James Adam, The Republic of Plato

καὶ δἰ ὃ κτλ. explains and amplifies ὃ—ἀγαθόν. Wealth is the cause of oligarchy, that ‘on account of’ which it was established: cf. 550 D ff., 551 C, 555 B (τοῦ προκειμένου ἀγαθοῦ). The reading δἰ οὗ (see cr. n.) would make wealth the means or instrument in producing the result, and this it was not, except in the loose sense in which the προκείμενον ἀγαθόν is also a means. I formerly conjectured δἰ ὃ αὖ (Cl. Rev. IV p. 357), but αὖ is unsuitable. For the corruption in the MSS see note on διὰ τοῦτο X 610 D. Jowett wrongly translates καθίστατο by ‘was maintained.’

πλοῦτος. See cr. n. The majority of editors reject ὑπέρπλουτος: rightly, for the word is not used except as an adjective. A host of emendations has been suggested, ὁ πέρα πλοῦτος (Richter Fleck. Jb. 1867 p. 146), ὑπέρπλουτος <πλοῦτος> (Stallbaum), ὑπὲρ πλούτου (Madvig—but the use of ὑπέρ is not above suspicion), που πλοῦτος (Campbell), ὑπερπλουτεῖν (apud J. and C.), εἴπερ τι, πλοῦτος (Apelt Berl. Phil. Woch. 1895 p. 968). Stephanus' conjecture γίγνεσθαι ὑπέρπλουτον was adopted by Ast. The expression ὑπέρπλουτος πλοῦτος occurs in Joan. Damasc. III 733 A ed. Migne, but in a highly rhetorical passage and without any reference to Plato. It is probably best to read πλοῦτος, with Schneider and Hermann. ὑπέρπλουτος may have originally been a marginal note intended to recall ὑπέρπλουτοι in 552 B.

ἀπώλλυ. 555 C—557 A.

ἐλευθερίαν. See 557 B note