Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that ignorance excuses from sin altogether. For as Augustine says (Retract. i, 9), every sin is voluntary. Now ignorance causes involuntariness, as stated above (Question 6, Article 8). Therefore ignorance excuses from sin altogether.

Objection 2: Further, that which is done beside the intention, is done accidentally. Now the intention cannot be about what is unknown. Therefore what a man does through ignorance is accidental in human acts. But what is accidental does not give the species. Therefore nothing that is done through ignorance in human acts, should be deemed sinful or virtuous.

Objection 3: Further, man is the subject of virtue and sin, inasmuch as he is partaker of reason. Now ignorance excludes knowledge which perfects the reason. Therefore ignorance excuses from sin altogether.

On the contrary, Augustine says (De Lib. Arb. iii, 18) that "some things done through ignorance are rightly reproved." Now those things alone are rightly reproved which are sins. Therefore some things done through ignorance are sins. Therefore ignorance does not altogether excuse from sin.

I answer that, Ignorance, by its very nature, renders the act which it causes involuntary. Now it has already been stated (Articles 1,2) that ignorance is said to cause the act which the contrary knowledge would have prevented; so that this act, if knowledge were to hand, would be contrary to the will, which is the meaning of the word involuntary. If, however, the knowledge, which is removed by ignorance, would not have prevented the act, on account of the inclination of the will thereto, the lack of this knowledge does not make that man unwilling, but not willing, as stated in Ethic. iii, 1: and such like ignorance which is not the cause of the sinful act, as already stated, since it does not make the act to be involuntary, does not excuse from sin. The same applies to any ignorance that does not cause, but follows or accompanies the sinful act.

On the other hand, ignorance which is the cause of the act, since it makes it to be involuntary, of its very nature excuses from sin, because voluntariness is essential to sin. But it may fail to excuse altogether from sin, and this for two reasons. First, on the part of the thing itself which is not known. For ignorance excuses from sin, in so far as something is not known to be a sin. Now it may happen that a person ignores some circumstance of a sin, the knowledge of which circumstance would prevent him from sinning, whether it belong to the substance of the sin, or not; and nevertheless his knowledge is sufficient for him to be aware that the act is sinful; for instance, if a man strike someone, knowing that it is a man (which suffices for it to be sinful) and yet be ignorant of the fact that it is his father, (which is a circumstance constituting another species of sin); or, suppose that he is unaware that this man will defend himself and strike him back, and that if he had known this, he would not have struck him (which does not affect the sinfulness of the act). Wherefore, though this man sins through ignorance, yet he is not altogether excused, because, not withstanding, he has knowledge of the sin. Secondly, this may happen on the part of the ignorance itself, because, to wit, this ignorance is voluntary, either directly, as when a man wishes of set purpose to be ignorant of certain things that he may sin the more freely; or indirectly, as when a man, through stress of work or other occupations, neglects to acquire the knowledge which would restrain him from sin. For such like negligence renders the ignorance itself voluntary and sinful, provided it be about matters one is bound and able to know. Consequently this ignorance does not altogether excuse from sin. If, however, the ignorance be such as to be entirely involuntary, either through being invincible, or through being of matters one is not bound to know, then such like ignorance excuses from sin altogether.

Reply to Objection 1: Not every ignorance causes involuntariness, as stated above (Question 6, Article 8). Hence not every ignorance excuses from sin altogether.

Reply to Objection 2: So far as voluntariness remains in the ignorant person, the intention of sin remains in him: so that, in this respect, his sin is not accidental.

Reply to Objection 3: If the ignorance be such as to exclude the use of reason entirely, it excuses from sin altogether, as is the case with madmen and imbeciles: but such is not always the ignorance that causes the sin; and so it does not always excuse from sin altogether.

Articulus 3

Argumentum 1

Ad tertium sic proceditur. Videtur quod ignorantia, ex toto excuset a peccato.

Quia, ut Augustinus dicit, omne peccatum voluntarium est.

Sed ignorantia causat involuntarium ut supra habitum est.

Ergo ignorantia totaliter excusat peccatum.

Argumentum 2

Praeterea, id quod aliquis facit praeter intentionem, per accidens agit. Sed intentio non potest esse de eo quod est ignotum. Ergo id quod per ignorantiam homo agit, per accidens se habet in actibus humanis. Sed quod est per accidens, non dat speciem. Nihil ergo quod est per ignorantiam factum, debet iudicari peccatum vel virtuosum in humanis actibus.

Argumentum 3

Praeterea, homo est subiectum virtutis et peccati inquantum est particeps rationis. Sed ignorantia excludit scientiam, per quam ratio perficitur. Ergo ignorantia totaliter excusat a peccato.

Sed Contra

Sed contra est quod Augustinus dicit, in libro de Lib. Arb., quod quaedam per ignorantiam facta, recte improbantur.

Sed solum illa recte improbantur quae sunt peccata.

Ergo quaedam per ignorantiam facta, sunt peccata.

Non ergo ignorantia omnino excusat a peccato.

Corpus

Respondeo dicendum quod ignorantia de se habet quod faciat actum quem causat, involuntarium esse.

Iam autem dictum est quod ignorantia dicitur causare actum quem scientia opposita prohibebat. Et ita talis actus, si scientia adesset, esset contrarius voluntati, quod importat nomen involuntarii. Si vero scientia quae per ignorantiam privatur, non prohiberet actum, propter inclinationem voluntatis in ipsum; ignorantia huius scientiae non facit hominem involuntarium, sed non volentem, ut dicitur in III ethic..

Et talis ignorantia, quae non est causa actus peccati, ut dictum est, quia non causat involuntarium, non excusat a peccato. Et eadem ratio est de quacumque ignorantia non causante, sed consequente vel concomitante actum peccati. Sed ignorantia quae est causa actus, quia causat involuntarium, de se habet quod excuset a peccato, eo quod voluntarium est de ratione peccati. Sed quod aliquando non totaliter excuset a peccato, potest contingere ex duobus. Uno modo, ex parte ipsius rei ignoratae.

Intantum enim ignorantia excusat a peccato, inquantum ignoratur aliquid esse peccatum. Potest autem contingere quod aliquis ignoret quidem aliquam circumstantiam peccati, quam si sciret, retraheretur a peccando, sive illa circumstantia faciat ad rationem peccati sive non; et tamen adhuc remanet in eius scientia aliquid per quod cognoscit illud esse actum peccati.

Puta si aliquis percutiens aliquem, sciat quidem ipsum esse hominem, quod sufficit ad rationem peccati; non tamen scit eum esse patrem, quod est circumstantia constituens novam speciem peccati; vel forte nescit quod ille se defendens repercutiat eum, quod si sciret, non percuteret, quod non pertinet ad rationem peccati.

Unde licet talis propter ignorantiam peccet, non tamen totaliter excusatur a peccato, quia adhuc remanet ei cognitio peccati. Alio modo potest hoc contingere ex parte ipsius ignorantiae, quia scilicet ipsa ignorantia est voluntaria, vel directe, sicut cum aliquis studiose vult nescire aliqua, ut liberius peccet; vel indirecte, sicut cum aliquis propter laborem, vel propter alias occupationes, negligit addiscere id per quod a peccato retraheretur. Talis enim negligentia facit ignorantiam ipsam esse voluntariam et peccatum, dummodo sit eorum quae quis scire tenetur et potest. Et ideo talis ignorantia non totaliter excusat a peccato. Si vero sit talis ignorantia quae omnino sit involuntaria, sive quia est invincibilis, sive quia est eius quod quis scire non tenetur; talis ignorantia omnino excusat a peccato.

Ad 1

Ad primum ergo dicendum quod non omnis ignorantia causat involuntarium, sicut supra dictum est.

Unde non omnis ignorantia totaliter excusat a peccato.

Ad 2

Ad secundum dicendum quod inquantum remanet in ignorante de voluntario, intantum remanet de intentione peccati.

Et secundum hoc, non erit per accidens peccatum.

Ad 3

Ad tertium dicendum quod, si esset talis ignorantia quae totaliter usum rationis excluderet, omnino a peccato excusaret, sicut patet in furiosis et amentibus. Non autem semper ignorantia causans peccatum est talis.

Et ideo non semper totaliter excusat a peccato.