Alan Jacobs, in his new book Original Sin, lists “five distinct beliefs” which make up an Augustinian anthropology (or a belief in original sin):
You must believe that everyone behaves in ways that we usually describe as selfish, cruel, arrogant, and so on. You must believe that we are hard-wired to behave in those ways and do not do so simply because of the bad examples of others. You must believe that such behavior is properly called wrong or sinful, whether it’s evolutionarily adaptive or not. You must believe that it was not originally in our nature to behave in such a way, but that we have fallen from a primal innocence. And you must believe that only supernatural intervention, in the form of what Christians call grace, is sufficient to drag us up out of this pit we’ve dug for ourselves.