2: Some say that children would have been born, not with
the righteousness of grace, which is the principle of merit, but with
original righteousness. But since the root of original righteousness,
which conferred righteousness on the first man when he was made,
consists in the supernatural subjection of the reason to God, which
subjection results from sanctifying grace, as above explained (Q. 95,
A. 1), we must conclude that if children were born in original
righteousness, they would also have been born in grace; thus we have
said above that the first man was created in grace (Q. 95, A. 1).
This grace, however, would not have been natural, for it would not
have been transfused by virtue of the semen; but would have been
conferred on man immediately on his receiving a rational soul. In the
same way the rational soul, which is not transmitted by the parent,
is infused by God as soon as the human body is apt to receive it.

From this the reply to the third objection is clear.
_______________________

SECOND ARTICLE [I, Q. 100, Art. 2]

Whether in the State of Innocence Children Would Have Been Born
Confirmed in Righteousness?

Objection 1: It would seem that in the state of innocence children
would have been born confirmed in righteousness. For Gregory says
(Moral. iv) on the words of Job 3:13: "For now I should have been
asleep, etc.": "If no sinful corruption had infected our first parent,
he would not have begotten 'children of hell'; no children would have
been born of him but such as were destined to be saved by the
Redeemer." Therefore all would have been born confirmed in
righteousness.

Obj. 2: Further, Anselm says (Cur Deus Homo i, 18): "If our first
parents had lived so as not to yield to temptation, they would have
been confirmed in grace, so that with their offspring they would have
been unable to sin any more." Therefore the children would have been
born confirmed in righteousness.

Obj. 3: Further, good is stronger than evil. But by the sin of the
first man there resulted, in those born of him, the necessity of sin.
Therefore, if the first man had persevered in righteousness, his
descendants would have derived from him the necessity of preserving
righteousness.

Obj. 4: Further, the angels who remained faithful to God, while the
others sinned, were at once confirmed in grace, so as to be unable
henceforth to sin. In like manner, therefore, man would have been
confirmed in grace if he had persevered