Summa summae S. Thomae, Tomus II

St. Thomas, q. 86.

What we call habitual sin the ancients called stain; for, as authors note, this complex term, habitual sin, is not found among the ancients, but only stain. That habitual sin and stain are one and the same is manifest; because to be stained and unclean before God is to be defiled with sins, injurious and offensive to God, which is the proper and formal effect of habitual sin.

I say 1°: From actual sin there follows in the soul a stain which is called habitual sin¹.

The Scriptures prove this effect of sin, calling sin by its proper name stain, as Josue, XXII, 17: Is it a small thing unto you that you sinned against Beelphegor, and that even to this day the stain of that crime remaineth in you? Likewise Jerem., II, 22, Psal., XIV, 2, and elsewhere. Also those which call sins filthinesses, uncleannesses, defilements, as Isa., IV, 4: If the Lord shall wash away the filth of the daughters of Sion.

Reason also supports it. Stain in spiritual things is said after the manner of stain in bodily things². Therefore just as a clean body is said properly to be stained when from contact with another body it loses its brightness, as when a garment is infected with oil; so the soul is said metaphorically to be stained, when through disordered affection toward creatures, which is a certain touch of hers, she loses the brightness she had from the refulgence of the light both of reason and of grace. For each thing, as it is perfected by union with nobler things, so is it disfigured and made vile by admixture with inferiors: thus silver by admixture of gold becomes better, by admixture of tin deteriorates and becomes impure.

I say 2°: The stain remains in the soul after the act of sin³.

It is proved 1° from the places cited in the first conclusion, and because man, according to Scripture, after the act of sin is called and remains a sinner. Matth., IX, 10: Sinners and publicans coming sat down with Jesus. Therefore something remains in him whereby he be so denominated; otherwise he would be denominated sinner by merely extrinsic denomination, which we shall impugn presently.

2° By reason. Man incurs the stain of sin by recession from the light of reason and of divine law⁴. Therefore, as long as man remains outside such light, he remains under the stain of sin. — I subjoin. Yet although the act of sin whereby man departed from the light of reason and divine law ceases, he does not at once return to that in which he had been, but some motion of will contrary to the first motion is required; as if one be distant from something through some motion, he does not at once, the motion ceasing, become near to it, but he must approach, returning through a contrary motion. Therefore.

I say 3°: The stain of mortal sin is the privation of the brightness of grace, or, what is the same, of grace itself, connoting the preceding actual sin from which it is caused.

The first part is proved. 1° The stain of sin, or habitual sin, consists in that which is first expelled per se by justification; for justification is remission of sins. But the privation of sanctifying grace is that which is first expelled by justification. « [For] remission of guilt cannot be understood if infusion of grace were not present, » as the Author teaches infra q. 113, a. 2, c, and as Trid. says, sess. VI, cap. 7: Grace, or « the justice of God, is the one formal cause of our justification. » Therefore.

2° By that man is constituted habitually a sinner and unjust, by whose opposite he is constituted habitually just. But man is constituted habitually just by sanctifying grace. Therefore by its privation he is constituted habitually unjust and a sinner.

The second part is proved. 1° That that stain have the reason of guilt, it must be moral and voluntary. Therefore it must connote the act of will from which it is caused.

2° If the stain consisted in privation of sanctifying grace without respect to the actual sin from which it is caused, since the privation of such grace is unique, indivisible, and of the same species in all, it cannot be explained how stains are many, diverse and unequal⁵.

I say 4°: The stain of venial sin is the privation of the fervor of charity from actual venial sins.

St. Thomas expounds and explains this conclusion in IV Sentent., dist. 16, q. 2, a. 2, ad 1, in these words: « It must be said that stain can be in a twofold way: in one mode, through privation of beauty; and thus in venial sin no stain remains, because it does not take away grace, which is the adornment of the soul: in another mode, through this, that the beauty, which is of grace, is hindered from appearing outwardly, as by dust the beauty of the face is befouled; and such stain is in venial sin, because the adornment of grace is hindered from being shown outwardly in acts. »

Whence the stain of venial sin is not a stain properly and simply, but only secundum quid; because it does not take away the form whereby beauty inheres in the soul, namely grace, but only obscures and covers it, that it shine less in acts; as a comely face by dust becomes somewhat uncleanly, yet its beauty is not destroyed⁶.