All of creation is good, though "good" of lesser or greater orders. Poison, Augustine points out, may have evil uses, but it is still a good when it is used as a curative. When we see things in their proper place and according to their Divinely ordained natures, we see that evil has no independent existence of its own, and only exists when the "hierarchy of created realities" is disrupted in its order. When we take a lesser good and turn it into a greater, we create (if one may use that verb--and Augustine would say we shouldn't) evil. So again, as with poison, it only becomes evil when we stop using it for its proper purpose and put it where it does not belong in the hierarchy of being.
We can understand--even as we condemn--those such as the Manicheans who posit an evil creator. They are mistaking a categorical error for a physical error, and it is our job as Christians to highlight that the nature of sin is merely physical, but is a rebellion (both physical and spiritual) against the proper order of the universe. We have tried to lift ourselves above our place and take God's proper place in existence.
Even some Christians occasionally fall into the line of thought described in the previous chapter--namely, Origin and his followers. This is unfortunate and requires correction--especially by the idea that the existence of sin in God's creation does not lead to the conclusion that all things are as sinful as they could possibly be. Ruining a painting by darkening the tint does not obliterate all beauty that was there to begin with, and it certainly does not negate the artist's purpose in creating it.
What's more, we have to be careful to avoid the conclusion that Origin seems to reach that sin is most fully expressed in physical bodies. If this were the case, the devil would have been punished by being turned into one. We reminded ourselves to avoid these near-Gnostic extremes when we remember God's purpose and order and sovereignty in Creation--He made the physical world for the same reason that He made the spiritual world: because He is good and it is in His nature to express that goodness through the act of creation.