Just because something is an old teaching does not make it true nor a new teaching make it false. Nevertheless, Catholics follow Tradition, which means what has been handed on. Never in the 2000 years of Church history has the Catholic Church taught that unbaptized infants can attain the beatific vision. On the contrary, for 2000 years it has taught that they cannot attain the beatific vision on account of their state of original sin, which without baptism, the Church has always taught, they cannot become children of God. Scripture teaches that we are all “by nature children of wrath” (Eph 2:3). The ones who taught that unbaptized infants could be saved and attain heaven were the Pelagians, who were excommunicated as heretics in a General Council and in the Council of Carthage (the same Council that first canonized Scripture–howbeit a local Council) this very proposition was anathematized.
Yes, this is exactly it. Babies going to Heaven. It’s simple. Who in the world would teach against it unless they had to? It’s a no brainer – babies going to Heaven. If they were, the Church would teach it clearly, explicitly, and there wouldn’t be the slightest controversy about it, wouldn’t you think?
But it is just the opposite. 2,000 years.
Speaking of weight, the great thing about linking directly to the Vatican is that you know from whence comes the authority and authorship. So much on the internet is anonymous and undocumented.
That’s exactly why I like to quote catechisms, saints, and so forth.

And the good priest in the sermon who gives an example of what has weight and what is weightless, and simply verbiage from a commission.
“Unless a man be born again of water and the Holy Ghost, he cannot enter into the kingdom of God.” Consequently it became necessary to baptize children, that, as in birth they incurred damnation through Adam so in a second birth they might obtain salvation through Christ. Moreover it was fitting that children should receive Baptism, in order that being reared from childhood in things pertaining to the Christian mode of life, they may the more easily persevere therein; according to Proverbs 22:5: “A young man according to his way, even when he is old, he will not depart from it.” This reason is also given by Dionysius (Eccl. Hier. iii).
St. Thomas Aquinas
Infants that are born and die, and who do not receive Baptism, will they be saved?
No, they cannot be saved; for there is only one means of being incorporated with Jesus Christ and of receiving His grace, without which there is no salvation among men (LXVIII.3).
- The Catechism of the Summa Theologica of Saint Thomas Aquinas, Fr. R.P. Pegues