I. Reply to the question
Ordinatio IV, d. 33, q. 1
"Was plural marriage ever licit?"
Regarding question 1, arguments for the negative:
Plural marriage is contrary to the natural law and contrary to the original institution of marriage. This is proved from what is said in Genesis 2:24, "They shall be two in one flesh," which expressed the natural law concerning marriage; therefore, it neither is nor was licit for someone to have more than one wife. It is also proved from an interlinear gloss on Genesis 4:19 concerning Lamech, who "took two wives." The Gloss says that Lamech "was the first to introduce plural marriage, which is contrary to the natural law."
Also, it was never licit for a woman to have two husbands;1 therefore, it was also never licit for a man to have two wives. Proof of the inference: a man and a woman are judged equal with respect to conjugal acts according to 1 Corinthians 7:3–4.
Arguments for the affirmative:
According to Genesis 16, Abraham had Sarah and Hagar and Keturah;2 and we read in Genesis 29:18–30:24 that Jacob had two wives and in 2 Kings 5 that David had many wives and concubines. Now it is not probable that these holy patriarchs did something illicit in entering into such marriages. Therefore, etc.
Also, Augustine endorses this view near the end of On the Good of Marriage [25.33]:
"For the righteous men of old it was not a sin to have recourse to more than one woman, nor were they acting contrary to nature in this, since they did so for the sake of begetting children. It was contrary neither to law nor to morals, since in those days it was not prohibited by any law."
I. Reply to the question
The first thing we need to investigate here is what is required for strict commutative justice in the marriage contract on the part of the contracting parties, and what,
1 I omit Scotus's biviria, ut ita loquar, which suggests a nonce-word on the model of bigamia ("plural marriage"), but substituting vir, "man," for gam- (from the Greek gamos, "marriage").
2 Genesis 11:29, 16:1–15, 25:1–2.
WAS PLURAL MARRIAGE EVER LICIT?
beyond that, is added for complete justice in such a contract on the part of a superior. The second is what in a given case suffices for justice as far as the topic of this question is concerned, and how such a contract becomes sufficient and completely just.
A. What is required on the part of the contracting parties for strict commutative justice in a marriage contract
9 On the first topic I say that in every exchange, as far as the parties to the exchange and what they exchange are concerned, strict justice requires that what they exchange be of equal value, to the extent possible, for the end on account of which the exchange is made.
10 Now the exchange in the marriage contract is made for two purposes: the procreation of children and the avoidance of fornication.
11 A man's body is of greater value than a woman's for the first purpose, since in a given period of time one man can impregnate many women, but one woman cannot conceive by as many men. So as far as this end is concerned, plural marriage— such that a man exchanges his body for the bodies of as many women as he can impregnate, in such a way as a man can impregnate them—is evidently in accord with strict justice.3 Yet there would not have been plural marriage in the state of innocence, when marriage was strictly for the purpose [of procreation], since there was no necessity4 then that a man should exchange his body with many women for the sake of procreating, since there would have been sufficient procreation through the simple exchange of one man and one woman, since neither man nor woman would have been sterile then.
12 With respect to the second end, that of avoiding fornication, which applies only in the state of fallen nature, a man's and a woman's body are of equal value.
13 And therefore, in the state of fallen nature, strict justice in the marriage contract as considered in relation to both ends requires the exchange of one body for one body.
14 I add that there is no completion of justice in this exchange apart from the authority of a superior who institutes or approves such and such an exchange. For even if inferiors have ownership of certain things, it is the lawgiver who licitly determines whether such and such an exchange is just,5 and all the more so in the present case as 3 A alone of the collated MSS adds the following sentence: "Hence, it is not contrary to nature in other animals that one male has more than one female."
4 Reading with PZN. The edition, following A, has "Yet there was not and would not have been plural marriage in the state of innocence, when marriage was and would have been strictly for the purpose [of procreation], since there would have been no necessity."
5 Reading tamen commutatio earum licite determinatur talis vel talis iusta a legislatore (ZN) for the edition's tamen commutatio earum licita, talis vel talis, determinatur iusta a legislatore (A).
ORDINATIO IV, D. , Q.
regards the mutual exchange of bodies with reference to the lawgiver who is God.
Now in both the state of innocence and the state of fallen nature God instituted the rule that this exchange of bodies should be of one body for one body, and so complete justice consists in that.
B. What suffices for justice in a given case, and how such a contract becomes sufficient and completely just
On the second topic I say that a dispensation is a clarification of a law or a revocation of a law. For God could clarify his law concerning this exchange or revoke it in a given case—and reasonably so in a case in which revoking the law produces a greater good than observing it.
Now at a time when it was necessary that the human race be increased, either unqualifiedly or for the sake of the worship of God—because there were few worshipers of God, so it was necessary that the worshipers of God have as many children as possible, since faith and the worship of God endured only in them and their posterity—it was reasonable for God to make a dispensation and allow one man to exchange his body for the bodies of more than one woman so that there might be a greater increase in worshipers of God, and such an increase would not take place without such a dispensation. And in fact he did make such a dispensation, as we presume in the cases of Abraham and certain other patriarchs.
As for how justice in the marriage contract on the part of the contracting parties was preserved under this dispensation, I explain that as follows. When something is ordered toward two ends, a primary end and a secondary end, it is reasonable to make use of that thing in a way that is more conducive to the primary end even if that detracts somewhat from the secondary end. For example, food is efficacious for both pleasure, which is secondary, and nutrition, which is primary. According to right reason one should make use of food in a way that is more efficacious for nutrition, even if that is less efficacious for pleasure.
Now the marriage contract is both for repaying the marriage debt, so that one avoids fornication, as its secondary end, and for the good of offspring, as its primary end.
Therefore, according to right reason those who enter into the marriage contract ought to make this exchange in a way that is more efficacious for procreation, even if it is less efficacious for repaying the marriage debt. And this is done by exchanging the body of one man for the bodies of more than one woman. And as this is absolutely to be done, so in a case of necessity—when, that is, the primary end is extremely urgent—it is to be done necessarily; and in such a case the secondary end should be more or less disregarded.
And it is clear from this how there is justice on the part of the contracting parties, because according to right reason each party ought to will to yield something of his or