§ I. On Ignorance

13. • DEFINITION. Ignorance, taken generally, is the lack of knowledge.

DIVISION. Ignorance is distinguished:

1. Positive or negative, according as it is the lack of knowledge due, or not due, for example, ignorance of canon law in a rustic.

2. Of law, or of fact, according as it is concerned with the existence of a law or of a particular fact.

3. Vincible, or invincible, according as, diligence being applied, it can be overcome, or not. But it is invincible physically, if in no way it can be overcome ¹; morally, however, if, moral diligence being applied, it cannot be removed. That diligence is considered moral which prudent men, according to the gravity of the matter, are accustomed to apply. Moreover, vincible ignorance is not given unless there is known, at least in confusion, an obligation of inquiring further; because the first idea is not in the power of man.

¹ There is no use of this consideration in morals; for nowhere do Theologians inquire whether ignorance is physically, but only whether it is morally, vincible.

Hence mention must also be made of concomitant ignorance, by which someone is ignorant of what he is doing, but would still act, even if he were not ignorant. It in no way influences the act. - Scav.

Vincible ignorance is distinguished as threefold, namely 1. simply such, when some diligence, though not sufficient, is applied to drive it away; 2. crass or supine, when no or scarcely any study is placed in investigating the truth; 3. affected, when someone voluntarily flees the means of laying aside ignorance, lest he be drawn back from his purpose.

Perfect forgetfulness and full inadvertence are to be referred to invincible ignorance. But these, if they are not perfect and proceed from negligence, pertain to vincible ignorance.

4. Antecedent ignorance is that which precedes every will; consequent, however, that which in some way follows it ².

² To the point St. Thomas (I-II, q. 6, art. 8): Ignorance is antecedently related to the will when it is not voluntary, and nevertheless is the cause of willing what otherwise one would not will... And such ignorance causes the involuntary simply.

But ignorance is consequently related to the will insofar as the ignorance itself is voluntary... But since the ignorance itself is voluntary... it cannot cause the involuntary simply; nevertheless it causes the involuntary in a certain respect, insofar as it precedes (that is, causes) the motion of the will toward doing something, which would not be, knowledge being present.

And from these things it is clear that antecedent ignorance is called that which is neither voluntary nor vincible, and thus neither culpable; but consequent ignorance is both voluntary and vincible, and more or less culpable.

14. Principles. - I. Invincible ignorance utterly removes the voluntary, both because it itself is not voluntary, and because nothing can be voluntary where there is no cognition. Therefore no act proceeding from invincible ignorance can be imputed to the agent.

Thus likewise one must determine concerning forgetfulness and perfect inadvertence, since the same reason recurs.

II. Vincible ignorance does not remove the voluntary. For ignorance of this sort, whether directly or indirectly, is truly voluntary. Nevertheless it lessens the voluntary, because it is the cause of willing that which, if it were absent, someone would never will. Say the same also, by parity of reason, concerning imperfect forgetfulness and inadvertence.

III. Crass ignorance and affected ignorance much less lessen the voluntary, and consequently sin. The reason is that the former arises from grave negligence, but the latter is retained deliberately for sinning more freely.

You Will Resolve. - 1. A spouse sinning with a woman whom he invincibly does not know to be the sister of his wife is guilty of adultery, but not of incest, as being invincibly ignorant of it.

2. Children who have done things illicit in themselves without any anguish of conscience or suspicion of malice, in reality have not sinned formally, even if they have already attained the use of reason; and therefore afterward they are not held to confess them, when they understand that they are illicit, since material sins are not matter of confession.

3. If a confessor or judge notices that he lacks sufficient knowledge for discharging his office as is fitting, and neglects to acquire the knowledge, or before he acquires it proceeds to exercise his function, he will be held for the errors which in some way at least he foresaw, because they are voluntary to him, at least in the cause.

4. If negligence in laying aside ignorance is culpable only venially, the deed following from it will be imputable only unto venial fault. The reason is that acts of this kind are voluntary, and thus culpable, only in the cause; therefore, since the cause, namely ignorance, does not reach grave fault, the effect also cannot exceed light fault.

See many other things on ignorance elsewhere passim, especially in the treatise on Conscience, on Laws, on Sins, and on Contracts in general, where error is treated. - See Cases, vol. I, no. 12 and following.