Some notes and a brief summary:
Those who deny original sin have to explain why death is prevalent even among infants and imbeciles. Romans says the wages of sin is death. If the curse of death is universal, it necessarily follows that the wages of sin is universal. Yet, how can they be held accountable for sin before the giving of the law (Romans 5:12-13)? Only something like the Covenant of Works can really answer this question. Yes, the curse of death is imputed to us (as our Eastern friends tell us). Yes, death is the enemy. But as Paul makes clear, how can their be death without the wages of sin?
Incidentally, we deny that sin is a substance. It is a moral quality in the soul, but it is not the soul.