Philo Judaeus De Posteritate Caini 172

But when Moses says here that Seth sprung up as another or different seed, he does not say from which it was different; was it different from Abel who was treacherously slain, or from Cain who slew him? But may we not say perhaps that the original seed from which each of these sprung was different? That from which Cain sprung, inasmuch as it was hostile; for a thirst for virtue is the most hostile thing possible to that deserter, wickedness; that from which Abel sprung, as friendly and kindred; for that which is beginning to exist is a different thing from, but not a contrary thing to, that which is perfected; and so that which pertains to creation is different from that which pertains to the uncreate.