Q: Whether Venial Sin Can Be in Anyone with Original Sin Alone?

A: On the contrary,
Man is punished for original sin in the children's limbo, where there is no pain of sense as we shall state further on (II-II, Q. 69, A. 6): whereas men are punished in hell for no other than mortal sin. Therefore there will be no place where a man can be punished for venial sin with no other than original sin.

I answer that,
It is impossible for venial sin to be in anyone with original sin alone, and without mortal sin. The reason for this is because before a man comes to the age of discretion, the lack of years hinders the use of reason and excuses him from mortal sin, wherefore, much more does it excuse him from venial sin, if he does anything which is such generically. But when he begins to have the use of reason, he is not entirely excused from the guilt of venial or mortal sin. Now the first thing that occurs to a man to think about then, is to deliberate about himself. And if he then direct himself to the due end, he will, by means of grace, receive the remission of original sin: whereas if he does not then direct himself to the due end, as far as he is capable of discretion at that particular age, he will sin mortally, through not doing that which is in his power to do. Accordingly thenceforward there cannot be venial sin in him without mortal, until afterwards all sin shall have been remitted to him through grace.

Reply Obj. 1: Venial sin always precedes mortal sin not as a necessary, but as a contingent disposition, just as work sometimes disposes to fever, but not as heat disposes to the form of fire.

Reply Obj. 2: Venial sin is prevented from being with original sin alone, not on account of its want of connection or likeness, but on account of the lack of use of reason, as stated above.

Reply Obj. 3: The child that is beginning to have the use of reason can refrain from other mortal sins for a time, but it is not free from the aforesaid sin of omission, unless it turns to God as soon as possible. For the first thing that occurs to a man who has discretion, is to think of himself, and to direct other things to himself as to their end, since the end is the first thing in the intention. Therefore this is the time when man is bound by God's affirmative precept, which the Lord expressed by saying (Zech. 1:3): "Turn ye to Me . . . and I will turn to you."

TREATISE ON LAW (QQ. 90-108)

QUESTION 90

OF THE ESSENCE OF LAW (In Four Articles)

We have now to consider the extrinsic principles of acts. Now the extrinsic principle inclining to evil is the devil, of whose temptations we have spoken in the First Part (Q. 114). But the extrinsic principle moving to good is God, Who both instructs us by means of His Law, and assists us by His Grace: wherefore in the first place we must speak of law; in the second place, of grace.

Concerning law, we must consider: (1) Law itself in general; (2) its parts. Concerning law in general three points offer themselves for our consideration: (1) Its essence; (2) The different kinds of law; (3) The effects of law.

Under the first head there are four points of inquiry:

(1) Whether law is something pertaining to reason?

(2) Concerning the end of law;

(3) Its cause;

(4) The promulgation of law.