If casual sex is permissible, so is polygamy

If casual sex is permissible, so is premarital sex. Now, on a view on which premarital sex is permissible, marriage is a complex normative institution that removes the right to have sex with others and confers on the spouses various duties—such as of loving, cherishing, honoring and caring for—to the other, as well as makes for at least a ceteris paribus commitment that the couple will strive to have a sexual relationship. (If premarital sex is impermissible, then marriage has one more normative component: it confers a permission for sex.)

But there need not be anything morally wrong with x's promising y that she will not have sex with anyone other than y and z. Promises of loving, cherishing, honoring and caring for another are a great thing when taken really seriously, and are simply a higher and deeper form of the commitment that we all have anyway to our friends, and there seems nothing wrong with making such promises to multiple people, as long as there are implicit or explicit rules on how apparent conflicts of love and care are to be resolved (a problem that is already anyway present in the case of a monogamous marriage, since it can come up with respect to duties to spouse and to children, since these can be in tension). The only component possibly problematic in the normative complex is the ceteris paribus commitment to a sexual relationship with multiple people. But it is hard to see what is wrong with that if casual sex is permissible. If it would be permissible for Jane to have sex with Sid and Roman on alternate days, why would it not be permissible for her to make a ceteris paribus promise to do so? This is particularly unproblematic if one thinks of marriage as permissibly dissoluble, as most people who think casual sex is permissible do.

So it seems that if casual sex is permissible, then the normative complex of commitments that constitutes marriage can be permissibly modified to a plural form. One may ask whether the modified version would still count as a marriage. If not, then polygamy is misnamed: it's not a plural marriage (poly-gamy) but a plural marriage-like relationship. But either way, we get the conclusion: If casual sex is permissible, so is polygamy.

An interesting question is whether we can prove the stronger claim that if premarital sex is permissible, so is polygamy. Probably not, since someone could think that premarital sex is permissible only in the context of a relationship with an exclusive commitment to one person. But if one thinks that something weaker than an exclusive commitment is sufficient for permissibility, maybe love, or maybe mutual respect (Martha Nussbaum), then one may still get the conclusion that polygamy is permissible.

Of course, the right conclusion to draw is that casual sex is impermissible.

Risk compensation

Rational decision theory predicts that decreasing the riskiness of a activity will tend to increase the prevalence and degree of risky activity. As paragliding is made safer, one expects more people to be engaged in paragliding and those who are engaged in it to do it more intensely. But of course increasing the prevalence and degree of behavior will tend to increase the prevalence of occurrences of the negative outcome that one was decreasing. This is the phenomenon of risk compensation: decreasing the risk of a negative outcome of an activity is to some degree—maybe sometimes completely—compensated for by an increase in the prevalence and degree of engagement in the risky activity. For instance, taxi drivers who have antilock brakes tend to follow the vehicle in front of them more closely.

Suppose that in some case the risk compensation to some safety measure is complete: i.e., the prevalence of the relevant negative outcome (say, crashes or fatalities) is unchanged, due to the compensating increase in the prevalence and degree of the risky behavior. One might think that at this point the safety measure was pointless.

Whether this conclusion is correct depends, however, on what values the risky behavior itself has when one brackets the risk in question. If the risky behavior has positive value when one brackets the risk, the safety measure does in fact achieve something good: an increase in prevalence and degree of valuable but risky behavior with no increase in negative outcome. Paragliding is (I assume) a pleasant way to enjoy the beauty of the earth and to stretch the limits of human ability. An increase in the prevalence of paragliding without an increase of negative outcomes is all to the good.

When the behavior is completely neutral, then the safety measure, however, is simply a waste given complete risk compensation.

Finally, if the risky behavior has negative value even when one brackets the particular risky outcome, then in the case where the risk compensation is complete, the safety measure is counterproductive. It does not decrease the negative outcome it is aimed at, but by increasing the prevalence of an otherwise unfortunate activity it on balance has a negative outcome. For instance, suppose bullfighting is an instance of immoral cruelty to animals. Then apart from the risks to the bullfighter, the activity has negative value: it harms the animal and damages the soul of the person. If a safety measure for prevention of goring then were compensated for by an increase in prevalence, the safety measure would have on balance a negative outcome: there would be no decrease in gorings but there would be an increase in immoral and harmful activity.

Moreover, in cases where the risky behavior has independently negative value, a safety measure can have on balance negative effect even when the risk compensation is quite modest. Suppose that (I am making up the numbers) gorings occur in 10% of bullfights and cruelty to bulls in 80%. Suppose, further, that cruelty to bulls is at least as bad as goring (since it not only harms the bull but more importantly it seriously damages the soul of the cruel person). Then a safety measure that decreases the probability of goring by a half but results in a modest 10% increase in the prevalence of bullfighting will have on balance negative effect. For suppose that previously there were 1000 bullfights, and hence 100 gorings and 800 instances of cruelty. Now there will be 1100 bullfights, and hence (at the new rate) 55 gorings and 880 instances of cruelty. We have prevented 45 gorings at the cost of 80 instances of cruelty, and that is not worth it.

Much of the public discussion of risk compensation and safety measures centers on sex, and particularly premarital sex. We should typically expect some behavioral change in the direction of risk compensation given a safety measure. If one thinks premarital sex to be itself typically valuable, then even given total risk compensation one will think the safety measure to be worthwhile. If one thinks premarital sex to be value-neutral, then as long as the risk compensation is incomplete (i.e., the decrease in the risks due to the safety measure is not balanced by the increase in prevalence), one will think the safety measure to be worthwhile (at least as long as the costs of the safety measure are not disproportionate). But if one thinks premarital sex to have negative moral value, then one may well think a safety measure to be counterproductive even if the risk compensation is incomplete—as in my imaginary bullfighting cases.

I think public discussion of things like condoms and sex education could be significantly improved if participants in the discussion were all open and clear about the fact that we should expect some degree of risk compensation—that's just decision theory[note 1]—and were mutually clear on what value they ascribe to the sexual activity itself, independently of the risks in question.

In these kinds of cases, it sounds very attractive to say: "Let's focus on what we all agree on. Being gored, getting AIDS and teen pregnancy are worth preventing." But a public policy focused successful at improving the outcomes we have consensus on can still be on balance harmful, as my (made up) bullfighting example shows.

A functional account of marriage vows

What does a couple have to validly promise each other, explicitly or implicitly, in order for those promises, when appropriately ratified by authority, to give rise to a marriage?

This is a hard question as to the specifics. But we can at least give a start of a functional characterization:

• Marriage vows are that complex of binding commitments that in fact makes it prima facie permissible for a couple to engage in intercourse.

One might want to add that the complex is natural, either in the David Lewis sense (in which case it is opposed to gerrymandered) or in the natural law sense (in which case it is that which is consonant with our nature).

Of course, this account can only have plausibility if uncommitted sex is wrong. I think that prior to the 20th century in the West, this functional characterization would have been seen as quite plausible, and I am still inclined to think it is correct.

A functional characterization is not, of course, a definition. Thus someone who disagrees with this characterization can still be talking about the very same thing when using the words "marriage vows" as someone who accepts this characterization.

Risk reduction policies

The following policy pattern is common.  There is a risky behavior which a portion of a target population engages in.  There is no consensus on the benefits of the behavior to the agent, but there is a consensus on one or more risks to the agent.  Two examples:

• Teen sex: Non-marital teen sex, where the risks are non-marital teen pregnancy and STIs.
• Driving: Transportation in motor vehicles that are not mass transit, where the risks are death and serious injury.

In both cases, some of us think that the activity is beneficial when one brackets the risks, while others think the activity is harmful.  But we all agree about the harmfulness of non-marital teen pregnancy, STIs, death and serious injury.

In such cases, it is common for a "risk-reduction" policy to be promoted.  What I shall (stipulatively) mean by that is a policy whose primary aim is to decrease the risk of the behavior to the agent rather than to decrease the incidence of the behavior.  For instance: condoms and sexual education not centered on the promotion of abstinence in the case of teen sex; seat-belts and anti-lock brakes in the case of driving.  I shall assume that it is uncontroversial that the policy does render the behavior less risky.  

One might initially think--and some people indeed do think this--that it is obvious, a no-brainer, that decreasing the risks of the behavior brings benefits.  There are risk-reduction policies that nobody opposes.  For instance, nobody opposes the development of safer brakes for cars.  But other risk-reduction policies, such as the promotion of condoms to teens, are opposed.  And sometimes they make the argument that the risk-reduction policy will promote the behavior in question, and hence it is not clear that the total social risk will decrease.  It is not uncommon for the supporters of the risk-reduction policy to think the policy's opponents "just don't care", are stupid, and/or are motivated by something other than concerns about the uncontroversial social risk (and indeed the last point is often the case).  For instance, when conservatives worry that the availability of contraception might increase teen pregnancy rates, they are thought to be crazy or dishonest.

I will show, however, that sometimes it makes perfect sense to oppose a risk-reduction policy on uncontroversial social-risk principles.  There are, in fact, cases where decreasing the risk involved in the behavior increases total social risk by increasing the incidence.  But there are also cases where decreasing the risk involved in the behavior decreases total social risk.  

On some rough but plausible assumptions, together with the assumption that the target population is decision-theoretic rational and knows the risks, there is a fairly simple rule.  In cases where a majority of the target population is currently engaging in the behavior, risk reduction policies do reduce total social risk.  But in cases where only a minority of the target population is currently engaging in the behavior, moderate reductions in the individual risk of the behavior increase total social risk, though of course great reductions in the individual risk of the behavior decrease total social risk (the limiting case is where one reduces the risk to zero).

Here is how we can see this.  Let r be the individual uncontroversial risk of the behavior.  Basically, r=ph, where p is the probability of the harm and h is the disutility of the harm (or a sum over several harms).  Then the total social risk, where one calculates only the harms to the agents themselves, is T(r)=Nr, where N is the number of agents engaging in the harmful behavior.  A risk reduction policy then decreases r, either by decreasing the probability p or by decreasing the harm h or both.  One might initially think that decreasing r will obviously decrease T(r), since T(r) is proportional to r.  But the problem is that N is also dependent on r: N=N(r).  Moreover, assuming the target population is decision-theoretic rational and assuming that the riskiness is not itself counted as a benefit (both assumptions are in general approximations), N(r) decreases as r increases, since fewer people will judge the behavior worthwhile the more risky it is.  Thus, T(r) is the product of two factors, N(r) and r, where the first factor decreases as r increases and the second factor increases as r increases.  

We can also say something about two boundary cases.  If r=0, then T(r)=0.  So reducing individual risk to zero is always a benefit with respect to total social risk.  Of course any given risk-reduction policy may also have some moral repercussions--but I am bracketing such considerations for the purposes if this analysis.  But here is another point.  Since presumably the perceived benefits of the risky behavior are finite, if we increases r to infinity, eventually the behavior will be so risky that it won't be worth it for anybody, and so N(r) will be zero for large r and hence T(r) will be zero for large r.  So, the total social risk is a function that is always non-negative (r and N(r) are always non-negative), and is zero at both ends.  Since for some values of r, T(r)>0, it follows that there must be ranges of values of r where T(r) decreases as r decreases and risk-reduction policies work, and other ranges of values of r where T(r) increases as r decreases and risk-reduction policies are counterproductive.

To say anything more precise, we need a model of the target population.  Here is my model.  The members of the population targeted by the proposed policy agree on the risks, but assign different expected benefits to the behavior, and these expected benefits do not depend on the risk.  Let b be the expected benefit that a particular member of the target population assigns to the activity.  We may suppose that b has a normal distribution with standard devision s around some mean B.  Then a particular agent engages in the behavior if and only if her value of b exceeds r (I am neglecting the boundary case where b=r, since given a normal distribution of b, this has zero probability).  Thus, N(r) equals the numbers of agents in the population whose values of b exceed r.  Since the values of b are normally distributed with pre-set mean and standard deviation, we can actually calculate N(r).  It equals (N/2)erfc((r-B)/s), where erfc is the complementary error function, and N is the population size.  Thus, N(r)=(rN/2)erfc((r-B)/s).

Let's plug in some numbers and do a graph.  Suppose that the individual expected benefit assigned to the behavior has a mean of 1 and a standard deviation of 1.  In this case, 84% of the target population thinks that when one brackets the uncontroversial risk, the behavior has a benefit, while 16% think that even apart from the risk, the behavior is not worthwhile.  I expect this is not such a bad model of teen attitudes towards sex in a fairly secular society.  Then let's graph T(r) (on the y-axis it's normalized by dividing by the total population count N--so it's the per capita risk in the target population) versus r (on the x-axis). (You can click on the graph to tweak the formula if interested.)

We can see some things from the graph.  Recall that the average benefit assigned to the activity is 1.  Thus, when the individual risk is 1, half of the target population thinks the benefit exceeds the risk and hence engages in the activity.  The graph peaks at r=0.95.  At that point one can check from the formula for N(r) that 53% of the target population will be engaging in the risky activity.

We can see from the graph that when the individual risk is between 0 and 0.95, then decreasing the risk r always decreases the total social risk T(r).  In other words we get the heuristic that when a majority (53% or more for my above numbers) of the members of the population are engaging in the risky behavior, we do not have to worry about increased social risk from a risk-reduction policy, assuming that the target population does not overestimate the effectiveness of the risk-reduction policy (remember that I assumed that the actual risk rate is known).

In particular, in the general American adult population, where most people drive, risk-reduction policies like seat-belts and anti-lock brakes are good.  This fits with common sense.

On the other hand, when the individual risk is between 0.95 and infinity, so that fewer than 53% of the target population is engaging in the risky behavior, a small decrease in the individual risk will increase T(r) by moving one closer to the peak, and hence will be counterproductive.

However, a large enough decrease in the individual risk will still put one on the left side of the peak, and hence could be productive.  But the decrease may have to be quite large.  For instance, suppose that the current individual risk is r=2.  In that case, 16% of the target population is engaging in the behavior (since r=2 is one standard-deviation away from the mean benefit assignment).  The per-capita social risk is then 0.16.  For a risk-reduction policy to be effective, it would then have to reduce the individual risk so that it is far enough to the left of the peak that the per-capita social risk is below 0.16.  Looking at the graph, we can see that this would require moving r from 2 to 0.18 or below.  In other words, we would need a policy that decreases individual risks by a factor of 11.

Thus, we get a heuristic.  For risky behavior that no more than half of the target population engages in, incremental risk-reduction (i.e., a small decrease in risk) increases the total social risk.  For risky behavior that no more than about 16% of the target population engages in, only a risk-reduction method that reduces individual risk by an order of magnitude will be worthwhile.

For comparison, condoms do not offer an 11-fold decrease in pregnancy rates.  The typical condom pregnancy rate in the first year of use is about 15%;  the typical no-contraceptive pregnancy rate is about 85%.  So condoms reduce the individual pregnancy risks only by a factor of about 6.

This has some practical consequences in the teen sex case.  Of unmarried 15-year-old teens, only 13% have had sex.  This means that risk-reduction policies aimed at 15-year-olds are almost certainly going to be counterproductive in respect of reducing risks, unless we have some way of decreasing the risks by a factor of more than 10, which we probably do not.  In that population, the effective thing to do is to focus on decreasing the incidence of the risky behavior rather than decreasing the risks of the behavior.

In higher age groups, the results may be different.  But even there, a one-size-fits-all policy is not optimal.  The sexual activity rates differ from subpopulation to subpopulation.  The effectiveness with regard to the reduction of social risk depends on details about the target population.  This suggests that the implementation of risk-reduction measures might be best assigned to those who know the individuals in question best, such as parents.

In summary, given my model:

• When a majority of the target population engages in the risky behavior, both incremental and significant risk-reduction policies reduce total social risk.
• When a minority of the target population engages in the risky behavior, incremental risk-reduction policies are counterproductive, but sufficiently effective non-incremental risk-reduction policies can be effective.
• When a small minority--less than about 16%--engages in the risky behavior, only a risk-reduction policy that reduces the individual risk by an order of magnitude is going to be effective;  more moderately successful risk-reduction polices are counterproductive.

The concept of marriage

I will give an argument that many people in our society are operating with a concept of marriage that differs in a central way from the traditional Western concept of marriage. I will then say a little on the same-sex marriage debate.

Entry into an institution is largely or wholly defined normatively by what participation in the institution makes permissible, obligatory or impermissible. Some of these normative features of institutions are central to the role that the institution plays and some may not be so central.

In the Western tradition, one of the normative features of the institution of marriage is that it bestows on the couple the permission to engage in sexual relations. Moreover, this normative feature has been quite central to the institution of marriage in the West. For instance, this permission to have sex has very often been one of the main reasons for a couple to marry (St. Paul certainly sees it this way). In fact, of the permissions that the institution of marriage bestows on a couple, it is hard to find any others that are of equal centrality. Marriage bestows a permission to call oneself "married", but that is mainly a word. Most of the other permissions, such as those involving taxation, visitation, living under one roof, etc. are clearly much more contingent in the Western tradition.

But presently, many believe that it can be permissible for unmarried people to have sex. Therefore, entry into marriage is presumably not seen by them as the bestowal of the permission to engage in sexual relations. It is hard to deny that this is a change in a central feature of the concept of marriage. In the past, marriage's normative impact in the sexual sphere of activity was that something previously impermissible—sexual relations—became permissible. Thus, marriage significantly expanded the options for sexual activity. In the present day, marriage's normative impact in the sexual sphere is seen by many as a contraction—rather than allowing previously forbidden sexual activity with a spouse, marriage forbids previously allowed sexual activity with others. This is a very significant change in how marriage works. (I shouldn't say that marriage in the past caused no new prohibitions. For instance, it implied a prohibition against flirting behavior with others than the spouse, etc. But in terms of sexual relations, marriage extended the options.)

I suspect that few advocates of same-sex marriage believe non-marital sex is always wrong. Therefore, they are already operating with a different concept of marriage from the traditional one. Moreover, if one sees marriage sexually as primarily constricting of permissions (prohibiting sex with persons other than the spouse), then it is no surprise that one will have less difficulty with the idea of same-sex marriage—after all, what is wrong, one may ask, with a couple voluntarily constricting what is permissible to them? Expanding what is permissible is a more serious issue.

Thus, I think it is very important that those who believe in the correctness of the traditional Western understanding of marriage not overfocus on the same-sex marriage issue. The issue of fornication—and of divorce for that matter—is probably at least equally important.

Premarital sex and marriage as a social institution

Let us suppose, to see where this false assumption leads us, that premarital sex were morally permissible. Let us also suppose that marriage is a social institution and that a social institution is defined normatively by the duties and permissions one gains as a result of entering into the institution.

Now, all the substantive non-sexual duties and permissions of marriage can be had by a non-marital relationship (I say "substantive", because there is one permission that cannot be had except by those who are married, and that is the permission to say "we are married"). Two people who love each other as brother and sister (in fact, they could actually be brother and sister) could simply come together and through carefully written contracts (against the background of a state that gives sufficient authority to contracts) give each other the duties that marriage involves, and those permissions that depend on one another's agreement, and the state could then do the rest for them.

Thus, marriage, if it an institution, has to bestow sexual duties and/or permissions. Could this just be the duty not to have sex with anybody else? I don't think so. The two people who love each other as brother and sister could promise each other than neither would have sex with anybody, and then they would automatically acquire the duty not to have sex with anybody else (this is a controversial point—I know at least one philosopher who will deny the inference here). Since premarital sex was assumed to be permissible, the couple does not acquire the permission to have sex. So what sexual duty or permission do they acquire?

The only remaining plausible candidate is that each acquires a duty (surely a ceteris paribus one) to have sex with the other. Thus, if the argument works, then if (a) marriage is a social institution in the above sense and (b) premarital sex is permissible, then what defines marriage over and beyond a possible committed loving lifelong non-marital relationship is that by marrying the couple gives each other sexual duties towards each other.

This means that if we see marriage as a social institution, and we accept premarital sex as permissible, we will see marriage as basically a "stern" institution (here I am echoing Newman's idea of conscience as a "stern" voice, i.e., one that speaks only of duty), one defined by the conferral of duties rather than of permissions. On the other hand, if we see premarital sex as impermissible, we will see marriage as in large part a permissive institution, one that confers the permission to have sex.

Presumably seeing marriage as a stern institution is a part of why some people in our culture have a negative attitude towards it.