My new article on this subject is here: All little children go to Heaven — On the salvation of infants who die without baptism, and the idea of a limbo of children in Hell.
excerpts from the article:
Here is my theological position: The fringe of Hell exists as a place of eternal but lesser punishment for adults who die in a state of original sin alone. These adults died in that state because they committed the actual mortal sin of omission of never having found sanctifying grace in their lives, despite ample opportunity. So no one at all ever goes to Hell, except due to unrepentant actual mortal sin.
This fringe of Hell has been called ‘the limbo of the children’ (“limbus infantium” or “limbus puerorum”), but the term is a severe misnomer. No prenatals, no infants, no young children are ever sent by God to that place, nor to Hell at all, even if they die without a formal Baptism. For they receive a baptism of blood, just like the Holy Innocents did. So they die in a state of grace, and they will be very happy and perfectly fulfilled forever in Heaven.
The Magisterium teaches that we cannot be happy and fulfilled without supernatural happiness. Therefore, no one can be happy in the limbo of Hell.
“Human beings cannot completely fulfill themselves, they cannot be truly happy without God.” (Pope Benedict XVI)
“Without God, man cannot fully find himself, nor can he find his true happiness.” (Pope John Paul II)
Pope Benedict XVI and Pope John Paul II taught that human beings cannot be truly happy without God. The Catechism teaches that Hell is eternal separation from God (CCC, n. 1035). Therefore, no one can be happy in Hell.
“It is a divine law that those only attain everlasting happiness who have by such faithful following reproduced in themselves the form of the patience and sanctity of Jesus Christ: ‘for whom He foreknew, He also predestined to be made conformable to the image of His Son; that He might be the first-born amongst many brethren’ (Romans viii., 29).” (Pope Pius X).
Pope Pius X taught that it is a Divine law of God that no one can attain everlasting happiness, except by being conformed to the image of Christ, having in themselves the sanctity of Christ. But this sanctity is only found in sanctifying grace by baptism. Therefore, souls who die without any form of baptism, even if in a state of original sin only, cannot have everlasting happiness in Hell, nor in any form of Limbo.