Prima Secundæ, Question 76 — Summa Theologiae
Article 1. Whether ignorance can be a cause of sin?
Objection 1. It would seem that ignorance cannot be a cause of sin: because a non-being is not the cause of anything. Now ignorance is a non-being, since it is a privation of knowledge. Therefore ignorance is not a cause of sin.
Objection 2. Further, causes of sin should be reckoned in respect of sin being a “turning to” something, as was stated above (I-II:75:1). Now ignorance seems to savor of “turning away” from something. Therefore it should not be reckoned a cause of sin.
Objection 3. Further, every sin is seated in the will. Now the will does not turn to that which is not known, because its object is the good apprehended. Therefore ignorance cannot be a cause of sin.
On the contrary, Augustine says (De Nat. et Grat. lxvii) “that some sin through ignorance.”
I answer that, According to the Philosopher (Phys. viii, 27) a moving cause is twofold, direct and indirect. A direct cause is one that moves by its own power, as the generator is the moving cause of heavy and light things. An indirect cause, is either one that removes an impediment, or the removal itself of an impediment: and it is in this way that ignorance can be the cause of a sinful act; because it is a privation of knowledge perfecting the reason that forbids the act of sin, in so far as it directs human acts.
Now we must observe that the reason directs human acts in accordance with a twofold knowledge, universal and particular: because in conferring about what is to be done, it employs a syllogism, the conclusion of which is an act of judgment, or of choice, or an operation. Now actions are about singulars: wherefore the conclusion of a practical syllogism is a singular proposition. But a singular proposition does not follow from a universal proposition, except through the medium of a particular proposition: thus a man is restrained from an act of parricide, by the knowledge that it is wrong to kill one’s father, and that this man is his father. Hence ignorance about either of these two propositions, viz. of the universal principle which is a rule of reason, or of the particular circumstance, could cause an act of parricide. Hence it is clear that not every kind of ignorance is the cause of a sin, but that alone which removes the knowledge which would prevent the sinful act. Consequently if a man’s will be so disposed that he would not be restrained from the act of parricide, even though he recognized his father, his ignorance about his father is not the cause of his committing the sin, but is concomitant with the sin: wherefore such a man sins, not “through ignorance” but “in ignorance,” as the Philosopher states (Ethic. iii, 1).
Reply to Objection 1. Non-being cannot be the direct cause of anything: but it can be an accidental cause, as being the removal of an impediment.
Reply to Objection 2. As knowledge, which is removed by ignorance, regards sin as turning towards something, so too, ignorance of this respect of a sin is the cause of that sin, as removing its impediment.
Reply to Objection 3. The will cannot turn to that which is absolutely unknown: but if something be known in one respect, and unknown in another, the will can will it. It is thus that ignorance is the cause of sin: for instance, when a man knows that what he is killing is a man, but not that it is his own father; or when one knows that a certain act is pleasurable, but not that it is a sin.
Article 2. Whether ignorance is a sin?
Objection 1. It would seem that ignorance is not a sin. For sin is “a word, deed or desire contrary to God’s law,” as stated above (I-II:71:5). Now ignorance does not denote an act, either internal or external. Therefore ignorance is not a sin.
Objection 2. Further, sin is more directly opposed to grace than to knowledge. Now privation of grace is not a sin, but a punishment resulting from sin. Therefore ignorance which is privation of knowledge is not a sin.
Objection 3. Further, if ignorance is a sin, this can only be in so far as it is voluntary. But if ignorance is a sin, through being voluntary, it seems that the sin will consist in the act itself of the will, rather than in the ignorance. Therefore the ignorance will not be a sin, but rather a result of sin.
Objection 4. Further, every sin is taken away by repentance, nor does any sin, except only original sin, pass as to guilt, yet remain in act. Now ignorance is not removed by repentance, but remains in act, all its guilt being removed by repentance. Therefore ignorance is not a sin, unless perchance it be original sin.
Objection 5. Further, if ignorance be a sin, then a man will be sinning, as long as he remains in ignorance. But ignorance is continual in the one who is ignorant. Therefore a person in ignorance would be continually sinning, which is clearly false, else ignorance would be a most grievous sin. Therefore ignorance is not a sin.
On the contrary, Nothing but sin deserves punishment. But ignorance deserves punishment, according to 1 Corinthians 14:38: “If any man know not, he shall not be known.” Therefore ignorance is a sin.
I answer that, Ignorance differs from nescience, in that nescience denotes mere absence of knowledge; wherefore whoever lacks knowledge about anything, can be said to be nescient about it: in which sense Dionysius puts nescience in the angels (Coel. Hier. vii). On the other hand, ignorance denotes privation of knowledge, i.e. lack of knowledge of those things that one has a natural aptitude to know. Some of these we are under an obligation to know, those, to wit, without the knowledge of which we are unable to accomplish a due act rightly. Wherefore all are bound in common to know the articles of faith, and the universal principles of right, and each individual is bound to know matters regarding his duty or state. Meanwhile there are other things which a man may have a natural aptitude to know, yet he is not bound to know them, such as the geometrical theorems, and contingent particulars, except in some individual case. Now it is evident that whoever neglects to have or do what he ought to have or do, commits a sin of omission. Wherefore through negligence, ignorance of what one is bound to know, is a sin; whereas it is not imputed as a sin to man, if he fails to know what he is unable to know. Consequently ignorance of such like things is called “invincible,” because it cannot be overcome by study. For this reason such like ignorance, not being voluntary, since it is not in our power to be rid of it, is not a sin: wherefore it is evident that no invincible ignorance is a sin. On the other hand, vincible ignorance is a sin, if it be about matters one is bound to know; but not, if it be about things one is not bound to know.
Reply to Objection 1. As stated above (I-II:71:6 ad 1), when we say that sin is a “word, deed or desire,” we include the opposite negations, by reason of which omissions have the character of sin; so that negligence, in as much as ignorance is a sin, is comprised in the above definition of sin; in so far as one omits to say what one ought, or to do what one ought, or to desire what one ought, in order to acquire the knowledge which we ought to have.
Reply to Objection 2. Although privation of grace is not a sin in itself, yet by reason of negligence in preparing oneself for grace, it may have the character of sin, even as ignorance; nevertheless even here there is a difference, since man can acquire knowledge by his acts, whereas grace is not acquired by acts, but by God’s favor.
Reply to Objection 3. Just as in a sin of transgression, the sin consists not only in the act of the will, but also in the act willed, which is commanded by the will; so in a sin of omission not only the act of the will is a sin, but also the omission, in so far as it is in some way voluntary; and accordingly, the neglect to know, or even lack of consideration is a sin.
Reply to Objection 4. Although when the guilt has passed away through repentance, the ignorance remains, according as it is a privation of knowledge, nevertheless the negligence does not remain, by reason of which the ignorance is said to be a sin.
Reply to Objection 5. Just as in other sins of omission, man sins actually only at the time at which the affirmative precept is binding, so is it with the sin of ignorance. For the ignorant man sins actually indeed, not continually, but only at the time for acquiring the knowledge that he ought to have.