Monotheism was a fundamental article of faith from the beginning of the church. God was defined as omnipotent, as the ruler of the universe, leading the human race on the way to salvation. Creation out of nothing was originally a Hellenistic-Jewish formula expressing the power of the creator God. The most influential philosophical school in the first two centuries after Christ was Stoicism. Philo was probably from one of the noble families of Jewish Alexandria and had received an extensive philosophical training. A little later than Justin, in the seventies of the second century, Athenagoras of Athens wrote his apology: Legatio pro Christianis. His book is more sophisticated than Justin's apologies. During the second half of the second century the 'Great Church' began to resist the propaganda of Marcionites and Gnostics more and more rigorously. The most important Christian theologians of the time before and around 200 were Theophilus, bishop of Antioch, and Irenaeus, bishop of Lyons.