σὺ ἄρα κτἑ.: Polus cannot tear himself away from his fast-rooted ideas. Hence all teaching is vain.
ὦ μακάριε: has somewhat of an ironical coloring. The nearest English equivalent is the half serious “Oh, you awful fellow!”—
ἐμοῦ δὴ λέγοντος: as an offset to Polus' words ἀλλ᾽ ἔγωγε τοῦτο λέγω. “Let us have, then, argument for argument.” The gen. may depend on ἐπιλαβοῦ, as in 506 b, but it is more likely gen. abs. See on ἀντιλαμβάνεσθαι, 506 a, and Symp. 214 e ἐάν τι μὴ ἀληθὲς λέγω, μεταξὺ ἐπιλαβοῦ, ἂν βούλῃ, καὶ εἰπὲ ὅτι τοῦτο ψεύδομαι. The original meaning is made clear by Prot. 329 a τὰ χαλκεῖα πληγέντα μακρὸν ἠχεῖ καὶ ἀποτείνει, ἐὰν μὴ ἐπιλάβηταί τις (unless one takes hold of it).
τῳ λόγῳ: instrumental dat., “with your argument.”