ἀγαθοὶ δὲ ἐγένοντο διὰ τὸ φῦναι ἐξ ἀγαθῶν → they were virtuous because they were sprung from virtuous men, virtuous they were because they were sprung from men of virtue
3ᵉ pl. pf. Pass. ion. de θάπτω.