I answer that, As stated above (A. 1), sin incurs a debt of punishment through disturbing an order. But the effect remains so long as the cause remains. Wherefore so long as the disturbance of the order remains the debt of punishment must needs remain also. Now disturbance of an order is sometimes reparable, sometimes irreparable: because a defect which destroys the principle is irreparable, whereas if the principle be saved, defects can be repaired by virtue of that principle. For instance, if the principle of sight be destroyed, sight cannot be restored except by Divine power; whereas, if the principle of sight be preserved, while there arise certain impediments to the use of sight, these can be remedied by nature or by art. Now in every order there is a principle whereby one takes part in that order. Consequently if a sin destroys the principle of the order whereby man's will is subject to God, the disorder will be such as to be considered in itself, irreparable, although it is possible to repair it by the power of God. Now the principle of this order is the last end, to which man adheres by charity. Therefore whatever sins turn man away from God, so as to destroy charity, considered in themselves, incur a debt of eternal punishment.
Reply Obj. 1: Punishment is proportionate to sin in point of severity, both in Divine and in human judgments. In no judgment, however, as Augustine says (De Civ. Dei xxi, 11) is it requisite for punishment to equal fault in point of duration. For the fact that adultery or murder is committed in a moment does not call for a momentary punishment: in fact they are punished sometimes by imprisonment or banishment for life—sometimes even by death; wherein account is not taken of the time occupied in killing, but rather of the expediency of removing the murderer from the fellowship of the living, so that this punishment, in its own way, represents the eternity of punishment inflicted by God. Now according to Gregory (Dial. iv, 44) it is just that he who has sinned against God in his own eternity should be punished in God's eternity. A man is said to have sinned in his own eternity, not only as regards continual sinning throughout his whole life, but also because, from the very fact that he fixes his end in sin, he has the will to sin, everlastingly. Wherefore Gregory says (Dial. iv, 44) that the "wicked would wish to live without end, that they might abide in their sins for ever."
Reply Obj. 2: Even the punishment that is inflicted according to human laws, is not always intended as a medicine for the one who is punished, but sometimes only for others: thus when a thief is hanged, this is not for his own amendment, but for the sake of others, that at least they may be deterred from crime through fear of the punishment, according to Prov. 19:25: "The wicked man being scourged, the fool shall be wiser." Accordingly the eternal punishments inflicted by God on the reprobate, are medicinal punishments for those who refrain from sin through the thought of those punishments, according to Ps. 59:6: "Thou hast given a warning to them that fear Thee, that they may flee from before the bow, that Thy beloved may be delivered."
Reply Obj. 3: God does not delight in punishments for their own sake; but He does delight in the order of His justice, which requires them.
Reply Obj. 4: Although punishment is related indirectly to nature, nevertheless it is essentially related to the disturbance of the order, and to God's justice. Wherefore, so long as the disturbance lasts, the punishment endures. ________________________
FOURTH ARTICLE [I-II, Q. 87, Art. 4]
Whether Sin Incurs a Debt of Punishment Infinite in Quantity?
Objection 1: It would seem that sin incurs a debt of punishment infinite in quantity. For it is written (Jer. 10:24): "Correct me, O Lord, but yet with judgment: and not in Thy fury, lest Thou bring me to nothing." Now God's anger or fury signifies metaphorically the vengeance of Divine justice: and to be brought to nothing is an infinite punishment, even as to make a thing out of nothing denotes infinite power. Therefore according to God's vengeance, sin is awarded a punishment infinite in quantity.
Obj. 2: Further, quantity of punishment corresponds to quantity of fault, according to Deut. 25:2: "According to the measure of the sin shall the measure also of the stripes be." Now a sin which is committed against God, is infinite: because the gravity of a sin increases according to the greatness of the person sinned against (thus it is a more grievous sin to strike the sovereign than a private individual), and God's greatness is infinite. Therefore an infinite punishment is due for a sin committed against God.
Obj. 3: Further, a thing may be infinite in two ways, in duration, and in quantity. Now the punishment is infinite in duration. Therefore it is infinite in quantity also.