τοῦτο μὲν ἄρα μὴ ἀποδεχώμεθα, ὃς ἂν λέγῃ συλλαβὴν μὲν γνωστὸν καὶ ῥητόν, στοιχεῖον δὲ τοὐναντίον.
therefore , let us not accept this, whoever says that the syllable is knowable and expressable, but the letter is opposite to this.
there is no grammatical connection between the clauses, therefore this juxtaposition is so jarring.