Summa Theologiae Moralis, vol. I: De Principiis

S. Th. I-II, q. 71, a. 6; q. 72, a. 1 and 5; q. 73, a. 2; C. Gent. III, 9; de Malo, q. 1, a. 1; q. 2.

425. Sin consists of two constitutive elements, as it were metaphysical parts, which are related as matter (indeterminate) and form (determining) in natural beings, and which are accordingly called material and formal. In sin itself there is found:

1° a positive and material element: the substance of the act considered, not in physical being insofar as it tends to any good whatsoever (for thus it is not a human or moral act, nor therefore morally evil, and accordingly is not a constitutive element of sin but is presupposed to it), but in moral being insofar as it unduly tends to some created good which cannot be referred to the last end: it is an undue conversion to a creature; — and

2° a privative element which necessarily follows from the first, namely the very privation of rectitude or due ordination to the last end: it is an aversion or turning away from God. This is the formal element* because it determines the material to this, that it be sin: for conversion to a creature would not be theological sin unless through it man also stood inordinately with regard to the last end. — In other words: the material of sin is the voluntary act itself by which man tends to something contrary to the eternal law; the formal is the very deformity of the act or withdrawal from the eternal law.

426. Observation. — The material of sin is not to be confused with material sin: in the latter indeed there is no formal malice, indeed it can be a formally good act; the material of sin is its constitutive element which inseparably has malice attached to it. Thus Jacob's approach to Leah is the material of sin with respect to Jacob, but the material of sin with respect to Leah; taking money from one who is violently brought to it is material sin, the material of sin for the one who inflicts the violence.

Likewise the formal of sin and formal sin are not to be confused: the latter is the whole sin, the former is an element of formal sin.

427. The essence of sin. — About the essence of sin there has been a celebrated controversy: S. Thomas says that both the material and formal elements pertain to the essence of sin, and accordingly that this consists in something positive; Scotus, on the other hand, Suarez, and others, considering the material element as the mere subject of sin, say that the formal is the whole of sin, and that this consists in a privative, or even, as a few have said, in a negative.

Concerning which it must be noted:

1. It is certain that sin does not consist in a negative: for sin is an evil act, but evil is not the simple absence of a perfection but the absence of a due perfection. Hence sin is essentially not something negative, but at least something privative.

2. It is certain that the formal element of sin is something privative. For the formal of sin is that by which an evil act is evil. Now evil is the privation of good. Therefore the formal of sin is a privation, and sin insofar as it is evil is something privative, namely the privation of conformity with the eternal law or of the rectitude due to the act.

3. It is certain that the sin of omission, considered in its essence separated from the act which is its cause, insofar as it is

mere omission, is something privative, as was said above, n. 419. In it the material is the privation of the due act, the formal the privation of order to the last end.

4. It seems to be said that the essence of the sin of commission is not a pure privation, but something positive, namely that the voluntary act which is the material of sin pertains to the very essence of sin¹. It is proved:

a) Privation is twofold: one is pure, total, and complete, which destroys the whole opposite good, as death, blindness, and therefore can be conceived without any positive, but essentially is only privation; the other is not pure but partial and incomplete, as sickness which is a way to death, and ophthalmia or dim-sightedness to blindness: this does not destroy the whole opposite good but retains something of it so that without this it cannot be conceived, and therefore in its essence includes something positive. But in moral things there is no pure privation (or pure evil), because no will can tend to evil as evil, but always under the aspect of good; the will in acting does not totally take away the good of reason, but always retains something of rectitude or of the order of reason to good. Therefore the privation of due order which is found in sin essentially includes the preservation of some rectitude or tendency to good, which is something positive. Whence, as sickness is not the pure and total privation of life, but includes the partial preservation of life which nevertheless is not acted in the normal way; so sin is not the pure and total privation of the order of reason, but positively includes a tendency or order of reason to an apparent good, which in truth is evil and to be prohibited because it cannot be referred to the last end.

b) Moral good and evil are not opposed contradictorily as quality and privation, thing and nothing, but contrarily as two opposed qualities: for virtue and vice are contraries because they tend to contrary goods or evils; but if vice is contrary to virtue, so also is the sin from which vice is generated or which is elicited by it. But if moral evil or sin were mere privation, it would be opposed to good contradictorily, and would be the simple absence of good. Therefore moral evil or sin is not mere privation but something positive, namely an act tending to an evil object.