QUESTION 76: OF THE CAUSES OF SIN, IN PARTICULAR
We must now consider the causes of sin, in particular, and (1) The
internal causes of sin; (2) its external causes; and (3) sins which are
the causes of other sins. In view of what has been said above (Article ), the
first consideration will be threefold: so that in the first place we
shall treat of ignorance, which is the cause of sin on the part of
reason; secondly, of weakness or passion, which is the cause of sin on
the part of the sensitive appetite; thirdly, of malice, which is the
cause of sin on the part of the will.
Under the first head, there are four points of inquiry:
(1) Whether ignorance is a cause of sin?
(2) Whether ignorance is a sin?
(3) Whether it excuses from sin altogether?
(4) Whether it diminishes sin?
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
Objection 2: Further, causes of sin should be reckoned in respect of sin being
a "turning to" something, as was stated above (Question , Article ). 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
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 (Question , Article ). 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 Cor. 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 (Question , Article , 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.
Article 3: Whether ignorance excuses from sin altogether?
Objection 1: It would seem that ignorance excuses from sin altogether. For as
Augustine says (Retract. i, 9), every sin is voluntary. Now ignorance
causes involuntariness, as stated above (Question , Article ). Therefore ignorance
excuses from sin altogether.
Objection 2: Further, that which is done beside the intention, is done
accidentally. Now the intention cannot be about what is unknown.
Therefore what a man does through ignorance is accidental in human acts.
But what is accidental does not give the species. Therefore nothing that
is done through ignorance in human acts, should be deemed sinful or
Objection 3: Further, man is the subject of virtue and sin, inasmuch as he is
partaker of reason. Now ignorance excludes knowledge which perfects the
reason. Therefore ignorance excuses from sin altogether.
On the contrary, Augustine says (De Lib. Arb. iii, 18) that "some things
done through ignorance are rightly reproved." Now those things alone are
rightly reproved which are sins. Therefore some things done through
ignorance are sins. Therefore ignorance does not altogether excuse from
I answer that, Ignorance, by its very nature, renders the act which it
causes involuntary. Now it has already been stated (Articles ,2) that
ignorance is said to cause the act which the contrary knowledge would
have prevented; so that this act, if knowledge were to hand, would be
contrary to the will, which is the meaning of the word involuntary. If,
however, the knowledge, which is removed by ignorance, would not have
prevented the act, on account of the inclination of the will thereto, the
lack of this knowledge does not make that man unwilling, but not willing,
as stated in Ethic. iii, 1: and such like ignorance which is not the
cause of the sinful act, as already stated, since it does not make the
act to be involuntary, does not excuse from sin. The same applies to any
ignorance that does not cause, but follows or accompanies the sinful act.
On the other hand, ignorance which is the cause of the act, since it
makes it to be involuntary, of its very nature excuses from sin, because
voluntariness is essential to sin. But it may fail to excuse altogether
from sin, and this for two reasons. First, on the part of the thing
itself which is not known. For ignorance excuses from sin, in so far as
something is not known to be a sin. Now it may happen that a person
ignores some circumstance of a sin, the knowledge of which circumstance
would prevent him from sinning, whether it belong to the substance of the
sin, or not; and nevertheless his knowledge is sufficient for him to be
aware that the act is sinful; for instance, if a man strike someone,
knowing that it is a man (which suffices for it to be sinful) and yet be
ignorant of the fact that it is his father, (which is a circumstance
constituting another species of sin); or, suppose that he is unaware that
this man will defend himself and strike him back, and that if he had
known this, he would not have struck him (which does not affect the
sinfulness of the act). Wherefore, though this man sins through
ignorance, yet he is not altogether excused, because, not withstanding,
he has knowledge of the sin. Secondly, this may happen on the part of the
ignorance itself, because, to wit, this ignorance is voluntary, either
directly, as when a man wishes of set purpose to be ignorant of certain
things that he may sin the more freely; or indirectly, as when a man,
through stress of work or other occupations, neglects to acquire the
knowledge which would restrain him from sin. For such like negligence
renders the ignorance itself voluntary and sinful, provided it be about
matters one is bound and able to know. Consequently this ignorance does
not altogether excuse from sin. If, however, the ignorance be such as to
be entirely involuntary, either through being invincible, or through
being of matters one is not bound to know, then such like ignorance
excuses from sin altogether.
Reply to Objection 2: So far as voluntariness remains in the ignorant person, the
intention of sin remains in him: so that, in this respect, his sin is not
Reply to Objection 3: If the ignorance be such as to exclude the use of reason
entirely, it excuses from sin altogether, as is the case with madmen and
imbeciles: but such is not always the ignorance that causes the sin; and
so it does not always excuse from sin altogether.
Article 4: Whether ignorance diminishes a sin?
Objection 1: It would seem that ignorance does not diminish a sin. For that
which is common to all sins does not diminish sin. Now ignorance is
common to all sins, for the Philosopher says (Ethic. iii, 1) that "every
evil man is ignorant." Therefore ignorance does not diminish sin.
Objection 2: Further, one sin added to another makes a greater sin. But
ignorance is itself a sin, as stated above (Article ). Therefore it does not
diminish a sin.
Objection 3: Further, the same thing does not both aggravate and diminish sin.
Now ignorance aggravates sin; for Ambrose commenting on Rm. 2:4, "Knowest
thou not that the benignity of God leadeth thee to penance?" says: "Thy
sin is most grievous if thou knowest not." Therefore ignorance does not
Objection 4: Further, if any kind of ignorance diminishes a sin, this would
seem to be chiefly the case as regards the ignorance which removes the
use of reason altogether. Now this kind of ignorance does not diminish
sin, but increases it: for the Philosopher says (Ethic. iii, 5) that the
"punishment is doubled for a drunken man." Therefore ignorance does not
On the contrary, Whatever is a reason for sin to be forgiven, diminishes
sin. Now such is ignorance, as is clear from 1 Tim. 1:13: "I obtained . .
. mercy . . . because I did it ignorantly." Therefore ignorance
diminishes or alleviates sin.
I answer that, Since every sin is voluntary, ignorance can diminish sin,
in so far as it diminishes its voluntariness; and if it does not render
it less voluntary, it nowise alleviates the sin. Now it is evident that
the ignorance which excuses from sin altogether (through making it
altogether involuntary) does not diminish a sin, but does away with it
altogether. On the other hand, ignorance which is not the cause of the
sin being committed, but is concomitant with it, neither diminishes nor
increases the sin.
Therefore sin cannot be alleviated by any ignorance, but only by such as
is a cause of the sin being committed, and yet does not excuse from the
sin altogether. Now it happens sometimes that such like ignorance is
directly and essentially voluntary, as when a man is purposely ignorant
that he may sin more freely, and ignorance of this kind seems rather to
make the act more voluntary and more sinful, since it is through the
will's intention to sin that he is willing to bear the hurt of ignorance,
for the sake of freedom in sinning. Sometimes, however, the ignorance
which is the cause of a sin being committed, is not directly voluntary,
but indirectly or accidentally, as when a man is unwilling to work hard
at his studies, the result being that he is ignorant, or as when a man
willfully drinks too much wine, the result being that he becomes drunk
and indiscreet, and this ignorance diminishes voluntariness and
consequently alleviates the sin. For when a thing is not known to be a
sin, the will cannot be said to consent to the sin directly, but only
accidentally; wherefore, in that case there is less contempt, and
therefore less sin.
Reply to Objection 1: The ignorance whereby "every evil man is ignorant," is not
the cause of sin being committed, but something resulting from that
cause, viz. of the passion or habit inclining to sin.
Reply to Objection 2: One sin is added to another makes more sins, but it does
not always make a sin greater, since, perchance, the two sins do not
coincide, but are separate. It may happen, if the first diminishes the
second, that the two together have not the same gravity as one of them
alone would have; thus murder is a more grievous sin if committed by a
man when sober, than if committed by a man when drunk, although in the
latter case there are two sins: because drunkenness diminishes the
sinfulness of the resulting sin more than its own gravity implies.
Reply to Objection 3: The words of Ambrose may be understood as referring to
simply affected ignorance; or they may have reference to a species of the
sin of ingratitude, the highest degree of which is that man even ignores
the benefits he has received; or again, they may be an allusion to the
ignorance of unbelief, which undermines the foundation of the spiritual
Reply to Objection 4: The drunken man deserves a "double punishment" for the two
sins which he commits, viz. drunkenness, and the sin which results from
his drunkenness: and yet drunkenness, on account of the ignorance
connected therewith, diminishes the resulting sin, and more, perhaps,
than the gravity of the drunkenness implies, as stated above (ad 2). It
might also be said that the words quoted refer to an ordinance of the
legislator named Pittacus, who ordered drunkards to be more severely
punished if they assaulted anyone; having an eye, not to the indulgence
which the drunkard might claim, but to expediency, since more harm is
done by the drunk than by the sober, as the Philosopher observes (Polit.