James Adam, The Republic of Plato

ἢ Δία -- ἐπιλανθανόμενον . μόνος ἐγρηγορώς refers to Il. II 1—4: the incident itself is narrated in Il. XIV 294 ff. For the postponement of the relative ἅ cf. IV 425 C. The effect is to throw emphasis on μόνος ἐγρηγορώς—that Zeus should forget what he had purposely kept awake to devise makes the scandal all the worse —and brings it into sharper contrast with καθενδόντων—ἀνθρώπων. ὡς must be taken with ἐπιλανθανόμενον, the construction being ἢ ποιεῖν Δία ὡς ἐπιλανθανόμενον: cf. II 383 A. Stallbaum explains ὡς μόνος ἐγρηγορώς as “ut solus vigil”: while J. and C. supply ἀκούειν after ἤ. Neither view seems to me at all satisfactory. The text has been often called in question. Instead of ὡς Hermann reads καί: Herwerden and Richards suggest ὅσα (dropping ἅ before ἐβουλεύσατο). The best emendation is perhaps Jackson's εἷς for ὡς (Journal of Phil. IV p. 147), but I see no good reason why ὡς cannot be construed with ἐπιλανθανόμενον. The pause which on this view is necessary after ὡς helps still further to increase the stress on μόνος ἐγρηγορώς, which Plato certainly intended to emphasize.