James Adam, The Republic of Plato

Instead of βλάψειν, the best MSS read βλάψει. If βλάψει is retained, the subject must be either (1) τις or ὁ ἐθέλων πημαίνειν supplied out of πημῆναι ἐθέλῃ, or (2) the prophet consulted. The latter alternative gives the right sense, but the change from the singular to the plural (in πείθοντες) is very harsh. If we adopt the first alternative (to which J. and C. incline), we must regard the clause ἐάν τέ τινα— βλάψει as semi-parenthetical, and connect πείθοντες with ἀγύρται δὲ καὶ μάντεις at the beginning of the sentence. Such a solution is not less harsh than (2). βλάψει must, I think, be pronounced corrupt. Muretus read βλάψαι, depending, like ἀκεῖσθαι, on δύναμις; but βλάψαι is not likely to have been corrupted into βλάψει, nor is it clear why the aorist should take the place of the present (as in ἀκεῖσθαι). Reading βλάψειν, we might perhaps regard the construction as one of the rare cases in which δύναμις and the like are followed by a future infinitive: see Jebb's Soph. Phil. p. 252, Kühner Gr. Gr. II p. 164, and cf. Phaed. 73 A οὐκ ἂν οἷοί τ᾽ ἦσαν τοῦτο ποιήσειν (so the Bodleian MS). There is still however a serious difficulty in the collocation of the present ἀκεῖσθαι with the future βλάψειν. The explanation given by Schneider in his Additamenta is linguistically unassailable and gives an excellent sense. For the common confusion of -ει and -ειν see Introd. § 5.