I don’t see how my wife would be any less offended and wronged by my decision to marry a mistress than simply to keep one, and so polygamy seems to be just institutionalized adultery. Since institutional adultery seems in direct contradiction to even the loosest broadly acceptable view of marriage (even the most progressive legal accounts of a marriage, for example), polygamy cannot be allowed, Q.E.D.

But by now we all know the template of the response to claims like this. There’s certainly some non-zero percentage of the population that falls somewhere on the spectrum from open to polygamy all the way up to feeling that they need polygamy to live a fulfilled life, and so the argument I just gave will be something between completely ineffectual and ridiculous to totally offensive. Again, laws against polygamy almost certainly drive some non-zero number of families underground, and who is confident enough in any abstract argument to make some child suffer for it?

For all that, I’m left with the sense that infidelity is wrong and that polygamy is infidelity. I’m stuck with the sense that there would be something wrong with my wife if I asked her If I could keep a mistress and she said “sure, if you marry her”. Such a wife wouldn’t understand something about being a wife, and she’d be degrading herself those who looked to her as modeling a role of what a wife is – and this would all remain true no matter what her feelings were on the matter. In fact, the more enthusiastic she was for the arrangement, the further she would be from understanding what she was. All one could read in her enthusiasm is a metric of self-imposed degradation, like a slaves who love their masters or a rape victims who are convinced the crime was totally their own fault. For her to be okay with polygamy is just a failure to understand the reality and importance of fidelity and the equality of spouses, not just for marriage but even for her own value as a person.



  1. thenyssan said,

    December 7, 2014 at 12:43 pm

    This makes me think of the surprising way Aquinas tackles the harm of adultery–the harm done to the potential offspring. It neatly avoids all our modern problems of “two consenting adults” but has its own difficulties. Since I teach this every year I’m in the position of coming up with ways to understand what this harm is, especially in light of the “what if they don’t have children?” objection. I’ve never really finished coming to grips with it.

    I suppose in some sense the harm is counterfactual. Take the child as an ens rationis and then the evil is this: “If this act were to result in this child (who would be harmed) I would do it anyway.” And to will evil on an innocent is evil, therefore etc.

    That still leaves open the question of what the harm really is. Being born into no family? Uncertainty of parentage? Predictable socio-economic disadvantages? Can we even agree on what those are?

    • December 7, 2014 at 1:08 pm

      It might be easier to teach that part of temperance from a policy rule approach and an individual exception approach. I have to teach that too this year and if I have to touch on those rules I’d first want to say “what should the policy be, keeping in mind that it as to deal with what happens for the most part?”

      I had some success teaching temperance through a study of addiction and the effects of pornography Patrick Fagan has a good PDF lit review on this at the Family Research Council website. Porn is particularly good at showing the nature of lust, and the data we have on it make it pretty indefensible even to the most skeptical.

    • December 7, 2014 at 7:30 pm

      I think putting it in terms of ‘harm’ makes it sound narrower than it is; Aquinas usually makes it sound as an inconsistency with the education of one’s child, which, of course, is part of the good of procreation itself, and he thinks of this education as very broad, and something continuing so long as both parent and child live (to the point that he holds that leaving a reasonable inheritance for one’s child, so far as one can, is included in it). Adultery in this sense is not merely a sexual sin; it is (one might say) to act in such a way that you will in a sense already and always be failing to do proper justice to any children you have. But this is only the injustice-like aspect of adultery, so to speak; the wrongness of adultery that it is an intemperance such that it makes an injustice of this sort possible. The wrongness in the adultery itself is that one is failing to restrain one’s pursuit of pleasure in light of the good of procreation (including the education of children). But procreation in this sense is a common good, which is why we can have any obligations about it at all; so there might well be an additional aspect to it: i.e., that it’s not just the good of potential children that is being shortchanged, but the common good of the human race, insofar as it includes care for children.

      I’ve always thought it interesting that whenever Aquinas can shift from talking about a sin in terms of temperance to talking about it in terms of justice, he does so, and, indeed, his discussion of temperance in ST seems to be set up precisely in order to make this possible. I think temperance itself is simply not a virtue that lends itself to hard and fast rules. This is not to say that there aren’t any, but it seems clearly to be a more naturally casuistic virtue than justice is. Justice very obviously deals directly with common good, and therefore with obligation; temperance only gets it in indirectly, being more focused on the mean relative to us and our circumstances. I think this is why the policy/exception approach has some traction.

      I worry sometimes, actually, that the focus on harm or injustice aspect of things, is perhaps the wrong thing for us to be doing in our day; what we need to be insisting on, I think, is that every pursuit of pleasure needs to be governed by more important things than pleasure itself. I think the failure to accept this — either by taking there to be nothing more important than pleasure (like Jeremy Bentham) or by being selective about which pursuits of pleasure need to be reined in or by taking pleasure as being in itself the default reason for doing things — is behind a very considerable portion of the dissoluteness of the modern age.

      • thenyssan said,

        December 8, 2014 at 11:56 am

        I really appreciate the comments and I very much agree with your points (especially your final, Brandon). Still, I have in mind ST I-II Q100 rather than the temperance material in ST II-II. In Q100 Aquinas makes two claims:

        1. The reason for adultery being in the Decalogue is that it harms our neighbor in deed through one united to him, viz. offspring (article 5).

        2. The precepts of the Decalogue are promulgated precisely because they are “low bar knowable”–even an uneducated man can easily know them and their reasons but since human judgment sometimes errs they are promulgated in law. Through these obvious ones, we understand the less obvious moral precepts which are known only to the wise (article 11)

        I find it fascinating that Aquinas would claim that about the reason for adultery, since we would never think of it (perhaps because of our dissoluteness). I’m almost tempted to say that Aquinas thinks the intemperance angle is less obvious and more a matter for the wise. But I think now I’m just trying to be provocative.

        Thanks for the thoughts. It will help when I’m putting some things together this Christmas break.

      • December 8, 2014 at 12:30 pm


        What do you think about some of the modern ways of relating sexual pleasure to a common good or something beyond pleasure? Here I’m thinking of anti-natalist arguments (appeals to overpopulation or the fact that we now need to have fewer than six kids to make sure two survive) or the various ontologies of orientation (given that I’m an X, it is good for me to act X-wise). As I’ve put the anti-natalist argument here it would need to be tuned up to say anything about temperance, but I think it can get there.

      • December 8, 2014 at 4:09 pm


        I think anti-natalists in general run into a problem of not treating procreation of children as a genuine common good. I think one could have a temperance-based argument, taking some of the anti-natalist concerns into account; but this won’t get an obligation not to have children, but an obligation to restrain oneself in pursuit of sexual pleasures so as to help deal with overpopulation, etc. — and the latter is far weaker than any actual anti-natalist position.

        The orientationist arguments are somewhat different. I’ve never run into one that did not, in fact, boil down to an exaltation of pursuit of pleasure (or preference-satisfaction, or self-fulfillment interpreted subjectively, which amount to the same thing in this context). But I think the real difficulty for such arguments is not there: even if one posits that actions of this kind are real objective goods, I think it becomes unclear how they could genuinely be common good. Certainly they are not obviously common goods in the way having preserving the human species, biologically and culturally, is a common good of the entire human race. To be a common good, it has to be a good in which we all share; your having children is a good for me as well as for you, and for people all the way around the world, even if it’s not, itself, one of the most obviously salient goods in my life, or the life of someone in India — as far as common good is concerned it is a small contribution among millions of contributions. But it is a definite, definable contribution. I’ve yet to see any clear statement of how someone’s acting X-wise, in one of these orientationist arguments, actually contributes to everyone’s good in being a member of the human race. And I’m not sure how one could possibly do that without bordering on the most raging kind of narcissism. I think regardless of the X, it just ends up being exactly parallel to (and sometimes just the same as) an argument for fornication based on the fact that human beings generally tend to sex — that’s not a particularly impressive argument, since we also generally tend to restrain ourselves in sexual matters, since human sexuality must be rational.

  2. Hanan said,

    December 8, 2014 at 1:38 pm

    Infidelity is relations “outside” the legal bounds of the marriage. Once you broaden the legal bounds of a marriage it is no longer infidelity, so I am not sure how you can say it is. Not very biblical of you 😉

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