Did Church ever have a formal teaching on unbaptized babies who died? Did Council of Carthage(418) show a formal view?
There is no formal teaching. There have been various ideas over the centuries as Carholic thinkers tried different ways of balancing the teaching on Original Sin with what we know of God’s mercy.
It
is a formal teaching that one cannot go to Heaven without sanctifying grace, that humans are ordinarily born without sanctifying grace as a result of Original Sin, and that Baptism is the only means that has been revealed to us for imparting sanctifying grace initially.
The question thus arose of the fate of those who have no personal sin but die without Baptism, infants who die very young being the most obvious case.
Some, like St. Augustine, applied the “rules” strictly and believed that even an unbaptized infant would go to Hell like any other sinner.
Later thinkers could not see a way around that basic principle, but felt that a merciful God would make some distinction between a soul that had died unrepentant of personal sins and a soul that had merely died in the condition of Original Sin before its own moral capacities even developed.
At least one council (Florence or Lyons, I think) emphasized that there are different levels of punishment in Hell, such that those who died in Original Sin only would suffer less (presumably far less) than those who had died in mortal sin.
In time the notion of “suffering less” became “not suffering at all” and even “having as much happiness as one can have outside of Heaven.” This afterlife was envisioned as taking place on the outer borders of Hell, and thus the region became known as Limbo (from the word for a border or fringe). That led to the strange circumstance of a part of Hell whose inhabitants were happier than anyone on Earth.
Meanwhile, the Church has always speculated that some unbaptized adults can actually make it to Heaven, not merely Limbo. Those who suffer martyrdom for Christ before formal Baptism are said to have undergone the “baptism of blood.” Catechumens who die for other reasons before their baptism are presumed to receive the fruits of the sacrament by virtue of their sincere desire for it. More recently we have extended the idea of “baptism of desire” to those who are “invincibly ignorant” of the necessity of the Christian faith – those who would be baptized if they but knew it was required, but who lack that knowledge. As Catholics who prefer a stricter interpretation of the necessity of baptism are quick to remind us, none of these are formal teachings either. God has not revealed to us what becomes of any of the unbaptized, no matter how close they came to the sacrament. Like Limbo, they are theological speculations based on the reasonable notion that God wants all souls in Heaven and is not going to condemn a soul on a technicality.
The latest thinking on the fate of unbaptized infants is completely in line with this trend toward a greater appreciation of God’s mercy. It’s not a sudden about-face. As illustrated by the notions of baptism of blood and desire, we have long understood that God does not require a human to perform the sacrament of Baptism before He can save someone. Thus, rather than stopping at the point of condemning unbaptized infants to even the nice part of Hell, the magisterium has decided that it makes the most sense to draw no firm conclusion but trust in God’s mercy to supply what His followers sometimes cannot.
Usagi