Summa summae S. Thomae, Tomus II

I say : Invincible ignorance of the law of nature excuses from formal sin the one acting from it. This is against Luther, Calvin, Jansenius and the Jansenists, defined by Alexander VIII, 7 December 1690, in the condemnation of this proposition: « Even if invincible ignorance of the law of nature be granted, in the state of fallen nature it does not excuse from formal sin the one acting from it. » It is the second among 31.

It is proved 1° from Sts. Augustine and Thomas. Aug., lib. III, de lib. Arbit., cap. 18, n. 50: « Is there so great a deceit [of ignorance] that it can by no means be guarded against? If it is so, there are no sins. » St. Thomas, here q. 76, a. 3, c, speaking of invincible ignorance in general, expressly says: « But if it be such ignorance as is altogether involuntary, either because it is invincible, or because it concerns what one is not bound to know, such ignorance altogether excuses from sin. »

It is proved 2° by this fundamental reasoning of St. Thomas. That which takes away from the act the character of the voluntary, and renders it involuntary, excuses from formal sin; for sin is a moral act, consequently free and voluntary. But this is what invincible ignorance of the law of nature effects; for the voluntary is defined as « that which is from an intrinsic principle with knowledge of the end ». Therefore.

They answer that invincible ignorance of the law of nature, and the things done from it, are voluntary in us in Adam, since they are effects of that sin.

On the contrary : 1° For personal sin there does not suffice the voluntary of nature, or in the head, but there is required the voluntary of the person, as Alexander VIII defined in the condemnation of this proposition: « In the state of fallen nature, for mortal sin and demerit there suffices that liberty by which it was free and voluntary in its cause, original sin and the will of Adam sinning. » It is the first among the condemned propositions (7 December 1690). 2° Because otherwise it would follow that the indeliberate motions of concupiscence which we suffer unwillingly, all the defects and miseries of this life, folly, frenzy, blindness, etc., and all the things that arise from these, would be formal sins; because they too are effects of original sin and voluntary in Adam.

It is confirmed. Invincible ignorance of positive law, even divine law, excuses from formal sin the one acting from it, the adversaries themselves confessing. Therefore also invincible ignorance of the law of nature. — Proof from consequence. Invincible ignorance of positive law excuses from formal sin because it itself is involuntary, and what is done from it is involuntary. But likewise invincible ignorance of the law of nature itself is involuntary, and what is done from it is involuntary. Therefore.

For the solution of the objections from Augustine, whom the Jansenists press most of all, it must be observed that in all the things objected from him the holy Doctor never speaks of ignorance of the natural law, but either determinately of ignorance of positive law, or generally of ignorance of whatever kind of law; whence these are to be solved by them, as by us. It must therefore be said that, when St. Augustine says that ignorance of the law does not excuse from sin, he speaks either of vincible and indirectly voluntary ignorance through negligence in learning, or of sin taken in a wide sense, for that which is from sin and leads on to sin, as it is taken by the Apostle and by the council of Trid., sess. V, can. 2. « Not only that do we call sin, he says, lib. III de libero Arbit., c. 19, n. 54, which is properly called sin, for it is committed by free will and knowingly; but also that which now follows necessarily from the punishment of this. »