Commentaria in Summam contra Gentiles, Liber III

Having seen in general that man is ordered according to reason by divine law concerning bodily and sensible things, we must see in particular how he is ordered concerning the use of venereal things and food, regarding which man is most affected¹. And first we must see concerning the use of venereal things; second, concerning the use of food, ch. 127.

As to the first, St. Thomas does two things: first, he shows that according to divine law fornication is a sin, and marriage is natural; second, he explains the conditions of marriage, in the following chapters.

As to the first, he does three things: first, he proposes the argument of certain people who say that fornication is not a sin; second, he determines the truth ²; third, he excludes a certain objection ³.

I. First, therefore, he says that some argue that fornication is not a sin, because, if someone approaches a woman who is free from a husband and existing under the power of no one, with her consent, he neither does an injury to her, because it pleases her and she has power over her own body; nor to another, because she is posited to be under the power of no one. Therefore it is not a sin.

Nor is it enough to say that he does an injury to God. Because God is not offended by us except by the fact that we act against our own good. But this does not appear to be against man's good.

Nor is it enough, either, to say that an injury is done to the neighbor, who is scandalized by this. Because it happens that someone is scandalized by something which is not a sin in itself, and thus it is a sin per accidens: but we are now dealing with whether fornication is a sin per se.

II. Second, he determines the truth ⁴. And he posits two conclusions ⁵. The first is: Fornicatory intercourse is a sin. And this is understood per se: and not merely because it is prohibited.

It is proved. Every emission of semen in accordance with which generation cannot follow per se, or, if generation can follow, the proper upbringing of the offspring is impeded, is against man's good. And if it is done on purpose, it must be a sin. But it happens thus in fornicatory intercourse. Therefore etc.

The major premise is proved. The good of each thing is that it attain its end: but evil is that it turn aside from its due end. And this ought to be considered in the parts just as in the whole. But semen is necessary for the propagation of the species: whereas other superfluous matters are necessary for nothing, such as excrement, urine, sweat, and the like. Therefore it belongs to the good of man that it be emitted for the utility of generation: and also that the proper upbringing of the one begotten can follow, because the one begotten would not survive if due nutrition were withheld. Therefore etc.

The minor, in turn, is proved: namely, that by fornicatory intercourse the proper upbringing of the one begotten is impeded. It is fitting according to human nature, namely for the upbringing of offspring, that a man remain together with the woman after intercourse, and not depart immediately, approaching any woman whatever indifferently. Because the female would by no means suffice alone for the upbringing of the offspring: since the necessity of human life requires many things that cannot be provided by one alone. Now we see in animals in which the female does not suffice for the upbringing of offspring that the male and female remain together after intercourse, so long as is necessary for the upbringing and instruction of the offspring. But the fornicator does not remain together with the female, but departs immediately, approaching any woman whatever indifferently. Therefore etc.

Nor does it stand in the way of this proof that a certain woman is capable through her wealth of nourishing the offspring alone. Because natural rectitude in human acts is not according to those things that happen per accidens in one individual, but according to those things that follow the whole species.

2. For the clarity of this argument, it should be considered that it belongs to the fornicatory act per se that the man is not bound to remain together with the female after intercourse: since through it he is restricted to this by no bond, insofar as he is a fornicator; and as far as pertains to the very nature of the fornicatory act, one is not prohibited from approaching any other woman whatever. Therefore, as far as pertains to itself, it is impeditive of the proper upbringing of the offspring, which does not take place properly unless the male remains together with the female after intercourse. And consequently it is per se against the good of man, and is a sin.

Hence, although some fornicator may remain together with the woman for a long time after intercourse and assist in the upbringing of the offspring, this does not take away from the fornicatory act being a sin: because it is per accidens that this man remains together with the woman. But per se it does not belong to that act that the fornicator have to remain together with the female: because no obligation of his to this has been made. And because, as is said here, rectitude or deviation from reason in human acts is considered according to that which belongs to them per se, but not according to that which belongs to them per accidens; therefore it must be said absolutely that every fornicatory act is an evil for man, as being impeditive of the end to which the emission of semen is ordered per se and by its nature, and is a sin, notwithstanding those things that sometimes accompany this act in some man per accidens.

The argument of St. Thomas, therefore, proceeds from propositions that are formally and per se true, from which arguments have efficacy, although per accidens they sometimes seem to be false. Hence that proposition which he assumes, namely, The fornicator departs immediately, approaching any woman whatever indifferently, is true speaking per se of a fornicator, and with respect to that which belongs to a fornicator insofar as he is a fornicator: although in some fornicator it can be false per accidens, namely by reason of something joined to the fornication, by which the fornicator is induced to remain together with the female after intercourse.

III. The second conclusion is ⁶: Marriage is natural to man. Understand this, as is said in IV Sent., d. 26, q. 1, a. 1, not because it follows from the necessity of nature, but because there is a natural inclination toward it, which is completed through the mediation of free choice.

It is proved. It is natural to man that a man have not an association for a short time, but a lasting association with a determinate woman. Therefore marriage is natural to man.

The consequence is proved. Because we call this association marriage. — But the antecedent is proved. It is necessary that the male remain together with the female in all animals so long as the work of the father is necessary for the offspring. But in man the work of the father is necessary for the offspring through a great space of life. Because children need instruction with respect to the soul, of which they are not capable except after a long time, and especially when they reach the years of discretion, and for which a long time is required: they also need repression on account of the impulses of the passions, by which the judgment of prudence is corrupted. But for this the woman alone does not suffice, but rather the work of the father is required, in whom there is both more perfect reason for instructing and more powerful strength for chastising. Therefore etc.

2. It should be noted that St. Thomas, intending to conclude that marriage is natural to man, assumed that it is necessary that the male remain together with the female so long as the work of the father is necessary for the offspring. On account of which it could seem to someone that he did not argue well. But if it is carefully examined, the argument proceeds exceedingly well. For St. Thomas does not make a difference in this place between necessary and natural: because it is sufficiently evident that what is necessary in all animals is according to the inclination of nature; hence to say that something is necessary for all animals, and that it is natural, can suitably be taken for the same thing. But St. Thomas, aiming at brevity, used the name of necessary in that proposition rather than the name of natural, because the final cause why a natural inclination to something has been given to anything is because that thing is necessary for it. Therefore, while something is said to be necessary for animals, both its naturalness is said implicitly, and the cause of its naturalness is explained.

3. Concerning that proposition, We call the lasting association of a man with a woman marriage, it should be noted that marriage can be taken in two ways for the present: in one way, as it is for an office of nature, namely as ordered to the generation and upbringing of offspring, which is principal in marriage; in another way, as it is a sacrament of the Church. St. Thomas's proposition, therefore, is to be understood of marriage taken in the first way, which is common to every state of men. For in this way marriage is nothing other than the obligation of a man to remain together with a determinate woman, on account of the generation and upbringing of offspring. But marriage taken in the second way adds above this the character of being a sign of the conjunction of Christ and the Church ⁷.

IV. Third, St. Thomas removes a certain objection against the first conclusion ⁸. For someone could deem, from the argument adduced, that it is a slight sin if someone procures the emission of semen outside the due end of generation and upbringing. Because it is either a slight sin, or no sin at all, if someone uses some part of his body for another use outside that to which it is ordered according to nature: as if someone should walk on his hands, or perform with his feet something to be performed with his hands.

Now he answers that it is not similar concerning these inordinate uses and concerning the inordinate emission of semen. Because through those man's good is not much impeded: but this is repugnant to the good of nature, which is the preservation of the species. — From which it is inferred that this kind of sin seems to hold the second place after the sin of homicide.

2. From that answer, it must be observed that it is not to be taken as the total reason why fornication, or any emission of semen from which generation of offspring or its proper upbringing cannot follow, is a sin, that whenever the use of some part of the body is not according to the order of nature, then it is a sin: for it is evident that this is not universally true in the use of hands and feet. But it is necessary to add that such inordinate use be such that an evil of nature follows from it: because, namely, either the good of nature is totally taken away through it, or it is impeded. For then, because the emission of semen from which offspring either cannot be generated or cannot be properly brought up is against the good of the offspring to be generated, and thus is against the good of nature, which is preserved by the generation of offspring and upbringing, it can be argued that it is a sin per se. For this reason St. Thomas, in IIa IIae, q. 154, a. 2 and 3, shows that fornication is a mortal sin by no other reason than because it imports an inordination which tends to the harm of the life of him who is to be born from such intercourse. For what is committed directly against the life of man is a mortal sin.

V. But it does not seem that the doubt is satisfied by this answer, on account of two things. First, because St. Thomas, at the beginning of his determination, assumes this proposition, that the good of each thing, both in the whole and in the parts, is that it attain its end, but evil is that it turn aside from the due end. But if someone uses a part of the body for other than what it is ordered to, the part is turned aside from the due end. Therefore it is done against man's good if someone uses some part for another use than for that to which it is ordered, just as if semen is emitted in a manner by which generation or upbringing of offspring cannot follow: for in both ways man's end is impeded with respect to a part. Therefore the one will be a sin just as the other.

Second, if such an emission of semen is a sin because it is against the good of the offspring to be procreated and against the preservation of the species, it follows that no one will be able to preserve continence without sin: because the preservation of the species is also impeded through continence, as far as is on the part of the continent man.

2. To the first of these it can be answered in two ways. First, that indeed, while someone uses any part whatever for another use than was instituted by nature, it is done in some way against man's good, insofar as it is turned aside from the due end: nevertheless it is not done against a great good of man, so that it would be a sin. But in the inordinate emission of semen it is done against a great good of man: because it is done against the upbringing of the man to be born, and against the preservation of the species. Therefore it is not similar concerning other inordinate uses and concerning the inordinate emission of semen. Now this seems to be of the mind of St. Thomas in the aforesaid answer: because he does not make a difference between these as if in those it is in no way done against man's good, while in this it is done; but because through those man's good is not much impeded, while through this it is much impeded.

It can be answered, second, that it is not an evil for man that someone, having omitted the operation and use of a part intended by nature, use the part for another use: because reason can use every part of the body as an instrument even for another use than it was instituted for by nature. But it is certainly an evil for man if the natural operation, and the proper use of the part, is performed in such a way that it is not fitting for the end which nature intends through such use and operation, but rather is contrary to it: as happens in the inordinate emission of semen. Hence what St. Thomas says, that it is the evil of each thing that it turn aside from the due end, is to be understood, not through the cessation of its proper operation and use, where the thing is not instituted for some continuous operation: but through the unfittingness and disproportion of the proper operation and proper use to the end intended by nature.

3. To the second, it is said that one must speak in one way of him who ceases from the propagation of the species through cessation from the work ordered to the propagation of the species: and in another way of him who performs the operation ordered to the propagation of the species in a manner by which such propagation cannot follow. Because the former does not produce an act deprived of due order, nor does he act against the good of nature, since such propagation is sufficiently fulfilled through others: but the latter certainly acts against the good of nature, and does injury to it, because he deprives the action that he performs of its due end to the prejudice of the offspring that could be born from it, or that is to be born. For, as is had from the teaching of St. Thomas, IIa IIae, q. 152, a. 2 ⁹; and IV Sent., d. 26 ¹⁰, a. 2, to that to which nature inclines as necessary for the perfection of the multitude, not every man is bound by way of a precept, where it is satisfied through others, otherwise everyone would be bound to agriculture, which is necessary for the community: but it suffices that some of the multitude carry it out. But where someone exercises an operation of nature, he is bound to exercise it in such a way that the end of nature is not impeded, as far as is from the very manner of acting per se.

4. Concerning that which St. Thomas infers from the answer ¹¹, it should be noted that, since the inordinate emission of semen is a sin because it is an act inordinate per se, and is against the good of the human species, its gravity, among other sins by which it is acted against the good of man, is to be considered according to the evil that follows from it to the human species. Now the evil that is done to the human species through it, as is said here, is the impediment of the generation or upbringing of the offspring to be born, which does not yet participate in the species in actu. But the evil that is done through homicide is the deprivation of the upbringing and life of a man already born, and participating in the species in actu. Because, therefore, harm in the life and upbringing of a man already born and participating in the species in actu is a greater evil of human nature than of a man to be born and having the species only in potency, as one who can be impeded from many causes; and this is a greater evil than harm in exterior things: therefore it was fittingly said that, after the sin of homicide, this kind of sin holds the second place, namely among the sins that are against the good of man.

VI. The first conclusion ¹² is confirmed by divine authority: Lev. 18, indeed, and 1 Cor. 6, as to this, that every emission of semen from which offspring cannot follow is illicit; Deut. 23, in turn, and Tob. 4, and 1 Cor. 6, as to this, that fornication, and all intercourse other than with one's own wife, is illicit.

Now through this is excluded the error of those who say that in the emission of semen there is no greater sin than in the emission of other superfluities; and of those who say that fornication is not a sin.

Now it should be noted that St. Thomas from what has been said leaves the argument of the adversaries resolved ¹³. For it is evident that that consequence is not valid: No injury is done in fornication to the woman, nor to any other man in whose power she is. Therefore it is not a sin. For an act inordinate of itself is done, and it is done against the good of man, as has been shown: and therefore it is a sin.

It should also be noted that through that proposition posited at the beginning of the determination ¹⁴, namely, God has care of each thing according to that which is good for it, St. Thomas wishes to infer that fornication, and every inordinate emission of semen, is fittingly prohibited by divine law. For since God governs each thing by ordering it to that which is good for it, and consequently by removing what is evil for it; and it is good for man that he procure every emission of semen in such a way that it is fitting for the generation and upbringing of offspring: it belongs to the divine law, according to which man is governed, that it prohibit an emission of semen disproportionate to that end.

Against St. Thomas's argument by which he proves that fornication is a sin, it is urged by some in many ways.

But their arguments proceed from those things that can be found in the fornicatory act per accidens. But St. Thomas's argument is founded upon that which belongs to fornication per se, from which the character of sin must be taken. Therefore they do not weaken St. Thomas's argument. But because the Reverend Cardinal Cajetan, in IIª IIae, q. 154, a. 2, resolves them individually in a most sufficient manner, we need not now labor in resolving them.