καὶ νῦν δὴ σφόδρα διανοηθέντες καὶ ἱκανῶς διαλογισάμενοι, μήτ᾽ εἴς τινας ὠφελίας ἐπιστημῶν βλέψαντες μήτε τινὰς εὐδοκιμίας, ἀλλ᾽ εἴ τις πέφυκε τῆς ψυχῆς ἡμῶν δύναμις ἐρᾶν τε τοῦ ἀληθοῦς καὶ πάντα ἕνεκα τούτου πράττειν, ταύτην εἴπωμεν
why is the negative μή? is it either because it depends on the hortative subjunctive εἴπωμεν or because it is a reason/condition for εἴπωμεν?
probably μη is used because it depends upon a hortative subjunctive.