Gonzalez Lodge, Commentary on Plato: Gorgias

ἀναγκαῖαι . . . πολεῖσθαι: the personal construction proceeds from the ‘prolepsis’ of the subject of the inf.,—a common occurrence with δίκαιος and δῆλος. The real subject of the infinitive is then ἐνίας τῶν ἀποκρίσεων. Of this construction Plato affords other examples. Cf. Meno 79 d ἀπόκρισιν τὴν διὰ τῶν ἔτι ζητουμένων . . . ἐπιχειροῦσαν ἀποκρίνεσθαι, Phaedo 92 d τοῖς διὰ τῶν εἰκότων τὰς ἀποδείξεις ποιουμένοις λόγοις. In translation the adj. must be made neuter, or a circumlocution must be used. “There are certain answers in which it is necessary for one to deliver himself more at length.” See H. 944 a; Rid. § 230.

διὰ βραχυτάτων: simply a circumlocution for the superlative adv., and accordingly const. with ὡς acc. to the usual rule. Kr. 49, 10, 1; H. 651 a. In the next sent., ἐν seems to have much the same force as διά here.

μηδένα ἂν . . . εἰπεῖν: the use of μή here is not to be considered as due to indir. disc. which would require οὐ, but as being in an inf. clause which is in apposition with ἕν.

ῥητορικῆς γὰρ κτἑ.: γάρ introduces the reason for the question which is announced in the challenging phrase, φέρε δή. Hence the position of the causal clause.