A number of late Stoic sources describe either ethical concepts or a supposed universal belief in gods as being innate in the human animal. Though Chrysippus himself is known to have spoken of "implanted preconceptions" (ε¨μϕυτοιπρολν´ψειζ) of good and bad, scholars have typically argued that the notion of innate concepts of any kind would have been entirely incompatible with his theory of knowledge. Both Epictetus' notion of innate concepts of good and bad and the references to an innate belief in gods by other philosophers of the Roman era are thus generally held to be later developments, probably owing to a Platonist-Stoic syncretism. Review of the evidence, however, shows that Chrysippus, like Epictetus, held ethical concepts to represent a special category of conception in that their formation was guaranteed by oikeiôsis. Unlike other concepts, that is, these represent a formal conceptualization of an innate tendency to distinguish between things fitting for one's constitution and things not fitting that all animals, according to the Stoics, bring to their empirical experiences. While the notion that human belief in gods is similarly innate does seem to have been a later development, it too was explained with reference to oikeiôsis rather than resulting from a simple "syncretism."