Question Sixteen: Synderesis

Is synderesis a power or a habit?
Can synderesis err (peccare)?
Are there some in whom synderesis is extinguished?


The question treats of synderesis

and in the first place we ask:

Is synderesis a power or a habit?

[Parallel readings: II Sent., 24, 2, 3; S.T., I, 79, 12.]


It seems to be a power, for

1. Parts resulting from the same division belong to the same genus. But, as Jerome says, synderesis is differentiated from reason, the concupiscent, and the irascible. Therefore, since the irascible, the concupiscent, and reason are powers, synderesis will also be a power.

2. It was said that synderesis does not denote a power alone, but an habituated power.—On the contrary, a subject with an accident is not divided from a subject alone. For a division of animals into man and white man would be improper. Therefore, since a habit is related to a power as an accident to its subject, it does not seem that that which denotes a power alone, as reason, the irascible, and the concupiscent, can be fittingly divided from that which denotes an habituated power.

3. The same power may have different habits. Therefore, if one power is distinguished from another by reason of a habit, the division in which the parts of the soul are distinguished from each other ought to have as many members as there are habits of the powers.

4 One and the same thing cannot be regulator and that which is regulated. But a power is regulated by its habit. Therefore, a power and a habit cannot so blend into one thing that one name will at the same time denote the power and the habit.

5. Nothing is inscribed in a habit, but only in a power. But the general principles of law are said to be inscribed in synderesis. Therefore, it denotes a power without qualification.

6. One thing cannot arise from two things unless one of the two is changed. But the natural habit which the name synderesis is said to represent is not changed, since what is natural must be permanent. Neither are the faculties of the soul changed. Therefore, it seems that one thing cannot result from a habit and a faculty so that both can be given the one name.

7. Synderesis is opposed to sensuality, for, as sensuality always inclines to evil, so synderesis always inclines to good. But sensuality is simply a faculty without a habit. Therefore synderesis denotes simply a faculty.

8. As is said in the Metaphysics, the nature which the name signifies is the definition. Therefore, that which is not one in such a way that it can be defined, cannot be signified by one name. Rather, it is a combination made up of a subject and an accident. Thus, when I say “white man,” it cannot be defined, as is proved in the Metaphysics. The same is true of the combination of a power and a habit. Consequently, a power together with a habit cannot be denoted by one name.

9. Higher reason is the name of a power alone. But synderesis seems to be the same thing as higher reason. For, as Augustine says, in the seat of natural judgment, which we call synderesis, “there are certain rules and lights of the virtues, and things true and things unchangeable.” However, it belongs to higher reason, according to Augustine, to grasp unchangeable natures. Therefore, synderesis is simply a power.

10. According to the Philosopher, everything that is in the soul is either a power, a habit, or a passion. Therefore, either the division of the Philosopher is inadequate or there is nothing in the soul which is at once a power and a habit.

11. Opposites cannot exist in the same thing. But we have an innate tendency (fomes) which always inclines to evil. Therefore, there cannot be in us a habit which always inclines to good. Thus, synderesis, which always inclines to good, is not a habit, nor an habituated power, but simply a power.

12. A power and a habit suffice for activity. Therefore, if synderesis is a power with an innate habit, since synderesis inclines to good, man will be capable of performing good actions by reason of purely natural gifts. But this seems to be the heresy of Pelagius.

13 If synderesis is an habituated power, it will not be a passive power but an active one, since it will have some activity. Moreover, just as a passive power is rooted in matter, so an active power is rooted in a form. But in the human soul there is a twofold form: one through which it corresponds to the angels, in so far as it is a spirit, and this is the higher form; and another, the lower form, through which it gives life to the body, in so far as it is a soul. Therefore, synderesis must be based on the higher or the lower form. If on the higher, it is higher reason; if on the lower, it is lower reason. But both higher and lower reason designate simply a power. Therefore, synderesis is simply a power.

14. If synderesis denotes an habituated power, the habit must be innate. For, if it were an acquired or an infused habit, it would be possible to lose synderesis. But synderesis does not denote an innate habit. Therefore, it signifies simply a power. We prove the minor in this way. Every habit which presupposes an act [prior] in time is not an innate habit. But synderesis presupposes an act [prior] in time, for it belongs to synderesis to speak out against evil and stir on to good. And this could not take place unless good and evil are actually known beforehand. Therefore, synderesis requires an act [prior] in time.

15. The function of synderesis seems to be to make judgments. Hence it is called the natural seat of judgment. But free choice takes its name from judging. Therefore, free choice is the same as synderesis. But free choice is simply a power. Therefore, so is synderesis.

16. If synderesis is an habituated power, a kind of composite of the two, it will not be such by logical composition, by which a species is composed of genus and difference, for a power is not related to a habit as genus to difference. For, thus, any habit added to a power would constitute a distinct power. Therefore, it is natural composition. But in natural composition the compound is different from the elements that make it up, as is proved in the Metaphysics. Therefore, synderesis is neither a power nor a habit, but something else. But this cannot be. Therefore, it remains that it is simply a power.

To the Contrary

1. If synderesis is a power, it must be a power of reason. But the powers of reason are directed to opposites. Therefore, synderesis will be directed to opposites, which is clearly false, because it always urges to good and never to evil.

2. If synderesis is a power, it is either the same as reason, or it is different from it. But it is not the same, because it is distinguished from reason in the comment of Jerome, as noted above. And we cannot say that it is different from reason, for a special power requires a special activity. And there is no act ascribed to synderesis which cannot be performed by reason. For reason itself urges to good and speaks out against evil. Therefore, synderesis is in no way a power.

3. The tendency to evil (fomes) always inclines to evil, and synderesis always to good. Therefore, these two are directly opposed. But the tendency to evil is a habit, or acts like habit, for concupiscence, which, according to Augustine, is habitual in children and actual in adults, is called the tendency to evil. Therefore, synderesis, also, is a habit.

4. If synderesis is a power, it is either cognitive or tends to action. But it is clear that it is not simply cognitive from the fact that its act is to incline us to good and warn us against evil. Therefore, if it is a power, it will tend to action. But this is obviously false, for the powers which tend to action are adequately divided into the irascible, the concupiscent, and the rational. And synderesis is distinguished from these, as has been said. Therefore, synderesis is in no way a power.

5. just as in the operative part of the soul synderesis never errs, so in the speculative part understanding of principles never errs. But understanding of principles is a habit, as is clear from the Philosopher. Therefore, synderesis is a habit.


There are various opinions on this question. For some say that synderesis designates simply a power, different from, and higher than, reason. Others say that it is, indeed, simply a power which is really identical with reason, but is considered as different from it. For reason is considered as reason, that is, in so far as it reasons and compares, and as such is called the reasoning power; it is also considered as a nature, that is, in so far as one knows something naturally, and thus it is called synderesis. Still others say that synderesis denotes the power of reason with a natural habit. We can see which of these is more true from what follows.

As Dionysius says, divine wisdom “joins the ends of nobler things with the beginnings of lesser things.” For natures which are ordained to one another are related to each other as contiguous bodies, the upper limit of the lower body being in contact with the lower limit of the higher one. Hence, at its highest point a lower nature attains to somet1iing which is proper to the higher nature and shares in it imperfectly.

Now, the nature of the human soul is lower than the angelic nature, if we consider the natural manner in which each knows. For the natural and proper manner of knowing for an angelic nature is to know truth without investigation or movement of reason. But it is proper to human nature to reach the knowledge of truth by investigating and moving from one thing to another.

Hence, the human soul, according to that which is highest in it, attains to that which is proper to angelic nature, so that it knows some things at once and without investigation, although it is lower than angels in this, that it can know the truth in these things only by receiving something from sense.

However, there is a double knowledge in the angelic nature: one, speculative, by which angels see the truth of things simply and independently; and the other, practical. This second type of knowledge is posited both by the philosophers, who hold that the angels are the movers of the heavens and that all natural forms pre-exist in their foreknowledge, and by the theologians, who hold that the angels serve God in spiritual duties, according to which the orders of angels are distinguished.

Hence it is that human nature, in so far as it comes in contact with the angelic nature, must both in speculative and practical matters know truth without investigation. And this knowledge must be the principle of all the knowledge which follows, whether speculative or practical, since principles must be more stable and certain. Therefore, this knowledge must be in man naturally, since it is a kind of seed plot containing in germ all the knowledge which follows, and since there pre-exist in all natures certain natural seeds of the activities and effects which follow. Furthermore, this knowledge must be habitual so that it will be ready for use when needed.

Thus, just as there is a natural habit of the human soul through which it knows principles of the speculative sciences, which we call understanding of principles, so, too, there is in the soul a natural habit of first principles of action, which are the universal principles of the natural law. This habit pertains to synderesis. This habit exists in no other power than reason, unless, perhaps, we make understanding a power distinct from reason. But we have shown the opposite above.

It remains, therefore, that the name synderesis designates a natural habit simply, one similar to the habit of principles, or it means some power of reason with such a habit. And whatever it is makes little difference, for it raises a doubt only about the meaning of the name. However, if the power of reason itself, in so far as it knows naturally, is called synderesis, it cannot be so considered apart from every habit, for natural knowledge belongs to reason by reason of a natural habit, as is clear of the understanding of principles.

Answers to Difficulties

1. Things can be parts of the same division in so far as both share in something common, whatever that common thing be, whether genus or accident. Accordingly, in the fourfold division in which synderesis is distinguished from the three powers, the members of the division are not distinguished from each other because all are powers, but because all are principles of action. Therefore, it does not follow that synderesis is a power, but that it is a principle of action.

2. Whenever something special, over and above that which belongs to a subject by its nature, is added to it by an accident, nothing prevents the accident from being distinguished from the subject, or the subject with the accident from being distinguished from the subject taken simply, as if I were to distinguish a colored surface from surface taken simply. For, in so far as surface is taken simply, it is something mathematical, but, if it is considered as colored, it is classified as part of physical reality. So, reason, also, designates knowledge on the human level, but knowledge through a natural habit is on a generically different level, as is clear from what has been said. Consequently, there is nothing to prevent the habit itself from being distinguished from the power in the division in which motive principles are distinguished, nor to prevent the power endowed with that habit from being distinguished from the power taken simply.

3. The other habits which inhere in the power of reason cause movement in the same way, according to the manner which is proper to reason as reason. Therefore, those habits cannot be distinguished from reason as is the natural habit from which synderesis takes its name.

4 We do not say that synderesis means a power and a habit, as though the power and the habit were one thing, but because the power together with the habit which it underlies is designated by one name.

5. That something is inscribed in another is understood in two ways. In one way, as in a subject, and in this sense something can be inscribed in a soul only with reference to a power. In another way, as in a container, and in this sense there is no reason why something cannot be inscribed even in a habit. It is in this sense that we say the single elements pertinent to geometry are inscribed in geometry itself.

6. This difficulty proceeds correctly when one thing results from two because of a mixture. But one thing does not thus result from a habit and a power which is like the union of an accident and its subject.

7.Sensuality always inclines to evil by reason of the corruption of the tendency to evil, and this corruption is in it after the manner of a habit. It is thus, too, that synderesis, by reason of a natural habit, always inclines to good.

8. White man cannot be defined with a strict definition, such as the definition of substances, which denotes something that is essentially one, but it can be defined by a definition in a loose sense, in so far as something that is loosely one results from an accident and its subject. This kind of unity is enough to give it one name. Hence, the Philosopher says” that a subject and its accident can be indicated by one name.

9. Synderesis does not denote higher or lower reason, but something that refers commonly to both. For in the very habit of the universal principles of law there are contained certain things which pertain to the eternal norms of conduct, such as, that God must be obeyed; and there are some that pertain to lower norms, such as, that we must live according to reason. However, synderesis is said to refer to these unchangeable things in one way, and higher reason in another. For something is called unchangeable because of an immutability of its nature, and it is thus that divine things are unchangeable. Higher reason is said to deal with unchangeable things in this way. A thing is also said to be unchangeable because of the necessity of a truth, although the truth may concern things which according to their nature can change. Thus the truth: every whole is greater than its part, is unchangeably true even in changeable things. Synderesis is said to refer to unchangeable things in this way.

10. Although everything, in the soul is only habit, or only power, or only passion, not everything which is given a name in the soul is one of these alone. For things which are distinct in reality can be joined and given one name by our understanding.

11. The innate habit which inclines to evil belongs to the lower part of the soul, by which it is joined to the body. But the habit which naturally inclines to good belongs to the higher part of the soul. Therefore, these two opposite habits do not belong to the same thing in the same way.

12. A habit together with a power is enough for the act of that habit. But the act of the natural habit called synderesis is to warn against evil and to incline to good. Therefore, men are naturally capable of this act. However, it does not follow from this that a man with purely natural gifts can perform a meritorious act. To impute this to natural capability alone is the Pelagian impiety.

13. In so far as synderesis means a power, it seems to indicate a passive rather than an active power. For an active power is not distinguished from a passive power because it has an activity, for since every power of the soul, active as well as passive, has some activity, every power would be active.

We learn the distinction between the two by comparing the power to its object. For, if the object relates to the power as that which undergoes and is changed, the power will be active. If, on the other hand, it relates as agent and mover, the power is passive. Hence it is that all the powers of the vegetative soul are active, because in nutrition, growth, and generation food is changed through the power of the soul. On the other hand, all the sensitive powers are passive, because they are set in motion and come into act through sensible objects. In our understanding, however, there is an active and a passive power, because through intellect the intelligible in potency becomes intelligible in act. This is the activity of the agent intellect, and our understanding is, thus, an active power. The thing actually intelligible also makes the understanding in potency understanding in act, and in this way the possible intellect is a passive power. The agent intellect, however, is not said to be the subject of habits. Rather, the possible intellect plays this role. Consequently, the power to which the natural habit is joined seems to be a passive rather than an active power.

But, granted that it is an active power, the reasoning is incorrect when it proceeds farther. For there are not two forms in the soul, but only one, which is its essence. For by its essence it is spirit, and by its essence it is the form of the body. It is not this by reason of anything else. As a result, higher and lower reason are not rooted in two forms, but in the one essence of the soul. Nor is it true that lower reason is rooted in the essence of the soul according to the relation by which it is the form of the body. For only the powers which are attached to organs are thus rooted in the essence of the soul, and lower reason does not belong to this class. Granted, too, that the power which synderesis denotes is the same thing as higher or lower reason, nothing prevents us from calling reason, the power simply, and synderesis, the same power with a habit inhering in it.

14. An act of knowing is not prerequisite for the power or habit of synderesis, but only for its act. Hence, this does not prevent the habit of synderesis from being innate.

15. Judgment is twofold: of universal [principles], which belongs to synderesis; and of particular activities, which is the judgment of choice and belongs to free choice. Consequently, it does not follow that they are the same.

16. Natural composition is manifold. One kind is the composition of a compound from elements. The Philosopher says19 that in this composition the form of the compound must be something entirely different from the elements. There is also the composition of a substantial form and matter, from which a third thing arises, the specific form, which is not altogether different from the matter and the form, but relates to them as a whole to its parts. There is also the composition of subject and accident, in which no third thing results from the two. The composition of a power and a habit is of this sort.


Q. 16: Synderesis


Secondly, we ask:

Can synderesis err [peccare]?

[Parallel readings: II Sent., 24, 3, 3; 39, 3, ; S.T., 1, 79, 12.]


It seems that it can, for

1. After discussing synderesis, Jerome remarks: “We sometimes see this fall down.” But, in matters of action, to fall down is nothing else than error. Therefore, synderesis can err.

2. Although error, properly speaking, belongs not to a habit or a power, but to the man, since acts belong to individuals, a habit or a power is said to err in so far as through the act of some habit or power a man is led into error. But a man is sometimes led into error through the act of synderesis. For in the Gospel of St. John (16:2) it is said: “Yea, the hour cometh, when whosoever killeth you, will think that he doth a service to God.” Thus, from the judgment that worship must be offered to God, which judgment certainly pertains to synderesis, some were disposed to kill the Apostles. Therefore, synderesis errs.

3. Jeremiah (2:16) says: “The children, also, of Memphis, and of Taphnes have deflowered thee, even to the crown of thy head.” But the crown is the higher part of the soul, as the Gloss on Psalms (7:17) says: “His iniquity shall come down on his crown. Thus, it belongs to synderesis, which is the highest thing in the soul. Therefore, synderesis is deflowered through sin by demons.

4. According to the Philosopher4 the power of reason is related to opposites. But synderesis is a power of reason. Therefore, it is related to opposites, and so can do good and commit sin.

5. Opposites are naturally produced in connection with the same thing. But virtue and sin arc opposed to each other. Since, therefore, the act of virtue is in synderesis, because it urges on to good, the act of sin will also be in it.

6. Synderesis takes the place in matters of action which the understanding of principles does in speculative matters. But all the activity of our reason arises from first principles. Therefore, all the activity of practical reason has its beginning from synderesis. Therefore, just as the activity of practical reason which is virtuous is ascribed to synderesis, so the activity of reason which is sinful is also attributed to it.

7. The punishment corresponds to the crime. But the whole soul of the damned, including syndousis, will be punished. Therefore, synderesis also sins.

To the Contrary

1. Good can be more pure than evil, for there is some good in which there is no admixture of evil, but there is nothing so bad that it does not have some admixture of good. But in us there is something which always inclines to evil, namely, the tendency to sin [fomes]. Therefore, there will be something which always inclines to good. But this seems to be only synderesis. Therefore, synderesis never sins.

2.What is naturally present is always present. But it is natural for synderesis to warn against evil. Therefore, it never consents to evil, and so never sins.


In all its activities nature intends what is good and the conservation of the things which are produced through the activity of nature. Therefore, in all the works of nature, the principles are always permanent and unchangeable and preservative of right order. For, as is said in the Physics: “Principles should be permanent.” For it would not be possible to have any stability or certainty in things which flow from principles if the principles themselves were not firmly established.

Consequently, all changeable things are reduced to some first unchangeable thing. Hence, too, it is that all speculative knowledge is derived from some most certain knowledge concerning which there can be no error. This is the knowledge of the first general principles, in reference to which everything else which is known is examined and by reason of which every truth is approved and every falsehood rejected. If any error could take place in these, there would be no certainty in the whole of the knowledge which follows.

As a result, for probity to be possible in human actions, there must be some permanent principle which has unwavering integrity, in reference to which all human works are examined, so that that permanent principle will resist all evil and assent to all good. This is synderesis, whose task it is to warn against evil and incline to good. Therefore, we agree that there can be no error in it.


Answers to Difficulties

1. Synderesis never falls down in a general principle, but error can happen in some application of a general principle to some particular case because of a false deduction, or because of a false assumption. Therefore, it does not say that synderesis simply falls headlong, but that conscience does, which applies the general judgment of synderesis to particular matters.

2.When in a syllogism one arrives at a false conclusion from two propositions, one of which is true and the other false, the mistaken conclusion is not attributed to the true, but to the false, proposition. Therefore, in that choice by which the murderers of the Apostles thought they were offering worship to God, the error did not come from the universal judgment of synderesis, that worship should be offered to God, but from the false judgment of higher reason, which considered the killing of the Apostles as pleasing to God. Therefore, we need not concede that they were inclined to sin through an act of synderesis.

3. As the crown of the body is the highest part of the body, so the crown of the soul is the highest part of the soul. Hence~ the crown of the soul is understood to mean different things according to the different distinctions of the parts of the soul. If we distinguish the intellectual part from the sensitive part, the whole intellective part of the soul can be called the crown. If we distinguish the intellective part further into higher and lower reason, higher reason is called the crown. If we distinguish reason further into natural judgment and deliberation of reason, natural judgment is called the crown. Therefore, when the soul is said to be deflowered even to its crown, crown isto be taken as denoting higher reason and not synderesis.

4. The power of reason, which of itself is related to opposites, is sometimes limited to one thing through a habit, especially if the habit is completely formed. Moreover, synderesis does ri~t mean the rational power simply, but as perfected by a completely determined habit.

5. The act of synderesis is not strictly an act of virtue, but a kind of prelude to the act of virtue, just as natural endowments are preludes to freely given and acquired virtues.

6. just as in speculative matters, although a mistaken reason starts from principles, it does not derive its falsity from first principles, but from wrong use of the principles, so the same thing also happens in practical matters. Therefore, the conclusion does not follow.

7. Augustine shows that this argument does not hold. For he says that “the whole man is damned” for the sin of lower reason alone, and this because both reasons belong to the “one person,” to whom sinning properly belongs. Therefore, the punishment looks directly to the person and not the power, except in so far as the power belongs to the person. For the person of man deserves punishment in all the parts of his person for a sin which he commits by one part of himself. Hence, also, in a civil trial the hand alone is not punished for the murder which a man commits with his hand.


Q. 16: Synderesis


In the third article we ask:

Are there some in whom synderesis is extinguished?

[Parallel readings: II Sent., 24, 2, 3, ad 5; 39, 3, 1.]


It seems that there are, for

1. On Psalms (5 2:2), “They are corrupted and become abominable,” the Gloss has: “Corrupted, that is, deprived of all light of reason.” But the light of synderesis is the light of reason. Therefore, in some men synderesis is extinguished.

2. Heretics sometimes have no remorse of conscience for their infidelity. But infidelity is a sin. Accordingly, since the function of synderesis is to protest against sin, it seems that it is extinguished in them.

3. According to the Philosopher, one who has a habit of vice loses the principles of action. But principles of action belong to synderesis. Therefore, in everyone who has the habit of some vice synderesis is extinguished.

4. Proverbs (18:3) says: “The wicked man when he is come into the depth of sins, contemneth.” When this happens, “synderesis does not hold its ground,” as Jerome says. Therefore, in some men it is extinguished.

5. Every inclination to evil is taken away from the blessed. Conversely, therefore, every inclination to good is taken away from the damned. But synderesis inclines to good. Therefore, it is extinguished in them.

To the Contrary

l. Isaiah (66:24) says: “Their worm shall not die.” According to Augustine this refers to the worm of conscience, which is remorse of conscience. But remorse of conscience is caused by synderesis protesting against evil. Therefore, synderesis is not destroyed.

2. Despair, which is a sin against the Holy Spirit, is in the lowest depths of sin. But, even in those who despair, “synderesis is not extinguished,” as is plain from Jerome, who says of synderesis: “Not even in Cain was it suppressed.” Nevertheless, it is clear that he despaired, for he said: “My iniquity is greater than that I may deserve pardon” (Genesis 4:13). We conclude as before.


That synderesis is extinguished can be undersiood in two ways. In one, it is considered in so far as it is an habitual light, and in this sensee it is impossible for synderesis to be extinguished, just as it is impossible for the soul of a man to be deprived of the light of the agent intellect, through which first principles in speculative and practical matters are made known to us. For this light belongs to the nature of the soul, since by reason of ‘this the soul is intellectual. In Psalms (4:7) it is said of this: “The light of thy countenance, O Lord, is signed upon us,” so that it shows good things to us. For this was the answer to the question: “Many say: Who sheweth us good things?” (Psalms 4:6).

In the other way, in so far as it is an act, it can be extinguished in two ways. In one, the act of synderesis is said to be extinguished inasmuch as it is completely interfered with. This happens in those who do not have the use of free choice or of reason because of an impediment due to an injury to the bodily organs from which our reason needs help. In the other way, the act of synderesis is deflected toward the contrary of synderesis. It is impossible for the universal judgment of synderesis to be destroyed in this way, but in a particular activity it is destroyed whenever one sins in choice. For the force of concupiscence, or of another passion, so absorbs reason that in choice the universal judgment of synderesis is not applied to the particular act. But this does not destroy synderesis altogether, but only in some respect, Hence, absolutely speaking, we concede that synderesis is never destroyed.

Answers to Difficulties

1. Some sinners are said to be deprived of all light of reason in the act of choice, in which reason errs because it is engrossed by some passion, or oppressed by some habit so that it does not follow the light of synderesis in making its choice.

2. In heretics their conscience does not reprove their infidelity by reason of the error in their4figher reason, because of which the judgment of synderesis is not applied to this particular case. For the universal judgment of synderesis remains in them, since they judge it to be evil not to believe what God has said. But they err in higher reason, because they do not believe that God has said this.

3 One who has the habit of some vice does indeed lose the principles of activity, not as universal principles, but in their application to some particular case, in so far as through some vicious habit his reason is stifled in order to keep it from applying the universal judgment to its particular activity when making its choice. In this way, also, the wicked man who falls into the depths of sin is said to have contempt.

4. The solution to the fourth difficulty is clear from the answer to the third.

5. Evil is not part of a nature; therefore, there is nothing to prevent the removal of the inclination to evil from the blessed. But good and the inclination thereto result from the nature itself; hence, as long as the nature remains, the inclination to good cannot be taken even from the damned.