Invincible ignorance is used in Catholic moral theology to refer to the state of persons (such as pagans and infants) who are ignorant of the Christian message because they have not yet had an opportunity to hear it.
Vincible ignorance is, in Catholic moral theology, ignorance that a person could remove by applying reasonable diligence in the given set of circumstances. It contrasts with invincible ignorance, which a person is either entirely incapable of removing, or could only do so by supererogatory efforts (i.e., efforts above and beyond normal duty). An example of vincible ignorance would be a person who is unsure about certain Catholic teachings, but refrains from seeking an explanation of those teachings.
It is culpable to remain willfully ignorant of matters that one is obligated to know. While invincible ignorance eliminates culpability, vincible ignorance at most mitigates it, and may even aggravate guilt. The guilt of an action performed in vincible ignorance ought to be measured by the degree of diligence or negligence shown in performing the act. An individual is morally responsible for their ignorance and for the acts resulting from it. If some insufficient diligence was shown in dispelling ignorance, it is termed merely vincible; it may diminish culpability to the point of rendering a sin venial. When little or no effort is made to remove ignorance, the ignorance is termed crass or supine; it removes little or no guilt. Deliberately fostered ignorance is affected or studied; it can increase guilt.
Ignorance may be:
Of law, when one is unaware of the existence of the law itself, or at least that a particular case is comprised under its provisions.
Of fact, when not the relation of something to the law but the thing itself or some circumstance is unknown.
Of penalty, when a person is not cognizant that a sanction has been attached to a particular crime. This is especially to be considered when there is question of more serious punishment.