The Problem of Ignorance
Intimately connected to the question of prudence, its cultivation, and its exercise, as well as to the earlier questions of conscience and freedom, is the problem of ignorance, for ignorance is destructive of all three.
If we are called to freedom, then we are first and foremost called to know the truth: “Ye shall know the truth, and the truth shall set you free.” We are given no reason to believe that freedom can exist apart from this truth. Therefore, to the degree that we lack the truth—which is to say, to the degree that we live in ignorance—we are not really free. Because of this, we can say that it is our responsibility to minimize and dispel ignorance whenever we can. We can also infer that we will be held responsible when our ignorance is of the sort that could have easily been dispelled but which, for whatever reason, we allowed to persist.
a. Two kinds of ignorance
Although ignorance is undesirable, it is also unavoidable, as our mental capacities are finite. However, since it is obvious from what has been said above that, to some extent, we are responsible for our ignorance, then we arrive at a twofold division of ignorance: the first is known as invincible ignorance, and this is the kind of ignorance for which we are not morally responsible. The second is called vincible ignorance because it refers to a condition of ignorance which could have been removed if only the individual had taken the proper steps to remove it. Further comment on each of these is necessary in order to flesh out the distinction.
b. Invincible ignorance
We are all of us born ignorant of just about everything, and even if we live diligently we will still have a lot to learn by the time we die. The natural consequence of this inevitable state of ignorance is that we will constantly make mistakes due to our lack of knowledge of the truth. In fact, it might be legitimate to say that man in general, insofar as he is fallen, is more often separated from God due to ignorance than to evil plain and simple, and that the sins a man commits are more often the result of wrong-headedness than hard-heartedness. According to Pope Leo XIII:
“It is rather ignorance than ill-will which keeps multitudes away from Jesus Christ. There are many who study humanity and the natural world; few who study the Son of God. The first step, then, is to substitute knowledge for ignorance, so that He may no longer be despised or rejected because He is unknown.”
Observing this, and considering the fact that a man cannot be held responsible for a sin in which his will gave no real assent, we can say that this inevitable, invincible sort of ignorance is not a sin. However, there is an underlying assumption that goes along with this notion of invincible ignorance, which is that we have at the same time done our best to overcome it and minimize its impact on our lives.
c. Vincible ignorance
Now we must look at the other side of the picture. When a person “takes little trouble to find out what is true and good, or when conscience is almost blinded through the habit of committing sin,” then we can hardly say that his ignorance (and whatever actions stem from it) are “inevitable.” In these cases we must admit that due to his own choices (mental sloth or habitual sin) his ignorance is vincible and that he is to some degree responsible for it. In short, he could have had the light, but chose the darkness instead. This means that if we are too lazy to educate our conscience and participate in its formation, it will naturally become deformed, and this state of things will be our own fault. Likewise, if we allow ourselves to live in constant sin, our consciences will be desensitized and our judgment thrown askew. In such circumstances, we are clearly responsible for our negligence.
 Jn 8:32.