 Besides the gift of having a mind like a concordance, he also shows familiarity with philosophical terms and categories of the Stoics, Epicureans, and Pythagoreans (from whom, with Philo, he derives his occasional number symbolism hermeneutic).His works also seem to cite passages from the deuterocanonical books of the Old Testament as well as Barnabas, the Shepherd of Hermas and the Acts of John.According to Bart Ehrman, his canon extended to at least include Barnabas and the Shepherd.