Although God has created all of us good (He is the "author of all natures, but not of their defects"), we have all sinned in Adam and so deserve the punishment for our sin. "Thus, from a bad use of free choice, a sequence of misfortunes conducts the whole human race, excepting those redeemed by God, from the original canker in its root to the devastation of a second and endless death."
In some ways, this can be intolerable to modern Americans--how dare we be judged for the actions of another? (We forget, of course, that this is exactly what happens in the Gospel, where Christ is judged for our actions...) But this fails to understand the true nature of a human being--we are not isolated individuals cut off from each other. We are better compared to a plant with Adam as our root. If the root is rotten, the whole plant is doomed no matter how bright the leaves. We need to be transplanted into a new root, which is what God does by grace to those whom He will save.
On his sin, Adam immediately experienced one kind of death--separation of the soul from God. Years later, he experienced a second, that of separation of the soul from the body. "Ultimately, it will be followed by a second one, unless, by God's grace, man is delivered from it."
Some philosophers ridicule the Christian idea that we can be both eternally happy and immortally bodied. Yet they fail to remember that the greatest of the pagan philosophers, Plato, believed exactly the same thing.