362)

Source

Russian (Dvoretsky)

ἀδιανοήτως: неразумно (ἀλογίστως καὶ ἀ. Plat.).

Spanish

sin reflexionar, tontamente