D. 40 - On consanguinity

After the Master has considered the impediment by which a person is made legally incapable of marriage with some other person because of distance between them, here he begins to determine the impediments by which a person is rendered legally incapable of marriage with another person because of close relationship between them; and this is divided into two parts: in the first part he considers the impediment of a physically close relationship; in the second part, the impediment of a spiritually close relationship, in Distinction 42, where he says: let us now add something concerning spiritual relationship. (Sententiae IV, 42.1 (237). 1.)

The first is in two parts: in the first he considers consanguinity; in the second, affinity, Distinction 41, where he says, now we must examine affinity. (Sent. IV, 41.1 (228). 1.)

The first is in two parts: in the first he shows which degrees of consanguinity impede marriage; in the second he objects to the contrary, and resolves it, where he says, with these statements contrasts that which “Gregory replies to Augustine, bishop of the English . . .” (Sent. IV, 40.4 (227). 1, uncertain source; cf. Hugh of Saint Victor, De sacramentis, bk 2 pt. 11 c14.)

The first is in two parts; in the first he shows in what degrees consanguinity impedes marriage; in the second he shows the reason for this distinction, where he says, Isidore explains why he counts six degrees. (Sent. IV, 40.3 (226). 1.)

The first is in two parts: in the first he shows which degrees of consanguinity impede marriage; in the second he shows how these degrees are calculated, where he says, as to how the degrees of consanguinity are to be computed, Isidore shows this as follows. (Sent. IV, 40.2 (225). 1.)

Question 1

On consanguinity

Here four questions arise:

first, what consanguinity is;

• second, how it is distinguished;
• third, whether in some degrees it impedes marriage by natural law;
• fourth, whether the degrees that impede marriage can be determined by the statutes of the Church.
• Article 1

What consanguinity is

Obj. 1: To the first question, we proceed thus. It seems that the definition of consanguinity that certain people put forth is inadequate, namely: consanguinity is the bond contracted between those descended from a common root by carnal propagation. (Raymond of Peñafort, Summa, Bk. 4, tit. 6, sec. 1 (487b); Albert the Great, In IV Sent., d. 40, a. 1 (BO 30:443); John of Andrew, Declaratio arboris consanguinitatis, sec. 6 (RF I:1427).) For all men are descended by physical propagation from the same root, namely from Adam. Therefore, if the definition above were right, all men would be consanguineous with each other, which is false.

Obj. 2: Furthermore, a bond can only exist between two things that fit together, for a bond unites. But those who are descended from one root do not fit with each other more than with other people, since they are identical in species, and differ in number, just like any other people. Therefore, consanguinity is not a particular bond.

Obj. 3: Furthermore, carnal propagation, according to the Philosopher, (Aristotle, Generation of Animals, Bk. 1, ch. 18 (726a26).) occurs from an excess of food. But such an excess has more to do with things eaten, with which it agrees in substance, than with the one who eats. Therefore, since no bond of consanguinity arises between the one born of semen and the things he eats, neither does any bond of close relationship to the one generating arise by physical propagation.

Obj. 4: Furthermore, in Genesis 19:14, (In fact, Genesis 29:14.) Laban said to Jacob, you are my bone and my flesh, by reason of the family relation between them. Therefore, a close relationship like this should be called fleshliness rather than consanguinity.

Obj. 5: Furthermore, physical propagation is common to men and animals. But among animals no bond of consanguinity is contracted in physical propagation. Therefore, neither does it happen in men.

I answer that, according to the Philosopher in the Ethics 8*, all friendship consists in some kind of sharing*, (Aristotle, Nicomachean Ethics, Bk. 8, ch. 12 (1161b11).) and since friendship is a certain tie or union, the sharing that is the cause of the friendship is called a bond. And for this reason, some people are named by whatever they share as though they were tied to each other, like those are called ‘compatriots’ who share with each other a political community, and ‘comrades-in-arms’ who share in military pursuits. And in the same way, those who share something in common at the level of nature are called ‘consanguineous’. And so in the definition above, the genus of consanguinity is given as bond; as its subject, persons descending from one root, who have this kind of bond, of which the principle is carnal propagation.

Reply Obj. 1: The active force is not found according to the same perfection in the instrument as it is in the principal agent. And since every moved thing that moves is an instrument, it is for this reason that the strength of the first mover in any genus runs out in the end, diffused through the many intermediaries, and ends in something that is only moved, not a mover. But the power of the one generating moves not only what has to do with the species, but also what has to do with the individual, for which reason a son resembles his father not only in the nature of the species, but even in accidental things. But nevertheless the character of the father is never so completely in the son as it was in the father, and in the grandson even less, and it is weakened from that point on. And so it is that that character sometimes runs out, so that it cannot proceed any further. And since consanguinity exists inasmuch as many share in such a character diffused from one throughout many by propagation, over time consanguinity dissolves, as Isidore says; (Isidore, Etymologies (OCT, ed. Lindsay), Bk. 9, ch. 6, par. 29.) and so it is not necessary to include the remote root in the definition of consanguinity, but the near one, whose strength still remains in those who are propagated by it.

Reply Obj. 2: From what has been said it is already clear that the consanguineous do not only share in the nature of the species, but also in the proper virtue of the individual himself, passed on from one to many, by which it sometimes happens that a son not only resembles his father, but also his grandfather, or remote forebears, as is said in Book 4 of On the Generation of Animals. (Aristotle, Generation of Animals, Bk. 4, ch. 3 (768a24).)

Reply Obj. 3: Agreement between things is more attendant on form, according to which something is in act, than upon matter, according to which something is in potency; which is clear in the fact that charcoal has more in common with fire than with the tree from which the wood was cut. And likewise, food, which has already been transformed into the species of the one nourished by the nutritive power, has more to do with the nourished person himself than with that thing from which nourishment was taken. However, the argument might proceed according to the opinion of those who said that the entire nature of a thing is its matter, and that all forms are accidents; which is false.

Reply Obj. 4: What is most immediately converted into semen is blood, as is proved in Book 1 of On the Generation of Animals. (Aristotle, Generation of Animals, Bk. 1, ch. 19 (726b9).) And because of this, the bond that is contracted by propagation of the flesh is more fittingly called consanguinity than fleshliness. And when someone consanguineous is said to be the “flesh” of another, this is because blood, which is converted into semen in a man or into the menstrual flow, is flesh or bone potentially.

Reply Obj. 5: Certain people say that the bond of consanguinity is contracted among people by physical propagation, and not among other animals, because whatever belongs to the truth of human nature in all people existed in our first parents, and did not exist in other animals. But according to this, consanguinity would never be dissolved.

But this position was disproved in the corpus of Book II, Distinction 30, Question 1, Article 2; therefore it must be said that this is fitting, for animals are not joined together into the unity of friendship on account of the propagation of many from one close forebear, as is the case with humans, as was said in the body of this article.

Article 2

How it is distinguished

Obj. 1: To the second question, we proceed thus. It seems that consanguinity is not suitably distinguished into lines and degrees. For the line of consanguinity is said to be the ordered series, containing diverse degrees, of persons related by blood, having descended from the same root. (Raymond of Peñafort, Summa, Bk. 4, tit. 6, sec. 1 (487b); Albert the Great, In IV Sent., d. 40, a. 3 (BO 30:445); John of Andrew, Declaratio arboris consanguinitatis, sec. 7 (RF I:1428).) But consanguinity is nothing other than the series of such persons. Therefore, the line of consanguinity is the same as consanguinity. But nothing should be distinguished by itself. Therefore, consanguinity is not fittingly distinguished by lines.

Obj. 2: Furthermore, what some common thing is divided by cannot be included in the definition of the common thing. But descent is included in the definition given above for consanguinity. Therefore, consanguinity cannot be divided by lines of ascending and descending and collaterals.

Obj. 3: Furthermore, the definition of a line is that which is between two points. (See Euclid, Geometry, as interpreted by Boethius, Bk. 1 (PL 63:1307).) But two points only make one degree. Therefore, one line has only one degree; and so the division of consanguinity by lines and by degrees seems the same.

Obj. 4: Furthermore, degree is defined as the relationship of distant persons by which it is known by how much distance the persons are separated from each other. (Raymond of Peñafort, Summa, Bk. 4, tit. 6, sec. 2 (489b); Albert the Great, In IV Sent., d. 40, a. 5 (BO 30:446); John of Andrew, Declaratio arboris consanguinitatis, sec. 8 (RF I:1428).) But since consanguinity is a certain close relationship, distance between persons is more opposed to consanguinity than it is a part of it. Therefore, consanguinity cannot be distinguished by degrees.

Obj. 5: Furthermore, if consanguinity is distinguished and known by degrees, it is necessary that those persons who are in the same degree are equally consanguineous. But this is false; for a great-uncle and his great-nephew are in the same degree, but they are not equally consanguineous, as the decree states. (See Arbor consanguinitatis (RF I, 1425–26), and John of Andrew’s Declaratio (RF I, 1427).) Therefore, consanguinity is not rightly distinguished by degrees.

Obj. 6: Furthermore, in ordered things, anything added to another makes another degree; just as any added unit makes another species of number. But a person added to a person does not always make another degree of consanguinity: for a father and a paternal uncle who is related to him are in the same degree of consanguinity. Therefore, consanguinity is not correctly distinguished by degrees.

Obj. 7: Furthermore, between two relatives, there is always the same closeness of consanguinity: for one of two extremes is equally distant from the other and vice versa. But the degree of consanguinity is not always found to be the same on both sides, since sometimes one relative is in the third degree and the other is in the fourth. Therefore, the closeness of consanguinity cannot sufficiently be known by degrees.

I answer that, consanguinity, as was said, is a certain close relationship, founded on a sharing at the natural level resulting from the act of generation, by which nature is propagated. Therefore, according to the Philosopher in the Ethics 8, this sharing can happen in three ways. (Aristotle, Nicomachean Ethics, Bk. 8, ch. 12 (1161b11).) One is according to the relation of the principle to what depends on it, and this is the consanguinity of the father to the son; and thus he says that parents love their children as being some part of their own selves. (Ibid., 1161b18.) Another way is according to the relation of the effect to its principle, and this is the relation of son to father; thus he says that children love their parents, because they exist from them. (Ibid., 1161b29.) The third is according to the mutual relation of those who share one principle, as brothers are said to be born from the same people, as he himself says in the same place. (Ibid., 1161b30.)

And since a point moved makes a line, and by propagation in a certain way the father descends into the son, for this reason three lines of consanguinity are taken according to the three relationships mentioned, namely, the line of descent according to the first relationship, the line of ascent according to the second relationship, and the collateral line according to the third relationship. But since the movement of propagation does not come to rest in one terminus, but progresses further, for this reason we find that every father has his own father and a son, his own son, and so on in succession; and according to these different steps, different degrees are found in one line. And since the degree of anything is some part of that thing, the degree of close relationship cannot be where there is no close relationship; and thus, either identity or extreme distance remove the degree of consanguinity, for nothing is closely related to itself, as neither is it like itself. And because of this no person makes any degree by himself, but only when compared to another person.

But nevertheless, there are different formulae for calculating degrees in different lines. For a degree of consanguinity in the line of ascent is contracted by the fact that one person whose consanguinity is being considered, is descended from someone else: and thus, according to canonical (See Arbor consanguinitatis (RF I, 1425–26), and John of Andrew’s Declaratio (RF I, 1427).) and legal (See Digests, Bk. 38, tit. 10, leg. 1, ‘Gradus.’) calculation, the person who comes first in the process of propagation, whether by ascending or descending, is removed from the other, say from Peter, in the first degree, like a father and a son. But the ones who come second are removed in the second degree, like a grandfather and grandson, and so on in succession. But the consanguinity of those who are in the collateral line is contracted not from the fact that one of them is propagated from the other, but because both are propagated from one person; and thus the degree in this line of consanguinity is calculated by comparison to the one principle from which both are propagated.

But according to this there is a different canonical calculation from the legal calculation: (See, in addition to the aforementioned authorities, Gratian, Decretals, pt. 2, cause 35, q. 5, can. 2, ‘Ad sedem,’ sec. 4.) for the legal calculation counts descent from a common root on both sides; but the canonical calculation only counts it on the side where the greater number of degrees is found; thus according to the legal computation a brother and a sister, or two brothers, are related to each other in the second degree, for they both are removed from the common root by one degree; and likewise, the sons of two brothers are removed from each other in the fourth degree. But according to the canonical calculation, two brothers are related to each other in the first degree, for neither of them are removed from the common root except by one degree; but the son of one of the brothers is removed from the other brother in the second degree, for that is how distant he is from the common root.

And thus according to the canonical calculation, by the same degree that someone is removed from someone higher, he is removed from anyone descended from him, and never less: for whatever is the cause of a thing being the way it is, is yet more so. (See Aristotle, Posterior Analytics, Bk 1, ch. 2 (72a29).) This is why if other descendants from a common ancestor are connected with someone by reason of the common ancestor, they cannot be closer relatives to the one descended from another side than the ancestor himself is. But sometimes someone is more removed from someone descended from his common ancestor than he is from the ancestor, for the other may be more removed from the common ancestor than he is; and consanguinity has to be computed according to the more remote distance.

Reply Obj. 1: That objection proceeds on false grounds. For consanguinity is not a series, but a certain relation of some persons to each other, whose series makes the line of consanguinity.

Reply Obj. 2: Descent, taken generally, can be found in the consideration of any line of consanguinity: for physical propagation, by which the bond of consanguinity is contracted, is a certain descent; but only one kind of descent, i.e., from a person whose consanguinity is in question, makes the line of descendants.

Reply Obj. 3: A line can be taken in two ways. Sometimes properly, for that dimension which is the first species of continuous quantity; and in this way, a straight line contains only two points in act, which terminate it, but it has infinite points in potency, any of which that are marked will divide the line in act, and two lines will be made. At other times, though, line is taken to mean those things that are disposed linearly; and according to this meaning line and figure are attributed to numbers, inasmuch as a unit is placed after a unit in some number, and in this way any unit added makes a degree in this kind of line; and it is the same way with the line of consanguinity; and for this reason one line contains several degrees.

Reply Obj. 4: Just as likeness cannot exist where there is no diversity, so also close relationship cannot exist where there is no distance; and therefore not every kind of distance is opposed to consanguinity, but only that distance that excludes the closeness of consanguinity.

Reply Obj. 5: Just as whiteness can be called ‘greater’ in two ways, in one way from the intensity of its quality, and in another way from the quantity of its surface, so also consanguinity is called ‘greater’ or ‘lesser’ in two ways. In one way, intensively, from the nature of the consanguinity itself; in another way, dimensively, as it were; and in this way the quantity of consanguinity is measured from the persons between whom the propagation of consanguinity proceeds, and in this second way the degrees in consanguinity are distinguished. And thus it happens that of two people who are in the same degree of consanguinity with respect to a third person, one is more consanguineous to him than the other by considering the first quantity of consanguinity: as a father and brother are related to someone in the first degree of consanguinity, for on neither part does some other person come in the middle; but nevertheless, intensively speaking, someone’s father is connected to him more than his brother, for a brother is not connected to someone except inasmuch as they have the same father. And therefore, the closer someone is to the common principle, from which consanguinity descends, the more consanguineous he is, although he may not be in a closer degree, and according to this a great-uncle is closer to someone than his great-nephew, although they are in the same degree.

Reply Obj. 6: Although a father and a paternal uncle are in the same degree with respect to the root of consanguinity, for both are removed one degree from the grandfather, nevertheless with respect to the person whose consanguinity is in question, they are not in the same degree; for the father is in the first degree, but the paternal uncle cannot be closer than the second degree, in which the grandfather is.

Reply Obj. 7: Two persons are always removed in an equal number of degrees from each other, even though they are not always removed in an equal number of degrees from the common forebear, as is clear from what has been said.

Article 3

Whether in some degrees it impedes marriage by natural law

Obj. 1: To the third question, we proceed thus. (Parallel: ST II-II, q. 154, a. 9; SCG III, ch. 125; Super I Cor. 5, lec. 1.) It seems that consanguinity does not impede marriage by natural law. For no woman can be closer to a man than Eve was to Adam, about whom Genesis 2:23 says, here now is bone of my bones, and flesh of my flesh. But Eve was joined in marriage to Adam. Therefore, no consanguinity impedes marriage, as far as the law of nature goes.

Obj. 2: Furthermore, natural law is the same among all men. But in barbarous nations no persons joined by blood ties are excluded from marriage. Therefore, consanguinity does not impede marriage, as far as the law of nature goes.

Obj. 3: Furthermore, natural law is what nature has taught all animals, as is said in the beginning of the Digests. (Digests, Bk. 1, tit. 1, leg. 1, ‘Iuri operam.’) But brute animals also copulate with their mothers. Therefore it is not of the law of nature that some person be barred from marriage because of consanguinity.

Obj. 4: Furthermore, nothing impedes marriage that is not contrary to some good of marriage. But consanguinity is not contrary to any good of marriage. Therefore, it does not impede it.

Obj. 5: Furthermore, those things that are more closely related and similar have a better and stronger union. But marriage is a certain kind of union. Therefore, since consanguinity is a certain kind of closeness, it does not impede marriage, but rather helps it.

On the contrary (1), that which impedes the good of offspring also impedes marriage, according to the law of nature. But consanguinity impedes the good of offspring; for as is said in the text from the words of Gregory, we have learned by experience that from such a conjugal union progeny cannot grow up. (Gregory the Great, Register, Bk. 11, indict. 4, epist. 44 ad Augustinum, ad interrog. 6 (PL 87:1189).) Therefore, consanguinity impedes marriage according to the law of nature.

Furthermore (2), what human nature had in its first condition is of natural law. But from its first condition nature held that father and mother were excluded from marriage; which is clear by what is said in Genesis 2:24, because of this a man leaves his father and mother; which cannot be understood with respect to living together, and thus it is necessary to understand it with respect to the union of marriage. Therefore consanguinity impedes marriage according to the law of nature.

I answer that, as was said above in the corpus of Distinction 33, Question 1, article 1, what is said to be against the law of nature in marriage is what renders marriage inadequate to the end for which it was ordained. But the end of marriage, first and per se, is the good of offspring; which indeed is impeded by a certain consanguinity, namely between father and daughter or between son and mother. Not indeed that this end would be totally destroyed, for a daughter can conceive children by the seed of her father, and likewise with her father she may nurture and instruct them, and this is what the good of offspring consists in. But rather it would not be done in an appropriate manner. For it is disordered that a daughter should be joined to her father in marriage as a partner for the sake of generating and educating children, when it is necessary for her to be subject to her father in all things as to the one from whom she proceeds; and therefore it is of natural law that the father and mother are barred from marriage, and even more the mother than the father; for more of the reverence that is owed to parents is diminished if the son takes his mother to wife than if the father takes his daughter, for a wife should be in a certain way subject to her husband. But the secondary essential end of marriage is simply the repression of concupiscence, which is lost if any consanguineous woman can be taken in marriage; for a great opportunity is presented to concupiscence unless physical intimacy is forbidden between those persons who have to keep company in the same house.

And therefore divine law (See Leviticus 18.) does not only exclude father and mother from marriage, but also other related persons with whom it is necessary to live at the same time, and who have to guard each other’s purity. And divine law gives this as a reason, saying in Leviticus 18:10, nor shall you reveal the nakedness of such or of such, for it is your nakedness. But per accidens, the end of marriage is the confederation of men, and the multiplication of friendship, when a man takes his wife’s relatives as his own; and thus it would be detrimental to this multiplication of friendship if someone could take as his wife a woman joined to him by blood, for by this no new friendship would be built up by the marriage. And thus according to human laws (Institutes of Justinian, Bk. 1, ti. 10, secs. 1–3, 5–7, 9–10.) and statutes of the Church (See Gregory IX, Decretals, Bk. 4, tit. 14, ch. 3, ‘Quod dilectio’; ch. 8, ‘Non debet’; Gratian, Decretals, pt. 2, cause 35, qq. 2 and 3, can. 16 ‘Progeniem’.) many degrees of consanguinity are barred from marriage. So therefore, it is clear from what has been said that consanguinity impedes marriage for certain persons by natural law; for others it is by divine law; and for others it is by the law instituted by men.

Reply Obj. 1: Although Eve proceeded from Adam, she was nevertheless not the daughter of Adam; for she did not proceed from him in the way that a man is able to generate someone like himself in species, but by a divine operation; for thus one who was an equal could be made from the rib of Adam, as Eve was made. And thus there is not such a natural congruence of Eve to Adam as of a daughter to a father, nor is Adam the natural principle of Eve, as a father is of a daughter.

Reply Obj. 2: It does not come from natural law that certain barbarians commingle carnally with their parents, but from the ardor of concupiscence, which obscures the law of nature in them.

Reply Obj. 3: The union of a husband and wife is said to be of natural law because nature teaches all animals this; but it teaches this union to different animals in different ways, according to their different conditions. Now, carnal intercourse diminishes the reverence that is owed to parents. For nature endows parents with concern for providing for their children, just as it endows children with reverence for their parents. But it endows no other genus with concern for children or reverence for parents at all times, except for man; but with other animals, less or more, according to how necessary the children are to their parents or the parents to their children; and so also among certain animals the sons abhor knowing their mothers carnally, as long as recognition of their mothers remains in them with a certain reverence for them, as the Philosopher notes of the camel and the horse in Book 9 of the History of Animals. (Aristotle, History of Animals, Bk. 9, ch. 47.) And since all the decent habits of animals are naturally brought together in men, and more perfectly in them than in others, this is why man naturally abhors knowing carnally not only the mother, but also the daughter, which is still less contrary to nature, as was said; and again, among other animals consanguinity is not contracted by propagation of the flesh, as among men, as was said; and therefore the argument is not parallel.

Reply Obj. 4: From what has been said, it is already clear how consanguinity of the spouses is contrary to the good of marriage; and so the argument proceeds on false grounds.

Reply Obj. 5: It is not unfitting for one of two unions to be impeded by the other; for just as where there is identity there is not likeness, so also the bond of consanguinity can impede the union of marriage.

Article 4

Whether the degrees that impede marriage can be determined by the statutes of the Church

Obj. 1: To the fourth question, we proceed thus. It seems that the degrees of consanguinity that impede marriage could not be fixed by the Church up to the fourth degree. For in Matthew 19:6 it says, what God has joined, let man not separate. But those who are joined within the fourth degree of consanguinity, God has joined, for their union is not prohibited by divine law. Therefore, they should not be separated by human statute.

Obj. 2: Furthermore, marriage is a sacrament, just as baptism is. But it cannot happen by Church statute that the one who approaches baptism would not receive the baptismal character, if the person, by divine law, were capable of it. Therefore, neither can the statute of the Church make it so that marriage would not exist between those who are not prohibited by divine law from being joined matrimonially.

Obj. 3: Furthermore, positive law cannot remove or increase those things that are natural. But consanguinity is a natural bond, which in itself does not necessarily impede marriage. Therefore, the Church cannnot by a certain statute make it be the case that some people can be joined or not joined matrimonially, just as it cannot make them consanguineous or not consanguineous.

Obj. 4: Furthermore, the statute of positive law must have some reasonable cause, for it is according to its reasonable cause that it proceeds from natural law. But the causes that are assigned for the number of degrees seem to be entirely unreasonable, for they have no relation to what is caused. For example, that consanguinity is prohibited up to the fourth degree because of the four elements, (Gregory IX, Decretals, Bk. 4, tit. 14, ch. 8, ‘Non debet.’) up to the sixth degree because of the six ages of man, (Gratian, Decretals, pt. 2, cause 35, q. 4, can. 1, ‘Consanguinitas.’) up to the seventh degree because of the seven days in which all time is measured. (Peter Lombard, Sentences, Bk. 4, d. 40, ch. 3 (QR II:981).) Therefore, it seems that such a prohibition as this has no strength.

Obj. 5: Furthermore, where there is the same cause, there must be the same effect. But the reason that consanguinity impedes marriage is the good of offspring, the repression of concupiscence, and the multiplication of friendship, as is clear from what has been said, (In the preceding article.) and these things are equally necessary at all times. Therefore at all times marriage should have been impeded by equal degrees of consanguinity, which is not the case; for currently consanguinity impedes marriage up to the fourth degree, while formerly, up to the seventh. (Gratian, Decretals, pt. 2, cause 35, qq. 2 and 3, can. 16 ‘Progeniem.’)

Obj. 6: Furthermore, one and the same union cannot be in the genus of sacrament and in the genus of illicit sexual intercourse. But this would happen if the Church had the power of establishing a different number of degrees that would impede marriage. For if some couple were related in the fifth degree, when it was prohibited, such a union would be illicit sexual intercourse. But afterward when the Church revoked the prohibition, the same union would be a marriage; and by the converse, it could happen if some degrees were allowed by the Church, and afterward were forbidden. Therefore it seems that the power of the Church does not extend to this.

Obj. 7: Furthermore, human law should imitate divine law. But according to divine law, which is contained in the Old Law, the prohibition of degrees does not run equally above and below; for in the Old Law someone was prohibited from taking the sister of his father to wife, (Leviticus 18:12.) but not the daughter of his brother. (Joshua 15:15.) Therefore, neither should any prohibition remain today regarding uncles and aunts and nieces and nephews.

On the contrary (1), the Lord said to his disciples in Luke 10:16: he who hears you, hears me. Therefore, the precept of the Church has the same strength as the precept of God. But the Church has sometimes prohibited and sometimes allowed certain degrees that the Old Law did not prohibit. Therefore, these degrees impede marriage.

Furthermore (2), just as at one time the marriages of the gentiles were dispensed by civil laws, so now they are by the statutes of the Church. But formerly the civil law (Institutes of Justinian, Bk. 1, tit. 10, sec. 1, ‘Ergo non omnes.’) determined which degrees of consanguinity impede marriage and which ones do not. Therefore, this can also be done now by the statutes of the Church.

I answer that, in keeping with different times, consanguinity has impeded marriage at different degrees. For in the beginning of the human race only the father and mother were barred from marriage to their children, for at that time there was a scarcity of men, and it was necessary to expend the greatest care for the propagation of the human race; and thus no one was to be excluded except those persons who were inadmissible to marriage according to the chief end of marriage, which is the good of offspring, as was said. (In the preceding article.)

But after the human race had increased, many persons were ruled out by the law of Moses, (See, for example, Leviticus 18.) which already began to restrain concupiscence; for which reason, as Rabbi Moses (Moses Maimonides, Guide for the Perplexed, pt. 3, ch. 49 (FR 376).) says, all those persons were barred from marriage who were accustomed to live together in one family; for if physical intimacy could legally take place among them, it would have presented a great incentive to sensual desire. But the Old Law permitted other degrees of consanguinity; indeed, in a certain way, it even commanded them, as, for example, each man took his wife from among his blood relations, so that there would be no confusion about the succession; (Numbers 36:6.) for in those days the divine worship was propagated by the succession of the race.

But afterward, in the New Law, which is a law of spirit and love, many degrees of consanguinity were prohibited, for now by spiritual grace, not by physical origin, worship is handed on and increased. This is why people had to be withdrawn more from physical things to be free for the spiritual things, and so that love would be diffused more widely. And so, in ancient times it was impeded up to more distant degrees of consanguinity, so that for many, a natural friendship would endure because of consanguinity and affinity; and reasonably up to the seventh degree, both because memory of the common root was not easily retained beyond the seventh degree, and because it corresponded to the sevenfold grace of the Holy Spirit.

But afterward, in recent times, the prohibition of the Church was restricted to the first four degrees, for it was useless and dangerous to prohibit the degrees of consanguinity beyond that. Useless indeed, for to more remote blood relatives there is hardly any bond of greater friendship than to strangers, with charity growing cold in many hearts. It was dangerous, moreover, because while concupiscence and negligence were prevailing all the same, men did not keep track of the great number of their blood relations. And in this way a snare of damnation was hurled into the path of many by the prohibition of the more remote degrees of consanguinity. And the prohibition mentioned, reaching to the fourth degree, is appropriately strict enough, both because people are accustomed to living together up to the fourth generation, and so the memory of consanguinity cannot be effaced, for which reason the Lord threatens that the sins of the parents will be visited upon the sons up to the third and fourth generation; and because in any generation the mixture of blood, which causes consanguinity when it is the same, is newly combined with the blood of others; and to the degree that it is mixed with others, it is removed from the first ones. And since there are four elements, of which any one is more easily mixable to the degree that it is finer, consequently in the first commingling, the identity of the blood is diluted as concerns the first element, which is the most subtle; in the second commingling, as to the second element; in the third, as to the third element; in the fourth, as to the fourth element; and thus carnal union can fittingly happen again after the fourth generation.

Reply Obj. 1: Just as God does not join those who are joined against the divine precept, so he does not join those who are joined against the precept of the Church, which has the same power of obliging as divine precept.

Reply Obj. 2: Marriage is not only a sacrament, but also an office; and thus it is more subject to the ordering of the ministers of the Church than baptism, which is only a sacrament; for spiritual contracts and duties are determined by the laws of the Church just as human contracts and duties are determined by human laws.

Reply Obj. 3: Although the bond of consanguinity is natural, nevertheless it is not natural that consanguinity impede carnal intimacy, unless according to a certain degree, as was said; (In the preceding article.) and thus the Church does not make its own decree that certain people are or are not consanguineous, for in every age they remain equally consanguineous; but it decrees that carnal intimacy is licit or illicit in different degrees of consanguinity according to different times.

Reply Obj. 4: Arguments such as those ascribed are given more in the mode of fittingness and proportion than in the mode of cause and necessity.

Reply Obj. 5: From what has been said, it is already clear that there is not the same reason for prohibiting degrees of consanguinity at different times; for which reason what is conceded as practical at a certain time may be more wholesome to prohibit at another.

Reply Obj. 6: A statute does not have to do with what is past, but with the future; for which reason, if at one time the fifth degree were to be prohibited, which is now allowed, those who are now joined in the fifth degree need not be separated, for no subsequent impediment to marriage can invalidate it; and so the union that was a marriage before would not become incestuous by the statute of the Church. Likewise, if a certain degree were to be permitted which is now prohibited, that union would not become matrimonial by the statute of the Church by reason of the first contract, for they could separate if they wished; but nevertheless they could contract again, and that would be another union.

Reply Obj. 7: In prohibiting degrees of consanguinity, the Church particularly attends to the reason of love; and since there is not less reason of love for a grandson than for a paternal uncle, but rather a greater one—as a father is said to be closer to his son than the son to his father in the Ethics 8 (Aristotle, Nicomachean Ethics, Bk. 8, ch. 12 (1161b19).)—because of this it prohibits the degrees of consanguinity equally among uncles and grandsons. But in prohibiting persons the Old Law attempted to restrict concupiscence especially as regards cohabitation, by prohibiting those persons to whom the access was more easily open because of living together. But it is more customary for a granddaughter to live together with an uncle than for an aunt to live with a grandson; for a daughter is almost the same with her father, since she is something of his; but a sister is not in this way the same as her brother, since she is not something of his, but rather born from the same; and thus there was not the same reason for prohibiting a niece and an aunt.

Exposition of the Text

Because he does not count the trunk among the degrees. (Sententiae IV, 40.2 (225). 1.) He calls the root of consanguinity the trunk, which is the father of sons. But the principle of a certain genus can be taken in two ways. In one way, the principle is what is in that genus, as if we say the first part of a line is the principle. In another way, the principle is what does not receive the predication of the genus, as the principle of a line is said to be a point; and in this way the principle and root of consanguinity can be said in two ways. In one way the first person himself by whom consanguinity is said, which person is not consanguinity, but the principle of consanguinity; and according to this, a son who is removed from the person of his father makes the first degree of distance, and the son of the son makes the second, and so on in succession. In another way, the first consanguinity is what is the cause of every other consanguinity; and thus the very consanguinity that is between father and son is established as the root, and according to that the father and son are counted as one principle, from whom the son of the son is removed by the first consanguinity; and thus this distance makes the first degree and so on in succession; and according to the degrees are calculated in different ways in the text. But the first way of calculating is more in common use.

“Just as the generation of the world and of the state of man is terminated at six ages, so also the relationship of kinship should be terminated at so many degrees.” (Sent. IV, 40.3 (226). 1, Isidore Etymologiae, bk 9 c6 n29.) In the world, the ages are not assigned as to substance, for this will endure in perpetuity, but as to state, for thus the world will pass away, and thus it grows old and declines; and according to this the ages of the world are distinguished metaphorically by their likeness to the age of one man. For the ages in man are differentiated according to different notable changes in his states. For this reason, the first age is called infancy, up until the seventh year; the second, childhood, is up to the fourteenth year; the third, adolescence, to the twentieth year; which three ages are sometimes counted as one; the fourth is youth up to fifty years; the fifth age is mature age, to seventy years; the sixth is old age, until the end. And similarly, in the world, the first age is said to be from Adam until Noah, in which the institution of the human race and the fall took place; the second from Noah to Abraham, in which the destruction of the human race by the flood and its renewal took place; the third from Abraham to David, in which the institution of circumcision happened; the fourth from David until the exile in Babylon, in which the law flourished under the kings and prophets; the fifth from the exile in Babylon until Christ, in which the captivity and liberation of the people occurred; the sixth from Christ until the end, in which there is the redemption of the human race. But nevertheless, it is not necessary that the ages of the human race be completed by an equal number of years, since neither are the ages of one man; for the last age of man sometimes has as much as all the previous.