Quam Singulari lays out a thorough case for early admittance of the sacraments. This takes up a good chunk of the document. But the apologetic core is important to look at as a whole:
No less worthy of condemnation is that practice which prevails in many places prohibiting from Sacramental Confession children who have not yet made their First Holy Communion, or of not giving them absolution. Thus it happens that they, perhaps having fallen into serious sin, remain in that very dangerous state for a long time.
But worse still is the practice in certain places which prohibits children who have not yet made their First Communion from being fortified by the Holy Viaticum, even when they are in imminent danger of death; and thus, when they die they are buried with the rites due to infants and are deprived of the prayers of the Church.
Such is the injury caused by those who insist on extraordinary preparations for First Communion, beyond what is reasonable; and they doubtless do not realize that such precautions proceed from the errors of the Jansenists who contended that the Most Holy Eucharist is a reward rather than a remedy for human frailty. The Council of Trent, indeed, teaches otherwise when it calls the Eucharist, “An antidote whereby we may be freed from daily faults and be preserved from mortal sins.” This doctrine was not long ago strongly emphasized by a Decree of the Sacred Congregation of the Council given on December 20, 1905. It declared that daily approach to Communion is open to all, old and young, and two conditions only are required: the state of grace and a right intention.
Moreover, the fact that in ancient times the remaining particles of the Sacred Species were even given to nursing infants seems to indicate that no extraordinary preparation should now be demanded of children who are in the happy state of innocence and purity of soul, and who, amidst so many dangers and seductions of the present time have a special need of this heavenly food.
The abuses which we are condemning are due to the fact that they who distinguished one age of discretion for Penance and another for the Eucharist did so in error. The Lateran Council required one and the same age for reception of either Sacrament when it imposed the one obligation of Confession and Communion.
Therefore, the age of discretion for Confession is the time when one can distinguish between right and wrong, that is, when one arrives at a certain use of reason, and so similarly, for Holy Communion is required the age when one can distinguish between the Bread of the Holy Eucharist and ordinary bread-again the age at which a child attains the use of reason.
This section might as well be titled “Remedy, Not Reward.” The sacramental life is not earned by good conduct. The sacramental life is not earned by academic achievement, or even completion. The sacramental life is not earned by patronage, connections, or political accessibility. It is offered to all who satisfy two basic spiritual requirements.
I would hesitate to label as “jansenist” all the Catholic urgings to “defend” the sacraments. I happen to think that God is a good bit tougher than we give credit. But the sacramental life is a very precious gift and grace. It is natural to want everyone else to have that same experience of grace that we have known. Still, I think the case for early reception of the sacraments is strongly logical. Of course, I’ve had a lifelong experience with it. I’ve seen the benefits and fruitfulness of it. That so many believers do receive Communion as children only later to go inactive is less a condemnation of them or the practice than an indictment of the poverty of the Church’s ministry to the young. And to parents.