The Summa Theologica is written in a style that intends to help those who are studying to become priests or other religious ministers to the people. Its intent is to help them understand not just what the Catholic doctrine is, nor even just why it is what it is. Rather, it intends to make certain that they understand the substance of objections against that doctrine, good reasons why people might raise the objections, and why those objections have been refuted.
For that reason, it follows this form: It begins by questioning some aspect of doctrine (e.g., "Does God Exist?"). Then it breaks that question into several relevant forms. Then it offers evidence and argument in favor of the proposition that the Summa later intends to disprove. Generally these arguments are very good; in fact, we will be looking at one argument we may think is better than the response Aquinas gives.
Having raised very specific objections, Aquinas gives the doctrinal answer ("on the contrary....") and then explains the position of the Church. This detailed explanation is called the "corpus," or body of the response; here it is the part that begins "I answer that...." Then, finally, each question has specific responses to every one of the arguments raised against the doctrine.
So, let's look at two specific questions. The first one has to do with marriage as an element of natural law. (As most of you probably know, "Tully" here is Cicero; "The Philosopher" is Aristotle; )
Whether matrimony is of natural law?
Objection 1: It would seem that matrimony is not natural. Because "the natural law is what nature has taught all animals" [*Digest. I, i, de justitia et jure, 1]. But in other animals the sexes are united without matrimony. Therefore matrimony is not of natural law.
Objection 1: Further, that which is of natural law is found in all men with regard to their every state. But matrimony was not in every state of man, for as Tully says (De Inv. Rhet.), "at the beginning men were savages and then no man knew his own children, nor was he bound by any marriage tie," wherein matrimony consists. Therefore it is not natural.
Objection 3: Further, natural things are the same among all. But matrimony is not in the same way among all, since its practice varies according to the various laws. Therefore it is not natural.
Objection 4: Further, those things without which the intention of nature can be maintained would seem not to be natural. But nature intends the preservation of the species by generation which is possible without matrimony, as in the case of fornicators. Therefore matrimony is not natural.
On the contrary, At the commencement of the Digests it is stated: "The union of male and female, which we call matrimony, is of natural law."The parts in both bold and italic are my highlights.
Further, the Philosopher (Ethic. viii, 12) says that "man is an animal more inclined by nature to connubial than political society." But "man is naturally a political and gregarious animal," as the same author asserts (Polit. i, 2). Therefore he is naturally inclined to connubial union, and thus the conjugal union or matrimony is natural.
I answer that, A thing is said to be natural in two ways. First, as resulting of necessity from the principles of nature; thus upward movement is natural to fire. In this way matrimony is not natural, nor are any of those things that come to pass at the intervention or motion of the free-will. Secondly, that is said to be natural to which nature inclines although it comes to pass through the intervention of the free-will; thus acts of virtue and the virtues themselves are called natural; and in this way matrimony is natural, because natural reason inclines thereto in two ways. First, in relation to the principal end of matrimony, namely the good of the offspring. For nature intends not only the begetting of offspring, but also its education and development until it reach the perfect state of man as man, and that is the state of virtue. Hence, according to the Philosopher (Ethic. viii, 11,12), we derive three things from our parents, namely "existence," "nourishment," and "education." Now a child cannot be brought up and instructed unless it have certain and definite parents, and this would not be the case unless there were a tie between the man and a definite woman and it is in this that matrimony consists. Secondly, in relation to the secondary end of matrimony, which is the mutual services which married persons render one another in household matters. For just as natural reason dictates that men should live together, since one is not self-sufficient in all things concerning life, for which reason man is described as being naturally inclined to political society, so too among those works that are necessary for human life some are becoming to men, others to women. Wherefore nature inculcates that society of man and woman which consists in matrimony. These two reasons are given by the Philosopher (Ethic. viii, 11,12).
Reply to Objection 1: Man's nature inclines to a thing in two ways. In one way, because that thing is becoming to the generic nature, and this is common to all animals; in another way because it is becoming to the nature of the difference, whereby the human species in so far as it is rational overflows the genus; such is an act of prudence or temperance. And just as the generic nature, though one in all animals, yet is not in all in the same way, so neither does it incline in the same way in all, but in a way befitting each one. Accordingly man's nature inclines to matrimony on the part of the difference, as regards the second reason given above; wherefore the Philosopher (Ethic. viii, 11,12; Polit. i) gives this reason in men over other animals; but as regards the first reason it inclines on the part of the genus; wherefore he says that the begetting of offspring is common to all animals. Yet nature does not incline thereto in the same way in all animals; since there are animals whose offspring are able to seek food immediately after birth, or are sufficiently fed by their mother; and in these there is no tie between male and female; whereas in those whose offspring needs the support of both parents, although for a short time, there is a certain tie, as may be seen in certain birds. In man, however, since the child needs the parents' care for a long time, there is a very great tie between male and female, to which tie even the generic nature inclines.
Reply to Objection 2: The assertion of Tully may be true of some particular nation, provided we understand it as referring to the proximate beginning of that nation when it became a nation distinct from others; for that to which natural reason inclines is not realized in all things, and this statement is not universally true, since Holy Writ states that there has been matrimony from the beginning of the human race.
Reply to Objection 3: According to the Philosopher (Ethic. vii) "human nature is not unchangeable as the Divine nature is." Hence things that are of natural law vary according to the various states and conditions of men; although those which naturally pertain to things Divine nowise vary.
Reply to Objection 4: Nature intends not only being in the offspring, but also perfect being, for which matrimony is necessary, as shown above.
Aquinas says that there are two ways of being in accord with nature. The first is simply to be beholden to things like physics -- determination, in other words, by the laws of nature such as gravity. (Gravity is the most obvious example to us today, but was not to Aquinas; the example of fire's 'natural motion' upwards is taken from Aristotle's Physics.)
The other way is to direct your freely-chosen actions at the perfection of nature. Therefore virtue, and the virtues, are not only natural but the perfection of your nature. This is correct, because the virtues are virtues for everyone:
No matter what your goals, or your other moral values, courage is a virtue for you: it will help you achieve them. An ability to understand your duty and to command yourself to fulfill it will be useful to every man, and every woman, and every child. This moral reality is embedded in the structure of the world.Thus, for example, it is perfectly natural (in the first sense) for a man to desire to sleep with as many women as possible; there are certain physical drives, such as the operation of pheromones, that drive him to it. It is also very much in accord with natural law (in the second sense) to regulate the sexual urge so that he instead more perfectly completes it.
Why? Because the foremost point of sexuality is procreation; but the point of procreation is to produce not children but new adults. A man who is loyal to a wife is more likely not only to produce a child, but to raise it and educate it properly.
Notice that Aquinas defines this as the principle end of matrimony, and not just sexuality: thus, marriage is not chiefly about the happiness of the two married persons. This is close to the point I have been arguing -- that marriage is the creation of kinship bonds that unite bloodlines across generations. Aquinas puts more emphasis on the subsequent generation (the offspring) than I do; I think the duties to the previous generations are also very important. One has a duty to one's father, and to one's father-in-law; to one's mother, and mother-in-law; and to the memories and ideals of those who went before.
In any case, this is the foundation for marriage. Marriage is a kind of virtue. It is natural in the sense that it perfects nature.
Now, what about polygamy? Is that in accord with natural law, or not? As we shall see, the answer is, 'In one way yes, and in another, no.'
Whether it is against the natural law to have several wives?
Objection 1: It would seem that it is not against the natural law to have several wives. For custom does not prejudice the law of nature. But "it was not a sin" to have several wives "when this was the custom," according to Augustine (De Bono Conjug. xv) as quoted in the text (Sent. iv, D, 33). Therefore it is not contrary to the natural law to have several wives.Notice Objection 8 and its reply. This is the Golden Rule, which Aquinas defends as a general precept of natural law. Yet here he raises it precisely to explain why it shouldn't hold in this case. That's an oddity in several respects. The first is that the argument is irrelevant to his interests -- he is arguing against the inclusion of polygamous beliefs in a Christian community, and therefore why object to an argument from natural law that seems to reinforce his position?
Objection 2: Further, whoever acts in opposition to the natural law, disobeys a commandment, for the law of nature has its commandments even as the written law has. Now Augustine says (De Bono Conjug. xv; De Civ. Dei xv, 38) that "it was not contrary to a commandment" to have several wives, "because by no law was it forbidden." Therefore it is not against the natural law to have several wives.
Objection 3: Further, marriage is chiefly directed to the begetting of offspring. But one man may get children of several women, by causing them to be pregnant. Therefore It is not against the natural law to have several wives.
Objection 4: Further, "Natural right is that which nature has taught all animals," as stated at the beginning of the Digests (1, i, ff. De just. et jure). Now nature has not taught all animals that one male should be united to but one female, since with many animals the one male is united to several females. Therefore it is not against the natural law to have several wives.
Objection 5: Further, according to the Philosopher (De Gener. Animal. i, 20), in the begetting of offspring the male is to the female as agent to patient, and as the craftsman is to his material. But it is not against the order of nature for one agent to act on several patients, or for one craftsman to work in several materials. Therefore neither is it contrary to the law of nature for one husband to have many wives.
Objection 6: On the contrary, That which was instilled into man at the formation of human nature would seem especially to belong to the natural law. Now it was instilled into him at the very formation of human nature that one man should have one wife, according to Gn. 2:24,"They shall be two in one flesh." Therefore it is of natural law.
Objection 7: Further, it is contrary to the law of nature that man should bind himself to the impossible, and that what is given to one should be given to another. Now when a man contracts with a wife, he gives her the power of his body, so that he is bound to pay her the debt when she asks. Therefore it is against the law of nature that he should afterwards give the power of his body to another, because it would be impossible for him to pay both were both to ask at the same time.
Objection 8: Further, "Do not to another what thou wouldst not were done to thyself" [*Cf. Tob. 4:16] is a precept of the natural law. But a husband would by no means be willing for his wife to have another husband. Therefore he would be acting against the law of nature, were he to have another wife in addition.
Objection 9: Further, whatever is against the natural desire is contrary to the natural law. Now a husband's jealousy of his wife and the wife's jealousy of her husband are natural, for they are found in all. Therefore, since jealousy is "love impatient of sharing the beloved," it would seem to be contrary to the natural law that several wives should share one husband.
I answer that, All natural things are imbued with certain principles whereby they are enabled not only to exercise their proper actions, but also to render those actions proportionate to their end, whether such actions belong to a thing by virtue of its generic nature, or by virtue of its specific nature: thus it belongs to a magnet to be borne downwards by virtue of its generic nature, and to attract iron by virtue of its specific nature. Now just as in those things which act from natural necessity the principle of action is the form itself, whence their proper actions proceed proportionately to their end, so in things which are endowed with knowledge the principles of action are knowledge and appetite. Hence in the cognitive power there needs to be a natural concept, and in the appetitive power a natural inclination, whereby the action befitting the genus or species is rendered proportionate to the end. Now since man, of all animals, knows the aspect of the end, and the proportion of the action to the end, it follows that he is imbued with a natural concept, whereby he is directed to act in a befitting manner, and this is called "the natural law" or "the natural right," but in other animals "the natural instinct." For brutes are rather impelled by the force of nature to do befitting actions, than guided to act on their own judgment. Therefore the natural law is nothing else than a concept naturally instilled into man, whereby he is guided to act in a befitting manner in his proper actions, whether they are competent to him by virtue of his generic nature, as, for instance, to beget, to eat, and so on, or belong to him by virtue of his specific nature, as, for instance, to reason and so forth. Now whatever renders an action improportionate to the end which nature intends to obtain by a certain work is said to be contrary to the natural law. But an action may be improportionate either to the principal or to the secondary end, and in either case this happens in two ways. First, on account of something which wholly hinders the end; for instance a very great excess or a very great deficiency in eating hinders both the health of the body, which is the principal end of food, and aptitude for conducting business, which is its secondary end. Secondly, on account of something that renders the attainment of the principal or secondary end difficult, or less satisfactory, for instance eating inordinately in respect of undue time. Accordingly if an action be improportionate to the end, through altogether hindering the principal end directly, it is forbidden by the first precepts of the natural law, which hold the same place in practical matters, as the general concepts of the mind in speculative matters. If, however, it be in any way improportionate to the secondary end, or again to the principal end, as rendering its attainment difficult or less satisfactory, it is forbidden, not indeed by the first precepts of the natural law, but by the second which are derived from the first even as conclusions in speculative matters receive our assent by virtue of self-known principles: and thus the act in question is said to be against the law of nature.
Now marriage has for its principal end the begetting and rearing of children, and this end is competent to man according to his generic nature, wherefore it is common to other animals (Ethic. viii, 12), and thus it is that the "offspring" is assigned as a marriage good. But for its secondary end, as the Philosopher says (Ethic. viii, 12), it has, among men alone, the community of works that are a necessity of life, as stated above (Q, A). And in reference to this they owe one another "fidelity" which is one of the goods of marriage. Furthermore it has another end, as regards marriage between believers, namely the signification of Christ and the Church: and thus the "sacrament" is said to be a marriage good. Wherefore the first end corresponds to the marriage of man inasmuch as he is an animal: the second, inasmuch as he is a man; the third, inasmuch as he is a believer. Accordingly plurality of wives neither wholly destroys nor in any way hinders the first end of marriage, since one man is sufficient to get children of several wives, and to rear the children born of them. But though it does not wholly destroy the second end, it hinders it considerably for there cannot easily be peace in a family where several wives are joined to one husband, since one husband cannot suffice to satisfy the requisitions of several wives, and again because the sharing of several in one occupation is a cause of strife: thus "potters quarrel with one another" [*Aristotle, Rhet. ii, 4], and in like manner the several wives of one husband. The third end, it removes altogether, because as Christ is one, so also is the Church one. It is therefore evident from what has been said that plurality of wives is in a way against the law of nature, and in a way not against it.
Reply to Objection 1: Custom does not prejudice the law of nature as regards the first precepts of the latter, which are like the general concepts of the mind in speculative matters. But those which are drawn like conclusions from these custom enforces, as Tully declares (De Inv. Rhet. ii), or weakens. Such is the precept of nature in the matter of having one wife.
Reply to Objection 2: As Tully says (De Inv. Rhet. ii), "fear of the law and religion have sanctioned those things that come from nature and are approved by custom." Wherefore it is evident that those dictates of the natural law, which are derived from the first principles as it were of the natural law, have not the binding force of an absolute commandment, except when they have been sanctioned by Divine or human law. This is what Augustine means by saying that "they did not disobey the commandments of the law, since it was not forbidden by any law."
The Reply to the Third Objection follows from what has been said.
Reply to Objection 4: Natural right has several significations. First a right is said to be natural by its principle, because it is instilled by nature: and thus Tully defines it (De Inv. Rhet. ii) when he says: "Natural right is not the result of opinion but the product of an innate force." And since even in natural things certain movements are called natural, not that they be from an intrinsic principle, but because they are from a higher moving principle---thus the movements that are caused in the elements by the impress of heavenly bodies are said to be natural, as the Commentator states (De Coelo et Mundo iii, 28), therefore those things that are of Divine right are said to be of natural right, because they are caused by the impress and influence of a higher principle, namely God. Isidore takes it in this sense, when he says (Etym. v) that "the natural right is that which is contained in the Law and the Gospel." Thirdly, right is said to be natural not only from its principle but also from its matter, because it is about natural things. And since nature is contradistinguished with reason, whereby man is a man, it follows that if we take natural right in its strictest sense, those things which are dictated by natural reason and pertain to man alone are not said to be of natural right, but only those which are dictated by natural reason and are common to man and other animals. Thus we have the aforesaid definition, namely: "Natural right is what nature has taught all animals." Accordingly plurality of wives, though not contrary to natural right taken in the third sense, is nevertheless against natural right taken in the second sense, because it is forbidden by the Divine law. It is also against natural right taken in the first sense, as appears from what has been said, for such is nature's dictate to every animal according to the mode befitting its nature. Wherefore also certain animals, the rearing of whose offspring demands the care of both, namely the male and female, by natural instinct cling to the union of one with one, for instance the turtle-dove, the dove, and so forth.
The Reply to the Fifth Objection is clear from what has been said.
Since, however, the arguments adduced "on the contrary side" would seem to show that plurality of wives is against the first principles of the natural law, we must reply to them.
Accordingly we reply to the Sixth Objection that human nature was founded without any defect, and consequently it is endowed not only with those things without which the principal end of marriage is impossible of attainment, but also with those without which the secondary end of marriage could not be obtained without difficulty: and in this way it sufficed man when he was first formed to have one wife, as stated above.
Reply to Objection 7: In marriage the husband gives his wife power of his body, not in all respects, but only in those things that are required by marriage. Now marriage does not require the husband to pay the debt every time his wife asks for it, if we consider the principal end for which marriage was instituted, namely the good of the offspring, but only as far as is necessary for impregnation. But in so far as it is instituted as a remedy (which is its secondary end), marriage does require the debt to be paid at all times on being asked for. Hence it is evident that by taking several wives a man does not bind himself to the impossible, considering the principal end of marriage; and therefore plurality of wives is not against the first principles of the natural law.
Reply to Objection 8: This precept of the natural law, "Do not to another what thou wouldst not were done to thyself," should be understood with the proviso that there be equal proportion. For if a superior is unwilling to be withstood by his subject, he is not therefore bound not to withstand his subject. Hence it does not follow in virtue of this precept that as a husband is unwilling for his wife to have another husband, he must not have another wife: because for one man to have several wives is not contrary to the first principles of the natural law, as stated above: whereas for one wife to have several husbands is contrary to the first principles of the natural law, since thereby the good of the offspring which is the principal end of marriage is, in one respect, entirely destroyed, and in another respect hindered. For the good of the offspring means not only begetting, but also rearing. Now the begetting of offspring, though not wholly voided (since a woman may be impregnated a second time after impregnation has already taken place, as stated in De Gener. Animal. vii. 4), is nevertheless considerably hindered, because this can scarcely happen without injury either to both fetus or to one of them. But the rearing of the offspring is altogether done away, because as a result of one woman having several husbands there follows uncertainty of the offspring in relation to its father, whose care is necessary for its education. Wherefore the marriage of one wife with several husbands has not been sanctioned by any law or custom, whereas the converse has been.
Reply to Objection 9: The natural inclination in the appetitive power follows the natural concept in the cognitive power. And since it is not so much opposed to the natural concept for a man to have several wives as for a wife to have several husbands, it follows that a wife's love is not so averse to another sharing the same husband with her, as a husband's love is to another sharing the same wife with him. Consequently both in man and in other animals the male is more jealous of the female than "vice versa."
It's also unusual because Aquinas often argues against fairly clear Biblical passages that seem to create inequality between man and wife. He devotes an entire question to proving that men and women should be judged equally in cases of divorce due to adultery, e.g., that women should have the same rights to object to it and demand divorce as men. The objectors here have Biblical citations on their side, and not just Cicero! (Indeed, they do on this occasion as well -- the citation proving the Golden Rule is to the Book of Tobais, "Quod ab alio oderis fieri tibi," i.e., 'Don't do to others what you hate').
Aquinas isn't quite right to say that wives having many husbands has never been sanctioned by any law; and it's not clear that he's right to say that the education of the offspring is done away with in these cases. The Picts allowed women to take several sexual partners, and dealt with the resulting confusion about the fathers of children by deciding inheritance issues based on matrilineal lines, and raised the children in something like a communal fashion.
However, Aquinas might be right in saying that the practice is out of order with natural law, in this sense: it was exactly this custom of the Picts that led to their subjugation and destruction. The Scots (Scotti, in those days) coming from Ireland to places like Dal Riada, intermarried with the Picts, with the result that their daughters sent the family's wealth and position to the Scots; but their sons did not obtain any similar benefit from the Scots, who passed wealth and position to their sons. Therefore, by the time of Kenneth MacAlpin, the Picts were in a position to be utterly and permanently subjugated; today there is almost no trace of them.
Now, let's look at the corpus.
We begin again with an analogy to Aristotle's Physics. For most things besides people or animals, what is natural is determined by the form that inheres in the matter, e.g., the form of fire (which has the natural motion of going up) or the form of a magnet (which attracts or repels). For animals, there is similarly a natural instinct that directs them, without very much judgment on their part.
Human beings are different in that they are capable of learning from the forms they encounter, so that they can understand the purpose behind the form. Once they understand that, they can perfect nature. This is a particular capacity of human beings -- you might say it is the essential nature of human beings. What makes us men and not beasts is that we can order our lives toward virtue and the perfection of nature.
So, what is the end of marriage? Aquinas says there are three, but that they are not equally important.
The first is what we have already called "the principle end." Notice that this is the most important, even though the third end will prove to be about service to God as a member of the Christian world. Why is that the case? It is so because God made nature, and we are the only creatures that can understand the creation and perfect it: and therefore it is, you might say, our first duty to be perfectors of nature, sub-creators as Tolkien puts it.
Thus, anything that robs marriage of its 'principle end' is banned by natural law; but the secondary and tertiary ends are not banned by natural law. They are banned by religious law, which is also very important for Aquinas! The Medieval thinker believed that religious law should also be binding on us, so that for him there is no difference in outcomes; but in America, where we believe that religious law can only be accepted as a free choice, there might be.
That takes care of the first and third end, then. The principle end is undisturbed, and therefore polygamy in the sense of having several wives (or polygyny, as Elise likes to put it) is in accord with natural law. It is out of order for Christians, however.
The question, though, was about the Georgia school assignment related to Islamic polygamy. They don't have the problem that it is out of order with their faith; in fact, Islam is very specific in providing an order for it.
That leaves us with the second end, which is where we will have to decide the matter. Let's repeat it:
For its secondary end, as the Philosopher says (Ethic. viii, 12), it has, among men alone, the community of works that are a necessity of life, as stated above (Q, A).... Wherefore the first end corresponds to the marriage of man inasmuch as he is an animal: the second, inasmuch as he is a man; the third, inasmuch as he is a believer. ... [While polygamy] does not wholly destroy the second end, it hinders it considerably for there cannot easily be peace in a family where several wives are joined to one husband, since one husband cannot suffice to satisfy the requisitions of several wives, and again because the sharing of several in one occupation is a cause of strife: thus "potters quarrel with one another" [*Aristotle, Rhet. ii, 4], and in like manner the several wives of one husband.There are really two objections here. The first one is that the community within the household will not be as well ordered with a multitude of wives; it will be out of order as they quarrel or strive against each other. (This was Cassandra's objection, although she phrased it in terms not of the women quarreling, but of the man gaining undue power within the marriage by freedom to pit the wives against one another.)
The second is that "the community of works" in general may be disrupted. Aquinas doesn't go in to detail here, probably because he assumed that there was no chance of an outcome in which polygamy was really going to be licensed; but it is important for us. A common understanding of what a family is, and how it ought to be structured, is surely a key part of civilization. We need to know how to react to our neighbors, and we need the form to be well-ordered in this way as well. Not only does the marriage need to produce offspring, and perfect their upbringing (the end inasmuch as we are animals), it needs to provide a stable building block for our society (the end inasmuch as we are human beings). Inasmuch as we are Americans, we cannot stand on the third principle; whether or not that is a flaw in the American project, it is certainly at the core of that project.
It seems like it should be possible to build a rational argument on the ground provided by the second end, for those who wish to do so. Aquinas has been very helpful in laying out just what the principles are that underlie marriage. Let's discuss them, and see what we come up with from here.