καὶ τὴν πρώτην
ὑπόστασιν ἔσχεν ἰδίαν.
ὑπόστασις is rare in Josephus (otherwise only at
Ant. 18.24, which is textually uncertain); it has philosophical connotations of “essence” or “true substance.” The stress falls on “its own” (
ἰδία), suggesting something distinct. The point is emphasized here in anticipation of the “slanders” that Judeans were in fact (renegade and polluted) Egyptians; cf. 1.104, 228-29, 252-53, 278, 298; 2.289 (in summary). Later, Josephus will declare that “the ancestors of our people were Chaldean” (1.71), but he cannot allow any original “mixing” with Egyptians; on the cultural politics see Barclay 2004.
Ant. 1.148 had begun the history of the “Hebrews” with Abraham, of Chaldean descent (cf. 1.158-69). The Egyptian issue is alluded to in
Ant. 2.177, but ethnic purity was not there given the prominence this comment suggests.