Summa Theologiae Moralis, vol. I: De Principiis

S. Th. I, q. 79, a. 13; Q. D. de Verit. 17, a. 1, 2, 3; II Sent. d. 24, q. 2, a. 4.

199. Notions. — Conscience (συνείδησις), from the word conscire, i. e. to know together, etymologically is, as it were, knowledge with another, and therefore sometimes signifies knowledge had with others, that is, the common knowledge of several (Cicero, or. 1 in Catil., 1; Tacitus, Agr. 2); but more commonly it signifies the knowledge of one kept by himself but considered in relation to something else and applied to it, whence properly it imports the order of a piece of knowledge to something, and is the act by which we apply knowledge to a particular deed. This can be done in two ways:

1° by applying the piece of knowledge to consider that something is or was, and this is conscience merely psychological, by which we know that we are doing something, or recognize that we have done or not done something: this is said to testify and includes an intimate sense and memory (Gen. XLIII, 22; Rom. IX, 1; Eccl. VII, 23; II Cor. IV, 2; V, 11);

2° it can also be done by applying knowledge to consider whether something is rightly being done or has been done or not, and this is moral conscience, which is a judgment about good and bad acts and the application of moral knowledge to our human works. This again is twofold: for moral knowledge can be applied

a) to examine something that has been done and to judge whether it was well done or not, and this is consequent conscience, which is said to excuse, or to accuse or to gnaw (Hebr. IX, 14; Rom. II, 15; Tit. I, 15; II Tim.

I, 3; II Cor. I, 12; Is. LXVI, 24 and Mk. IX, 40: the worm of conscience, namely, does not die);

b) to direct something that can still be done, and to judge it to be good and to be done, or bad and not to be done, and this is antecedent conscience, which is said to urge, induce, bind, press, or hinder (Rom. XIII, 5). This is a judgment about the morality of an act to be placed here and now in the individual case and the application of moral knowledge to a determinate act. And it is moral conscience in the strict sense, because it alone is the rule of human acts, and of it we speak in the present treatise.

Improperly conscience is taken, either a) for its object (or the thing stirred up), i.e. for what is in our conscience (I Tim. I, 5), as when someone says: I shall tell you my conscience; to examine the conscience, or to be defiled or cleansed of it; or b) for its cause: then for the habit by which we are rendered capable of judging good and evil¹, and for the habitual disposition by which we are inclined to judge in this or that way about the honesty of an action; then for the knowledge of the law or the universal judgment about the morality of acts in general, without applying it to a determinate act, and so we say a seven-year-old child has a conscience of good and evil.

200. Antecedent conscience is a judgment, but not every antecedent judgment is conscience. For there is

1. a judgment merely speculative and of the truth of the thing alone, without respect to operation, e. g. whether Peter has money;

2. a speculative-practical judgment (i. e. speculative about practice) about the morality of our acts in general and in the abstract, insofar as they are considered in themselves and without order to the subject acting here and now. E. g. it is a judgment about objective and material honesty, which is twofold: for man

a) either makes wholly universal moral judgments to which he assents by the first practical principles, e. g. Good is to be done, evil is to be avoided; injury is to be done to no one; what you do not wish done to you, do not do to another; the Supreme Good is to be loved, etc., in which the intellect does not err, because it naturally possesses for perceiving and enunciating them a (readier) habit which is called synderesis;

b) or makes less universal judgments, to which he assents by general conclusions deduced immediately or mediately from the first principles, e. g. theft is to be avoided, fornication is illicit, etc., in which the intellect can sometimes err, but for which it can nevertheless acquire a habit which is called moral science;

3. a practico-practical judgment about the morality of the act in particular and in the concrete to be placed here and now by the acting subject, by which we apply the first universal principles or moral science to the particular case in particular conclusions, e. g. now to take this sum from Peter, unknown to him and without reason, is theft to be avoided. This is the particular judgment of conscience which is immediately ordered to operation and deals with subjective and formal honesty, and is proximately practical in relation to the universal judgments of synderesis and moral science, which are remotely practical; hence by some it is called the ultimately practical judgment, not simply, namely, but among those three that are about honesty;

4. an ultimately-practical (or discretive of election) judgment, not about morality but about the fitness of the act, namely about what is here and now to be chosen and ought to be done, whether it be good or bad: this follows conscience, by which it ought to be directed, but is often contrary to it, e. g. I shall seize Peter's money, although conscience says it is forbidden.

201. Conscience is defined as: the dictate or judgment of the practical intellect affirming an act in particular to be licit or illicit, and therefore to be placed (or capable of being placed) or to be omitted by us. In which definition is indicated

1° the genus to which conscience belongs, namely dictate or judgment, and so it is distinguished from reason, which is a power, from synderesis, which is the habit of the first practical principles by which we are capable of having conscience, from moral science, which is the habitual acquired knowledge of the morality of acts in general, from prudence, which is the virtue inclining to rightly estimating all the circumstances of the concrete act, and to rightly judging of its morality, or to having a right conscience, and to commanding what it says: for conscience is not a habit but an act, and therefore is easily reformed and laid down; if it is said to persist, this is not to be understood as persisting in itself, but in its causes, which are reason and synderesis, or also the others mentioned above;

2° the subject in which it resides: a) the intellect: for the judgment is not in the will but precedes it, that it may will good and flee evil; if conscience is called good or bad, it is not such formally in itself (as if it were the subject of goodness), but regulatively and from its effect, insofar as it directs good or bad works;

b) the practical: for it does not stop in the contemplation of truth but directs to the execution of the work, and so it is distinguished from judgments merely speculative and from psychological conscience;

3° the specific object: a) affirming an act in particular, i.e. in the concrete with its end and circumstances considered, as it can here and now be placed, and so it is distinguished from the speculative-practical judgments of moral science;

b) to be licit or illicit, and so it differs from other practical judgments which deal with usefulness, fitness, facility, etc., among others from the ultimately-practical judgment;

c) and therefore here and now to be placed or omitted: for it judges about an act to be placed, not about an act already placed, and so it is distinguished from consequent conscience;

d) by us: for conscience regards only one's own acts and not those of others (Rom. XIV, 4; I Cor. IV, 4, 5).

202. Conscience is the conclusion of a practical syllogism; whose Major is from synderesis, e. g. evil is to be fled², — the minor from reason: now to have intercourse with such a married woman is an evil; — conscience draws the conclusion: therefore to me here and now that intercourse with her is illicit.

But just as in speculative syllogisms there can be a false conclusion, so also in conscience, either a) on the part of the form, because it is badly deduced from true principles that are not rightly applied, e. g. God is to be obeyed; but God commands that the needy be helped; therefore I ought here and now to help such a neighbor; — or b) on the part of the matter, because it is deduced from a false principle, e. g. What is not forbidden is not evil; but intercourse with such an unmarried woman is not forbidden; therefore it is not evil. For although in the Major falsity cannot occur, because synderesis does not err about the first principles, reason can nevertheless err in the minor about particular principles³.

203. Principle. Conscience is the proximate and subjective rule of human acts, binding not by itself and by its own force, but by the force of the divine precept, because it applies the objective and remote rule or law to the particular case in order to the operation of the subject. As if the command of the emperor did not reach the citizens except through a legate, the command of the legate would not bind except because it promulgates the imperial command (q. 19, a. 5, ad 2; II Sent. d. 39, q. 3, a. 3, ad 3). Hence conscience is intimately and, as it were, the promulgation of the law with regard to the act to be placed here and now.

«Conscience, says S. Bonaventure, II Sent. d. 39, a. 1, q. 3, is like the herald and messenger of God; and what it says, it does not command from itself, but commands as from God, like a herald when he publishes the edict of the king; and hence it is that conscience has the power of binding». — Another comparison is used by S. Thomas, Q. D. de Ver. 17, a. 3, namely of a physical bond by which we are bound only through contact or application to a body, whence the moral bond or law binds only through the application of the law which is made through the knowledge of the precept and conscience: «Thus the command of one who governs stands in relation to binding in voluntary matters in that mode of binding which can accrue to the will (namely, by a necessity of moral obligation), as bodily action stands in relation to binding bodily things by a necessity of coercion. Now bodily action of an agent never induces necessity in another thing except through the contact of its coercion with the thing on which it acts. Hence neither by the command of any king or lord is anyone bound, unless the command reaches him to whom it is commanded. But it reaches him through knowledge. Hence no one is bound by any precept except through the knowledge of that precept... Just as in bodily matters a bodily agent does not act except through contact, so in spiritual matters a precept does not bind except through knowledge. And therefore, just as it is the same force by which touch acts and by which the power of the agent acts, since touch does not act except from the power of the agent, and the power of the agent not except through touch; so the same force is that by which the precept binds and that by which conscience binds, since the precept does not bind except by the force of knowledge nor knowledge except by the force of the precept. Hence, since conscience is nothing other than the application of knowledge to an act, it is evident that conscience is said to bind by the force of the divine precept».

From this it follows that conscience binds more than the precept of a human superior: «Conscience does not bind except by the force of the divine precept... Hence, since the divine precept binds against the precept of a prelate, and binds more than the precept of a prelate, conscience will be a bond greater than the bond of the precept of a prelate, and conscience will bind, the precept of a prelate being to the contrary» (ibid. a. 5).

But just as law, so conscience, by reason of the mode by which it binds, namely of obligation, is binding (or prescribing), whether negatively forbidding or positively commanding; and not binding (or not prescribing), which is permitting and counseling.

204. Remark. — Only antecedent conscience, because it alone influences the act, is its rule, but not consequent conscience, which supposes the act; hence beginners, who think otherwise, must be told that the goodness or malice of a past act is to be judged, not according to the knowledge they now have, but according to that which they had before the act.