“Voluntary acts demand an interiority which is characterized by knowledge of the end and the reason why the end is the end, and the means which is the result of intellectual knowledge.” In other words, “The first requirement for moral responsibility is that the action result from a movement within and not from a movement outside man.”
Free will, therefore, is a requirement for culpability and merit. If there is no freedom, no true human action, there can be no responsibility imputed to that action. A stone has only its nature (given to it from outside) and forces of its environment (also outside). Therefore, it cannot be blamed for its actions. We do not blame the rock that strikes the man, but the one who threw it. We implicitly realize this truth of voluntary action and responsibility.
Voluntary action is found in the Will. The will is determined to the good, but only goodness itself compels it. All other goods are presented to it as limited, for goods are good in one way and not in another. Only goodness itself has no aspect of it which can be seen as not good. This is why St. Augustine can say “the one who knows You and other things is no happier for knowing created things and You than for knowing You alone.” (Augustine, Confessions)
So the will is presented objects as good by the intellect which recognizes truth, but the will is free to choose or reject these, because all, including God as known before the beatific vision, are presented as limited goods.
As has been said, the will can accept or deny only what the intellect has presented to it. In other words, nothing can be willed unless first known. Obviously, then, ignorance in the intellect prevents the will from moving toward or away from an object, because it does not know it or does not know it as it really is.
The will, however, does have a place in whether or not it knows of the object to which it should strive. One can be culpable for their ignorance if they could reasonably be expect to seek the truth in reference to the object. For example, there are those who do not know that the Catholic Church is the fullness of the truth as established by Christ. These people are termed invincibly ignorant, as the Catechism states:
If – on the contrary – the ignorance is invincible, or the moral subject is not responsible for his erroneous judgment, the evil committed by the person cannot be imputed to him. It remains no less an evil, a privation, a disorder. One must therefore work to correct the errors of moral conscience. (CCC 1793)
However, not all ignorance is excused:
Yet it can happen that moral conscience remains in ignorance and makes erroneous judgments about acts to be performed or already committed. This ignorance can often be imputed to personal responsibility. This is the case when a man “takes little trouble to find out what is true and good, or when conscience is by degrees almost blinded through the habit of committing sin.” In such cases, the person is culpable for the evil he commits. (CCC 1790-1791)
In the end, only God can judge for certain the culpability of each man’s ignorance. But we must remember that “the truth will set you free,” and thus “One must therefore work to correct the errors of moral conscience.” (CCC 1793)
Passions likewise affect our will. In and of themselves, they are neutral, neither good nor bad. Virtue brings them under the control of reason. They can either increase or decrease our culpability or merit, depending upon how they affect the decisions of the will.
For example, if one were to walk in and discover his wife in an adulterous affair, his immediate reaction with the passion of anger will likely include less culpability for the action performed than it would if he pondered the situation and later went and did the same thing to her or the lover. In the rising of the passion of anger, and because of the relation of the body to the mind, the reasoning ability of the man in that instance is confused, and not all is taken into account. The man who ponders a cold blooded killing, however, is more culpable, even if the circumstances and the object of the act were the same.
Circumstance also has an affect on the choices chosen by the will. They are, “in the philosophically sense, accidents to determining how an action relates to reason.” Circumstances can affect the morality of an act in three ways. They can change the kind of act objectively speaking, can change the gravity of the act, and can affect the subject’s involvement in the committing of the deed itself.
Circumstances are subjective to the person committing the act and the situation in which it is committed, but the blame or praise given the acting subject is increased or decreased in as much as the person doing the action has knowledge of the circumstances and commits or omits the act in light of this.
For example, if I have but one meal with me, and give it away to the poor, the action maybe the same as a rich man giving one meal away that day, but the circumstances of the rich man and myself, being different, affect the praise or blame of the act, assuming there are not other factors such as my seeking personal praise for having done so or some favor in return, etc.
In brief, ignorance, the passions, and circumstances all affect the freedom of man because each alters his subjective position and his culpability in knowing or not knowing the full extent of the application of the principles he knows to the particular situation at hand.