I’ve done things I know are wrong. I’ve been too angry, not angry enough, selfish, resentful, lustful, and lazy. We humans are reflective, we can see the rules by which we ought to live, but we are unable to live by them. Original sin is the paradox of creatures with a moral mind but without moral muscle. With God in the picture, the puzzle is even more pointed: why would an all-good God make such morally compromised creatures?
Genesis says that humans were created from the dust of the earth, which God breathed into (Genesis 2:7). This colorful poetic language reveals that humans are the intersection of the material and spiritual worlds.
Catholics accept that hominids evolved from simpler life forms, and ultimately from the very material of the earth. These hominids may have looked human, but they did not have souls, they did not have a capacity for God. God’s breath carried two spiritual gifts. First, God placed into Adam and Eve a rational soul. The rational soul is what gives us our capacity for reflection and moral knowledge.
Second, there was a more temporary and conditional gift called original justice. Before the fall, Adam and Eve would have not only known how to live rightly, but would have been able to do so easily. They would have eaten at the right times, in the right amounts, related harmoniously to each other, used the goodness of the garden for their wellbeing and sometimes their enjoyment, and done all this without a second thought. Original justice gave us the capacity to live according to moral principles which we knew thanks to our rational souls. In sum, the rational soul is the moral mind while original justice was the moral muscle.
The “dust” that comprises our material bodies is a heritage from our hominid ancestors, molded by billions of years of evolutionary forces into adaptively successful creatures. The traits that have made us successful hominids: effective senses, instincts for tool use, acquiring food and resources, sex drive, are a mixed bag morally speaking. God seems to delight in using secondary causes as part of his plan. He consents to all kinds of imperfections, sin, evil, that he does not directly will.
God’s plan for humanity was for original justice and rationality to exist together alongside our animal nature. Our rational soul was placed into a wild forest of animal instinct, an explorer in the jungle, able to see the animals but not to control them. Original justice gave the explorer the power to “control the animals” of the human passions. However, in His wisdom, God gave us rationality and original justice under different conditions. Our rational soul is permanent, and once created will always exist. Original justice was given conditionally, and it could be withdrawn if God’s will was contravened, which is of course what happened.
According to the catechism (CCC 405), original sin consists in the withdrawal of the gifts of original justice, following the fall. Original sin, then, is the state of having some knowledge of how we ought to put our inherited bodily drives and capacities to use, but lacking the virtues and spiritual ordering to do so easily, consistently or joyfully. The catechism states that original sin is i) attached to human nature (CCC 404) ii) transmitted rather than merely imitated (CCC 419) and iii) also the lack of original justice (CCC 405). Original sin is composed of two parts, one negative and one positive. Its positive part is the moral jumble of our evolutionary heritage, which is clearly i) attached to human nature and ii) transmitted rather than merely imitated. Its negative component is iii) the lack of original justice.
So original sin is not some spiritual taint that is somehow passed from parent to child, it is the genetic mixed bag of our material heritage after the fall without the guidance of original justice. This view preserves the goodness of God, his providence, and the nobility of human creatures. It was the first of two great condescensions of God to grant the “divine spark” of rationality to material, dusty creatures. He first stooped to imprint his image on mere dust, and later became it.
God delights in using secondary causes. Just as he used the Apostles, flawed and sinful men, yet made remarkable and holy by the touch of Christ, to spread the Gospel. So too, he used natural selection, a morally ambiguous process, to prepare our bodies to receive rationality. Just as Christ allowed Peter to betray Him, and transfigured this betrayal through forgiveness, so too he imprinted a spark of His divine life into greedy, lustful animals, and transfigured them through his gift of original justice. Original sin is, then, the collision of a finite, material world with the divine spark, and it causes a wound which God is healing in His own way and in His own time.