Question Fifth. On the Origin of Sin.

321. Genesis of sin. 1. Sin, which is a deliberate act of the will, is completed by these, as it were, grades.

a. First there is the proposal of an evil thing, in that by the work of some power, sense, phantasy, or intellect, some object is offered to the will which it cannot embrace without violation of law.

b. Then there arises in the appetite, sensitive and rational, or in the rational alone according to the nature of the object, an inclination toward the proposed object with a certain pleasure: for by natural necessity the appetite is borne toward its object and is delighted in possession of it.

Since motions of concupiscence arise by their nature in man when an object, good or evil, has been proposed, it follows that any man experiences motions of this kind, and that they are more or less frequent and vehement according to the diversity of temperament and circumstances.

c. Afterward the intellect adverts both to the object toward which the will is inclined and to its moral malice, i.e. to the law prohibiting the volition of it, and therefore to the obligation of repelling the temptation.

If the will adheres to the object toward which it is inclined before the intellect adverts to its malice, that adherence cannot be sin.

d. Finally the will freely determines itself to the act, and indeed either turns itself away from the object offered, resisting the temptation, or does not turn itself away from it. But if it does not turn itself away, voluntary adherence to the evil thing now begins on account of the temptation not rejected, which adherence is consummated through positive consent.

Sacred Scripture graphically describes the origin of sin with these words: Each one is tempted, drawn away and enticed by his own concupiscence. Then concupiscence, when it has conceived, brings forth sin; but sin, when it has been consummated, generates death.¹ That is, concupiscence, offering the object of sin, entices the will to consent; but if the will, not repelling the temptation, begins to adhere to the evil thing, from this, as it were, marriage between concupiscence and the will, positive consent, sin, is generated as fruit, whose effect is the spiritual death of the soul.

2. The efficient cause of sin is the human will alone, freely determining itself to an act prohibited by law; nevertheless it can be allured and incited to sin in diverse ways. That which allures the will to sin is either temptation to sin or is at the same time an occasion of sin; but each contains a danger of sinning.

¹ Jas. 1, 14 ff.