Moral theology divides ignorance into a number of categories. The two that will consider here are invincible and vincible. Ignorance is invincible if a person could not remove it by applying reasonable diligence in determining the answer. Ignorance is vincible if a person could remove it by applying reasonable diligence. Reasonable diligence, in turn, is that diligence that a conscientious person would display in seeking the correct answer to a question given (a) the gravity of the question and (b) his particular resources.
The gravity of a question is determined by how great a need the person has to know the answer. The answers to fundamental questions (how to save one’s soul, how to preserve one’s life) have grave weight. The answers to minor questions (the solution to a crossword puzzle) have light weight.
The particular resources a person has include (a) the ease with which he can obtain the information necessary to determine the answer and (b) the ease with which he can make an accurate evaluation of the evidence once it is in his possession. The graver the question and the greater the resources available, the more diligence is needed to qualify as reasonable. The lighter the question and the fewer the resources available, the less diligence is needed to qualify as reasonable.
Just as it is possible to show less than reasonable diligence, it is also possible to show more than reasonable diligence. Diligence can be supererogatory (and praiseworthy) if one shows more diligence than would be expected from an ordinary, conscientious person. Diligence can be excessive or scrupulous (and blameworthy) if someone spends so much time seeking the answer to a particular question that he fails to attend to other matters he should attend to, or if he refuses to come to a conclusion and continues seeking even when he has enough evidence.
Depending on its type and degree, ignorance may remove, diminish, leave unaffected, or even increase one’s culpability for a materially sinful act (cf. CCC 1735, 1746, 1859). Conversely, it may have the same effects on one’s imputability for a materially righteous act. Here we will deal only with the effects of ignorance on one’s culpability for sin,
**Invincible ignorance removes one’s culpability for a materially sinful act, whether one of omission or commission (CCC 1793). **Vincible ignorance may variously affect one’s culpability for a sinful act, depending on the kind of vincibility. If some, but insufficient, diligence was shown toward finding the answer, the ignorance is termed merely vincible. If little or no diligence was shown, the ignorance is termed crass or supine. If one deliberately fostered the ignorance then it is termed affected or *studied. *
If vincible ignorance is merely vincible, crass, or supine, it diminishes culpability for the sinful act relative to the degree of diligence that was shown. If a vincibly ignorant person showed almost reasonable diligence, most of his imputability for the sin could be removed. If he was crassly ignorant, having shown little or no diligence compared to what was reasonable, little or none of his imputability would be removed.
Affected or studied ignorance can increase culpability for a sin, especially if it displays hardness of heart, whereby one would commit the sin irrespective of any law that might exist concerning it. Such an attitude shows contempt for moral law and so increases culpability (cf. CCC 1859).
Potentially, ignorance can diminish or remove imputability for any kind of sin. However, no one is presumed to be ignorant of the principles of moral law since these are written on the heart of every man (CCC 1860). It is possible for a person to be invincibly ignorant that an act is required by natural law. This may be true if the act involves a point that is not obvious, if the person is not mentally quick enough to discern the application of natural law to the case, or if he has been raised to strongly believe in a system that denies the point of natural law. However, such ignorance must be proven, not presumed.
*** A special case is the application of vincible and invincible ignorance to salvation. Failure to embrace the Christian faith (infidelity), total repudiation of the Christian faith (apostasy), and the post-baptismal obstinate denial or willful doubt of particular teachings of the Catholic faith (heresy) are objectively grave sins against the virtue of faith.*** Like any other grave sins, if they are committed with adequate knowledge and deliberate consent, they become mortal sins and will deprive one of salvation.
Also like any other grave sins, their imputability can be removed, diminished, unaffected, or increased by the varying** types of ignorance. **Invincible ignorance removes culpability for the sins against faith, merely vincible ignorance diminishes culpability (sometimes to the point of being venial), crass or supine ignorance will affect culpability for them little or not at all, and hard hearted, affected ignorance will increase culpability for them…
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