It is difficult to define original sin because there is nothing like it in the world. But it is better to describe it than defining it.
1. Adam and Eve and their initial state of innocence.
When God created Adam and Eve He knew they would fall into sin. But in spite of that He created them in a state of original innocence, pleasing to Him, but with a free will, capable of disobedience. He had to create them in original innocence prelude to the fall so we can notice the fall. After that initial state of innocence, they were tested to see whether they were deserving of permanent residency in Paradise or to be expelled. Unfortunately the latter was the case.
2. God gives each one of us the same initial state of innocence.
God, in His wisdom and goodness has given each man the same privilege after the fall: that every being that is born is conceived with original innocence, pleasing to God but with a free will capable of disobedience. This state lasts for a very short period in a child’s life. And this brief time is that which Christ refers to when He said to be like little children. In their innocence these children have infused knowledge, “for it is to such that the kingdom of God is revealed.”
That brief moment is described by the Fathers in a manner that one would think they were describing saints. And indeed, during that brief moment, children are saints…. But not confirmed in grace, as saints are.
3. What is original sin.
Original sin is a state in which souls will eventually lose their original innocence. Mary, in her Immaculate Conception, was conceived without original sin and so she did not inherit the prospect of losing that original innocence. But everyone else can easily lose it. And when that original innocence will be lost depends greatly on how a child is brought up by the Church and / or by its parents.
4. The function of Baptism vs. Original sin
The curse of Original Sin is that tendency to choose evil so that eventually the child will lose his original innocence and begin to be influenced by his concupiscence. When he succumbs to the concupiscence, then he sins.
Baptism is supposed to give the child grace in order to help him keep that original innocence longer, thus giving the parents ample time to help preserve that original innocence. The tendency to sin will definitely be there. But the Church and the parents can help to lessen or nullify its deadly effects through proper Christian upbringing or education.
5. The role of Church and parents.
How can parents maintain that original innocence in their children? Through a disciplined life. St. Thomas of Aquinas mentioned “to do good,” in accordance to the commands of Christ as described in the Apostolic Commission. Or to be perfectly good. Of course, this will take some time. As the original innocence of a child disappears, the child cannot be good immediately. So the Christian training of the child must begin as soon as possible with this goal….of preserving his original innocence that could disappear sooner than later. Evidently some parents were able to do this as in the case of the parents of St. Therese of Lisieux. St. Thomas of Aquinas preserved his original innocence because of his stay in a Benedictine monastery (Monasteries were supposed to preserve that original innocence that is why infants used to be received as in the case of Sts. Maurus and Placid.)
6. Remaining a child vs becoming a child again.
So a child, though unbaptized, is born holy. (Perhaps this is the reason why the Pope has finally declared that unbaptized babies who die go straight to Heaven.) Original sin is the fact that he will, eventually, lose this holiness. Christian upbringing and monasticism were meant to help preserve original innocence for as long as possible, so that the child would never be a slave of concupiscence. This is what probably happened to St. Thomas of Aquinas and St. Therese of Lisieux, that is why they seem to have never sinned. But for most of us, we share in the lot of the sea of humanity. Though we have a recourse when we lose this original innocence: REPENTANCE. We can be a child once more, yes, we can be born again!
7. Modern environment hastens the removal of innocence.
For babies, especially baptized ones, we can do so much for the sanctification of their souls. It is the neglect of the work of sanctifying souls that has brought the whole church, with its leaders and people, to its present sad state. It is so easy to make saints out of children. They were born saints. All we have to do is to preserve or maintain that holiness in them. With secularism, modernism, relativism, hedonism all around us, we have hastened the loss of our children’s original innocence or holiness….what a waste!!