Is Incest Next?


In April, 2003 then Senator Rick Santorum said in an interview, “If the Supreme Court says that you have the right to consensual sex within your home, then you have the right to bigamy, you have the right to polygamy, you have the right to incest, you have the right to adultery.” Gay rights advocate David Smith responded with indignation,”The outrageous thing … is that he put being gay on the same legal and moral plane as a person who commits incest.”[2]    

Ideas have consequences, though they are not the only things that have consequences, and their logical and social consequences are distinct.   The plausibility of a slippery slope argument in one context depends in part how slippery the slope proves elsewhere.  We all have an understanding of the straight and narrow, even those of us who neither believe in it nor practice it. Life-style liberals seek the greatest possible freedom for uncustomary behavior, without going all the way to social chaos; their view inevitably raises the question of limits.  People who depart to some degree from this understanding resent their association with people who go further still.  Those who defend incest between adults, for example, are likely to condemn vehemently incest with children, or incestuous reproduction.[3]      

So far there is no incest liberation movement outside the fringes of the World Wide Web,[4] with the exception of the attempts of ‘kissing cousins’ to gain legitimacy.[5]  Likewise, pedophile liberation has been firmly relegated to the closet.    Yet once inherited prohibitions on sexual behavior are thrown into question, we must face the question, whether this questioning should (or can) stop at the boundaries of the incest prohibition or that of the prohibition on sex with children or at that of sexually charged forms of torture.    There have been significant attempts to bring pedophilia out of the closet.  The poet and homosexual spokesman Allen Ginsberg joined the North American Man Boy Love Association, justifying his action on the unconvincing ground that he was defending their freedom of speech,[6]  and pedophilia continues to have its defenders in the psychological profession.[7]    Hence we cannot take an incest prohibition as an immutable feature of our society, concerning which normative reflection is unnecessary.


Incest is commonly thought to be a universal taboo, but the facts on the ground are complicated.  .  I examine legal, historical, and ethnographical data to discover what ‘we’ think about such issues and each reader should ask him or herself whether these judgments seem sound.  My method will be a form of public phenomenology, suggested by J. L. Austin and the later Wittgenstein, one which asks, not how things appear to me, but how they appear to us – though the deliverances of the ‘wisdom of repugnance’ are always open to correction if sufficiently powerful reasons for changing them are put forward.  There are, I am suggesting certain common human moral responses, though these take different, and sometimes distorted, forms in various cultural settings.

We must distinguish rules about sex from rules about marriage and rules about procreation.  Not only does sex take place outside marriage, and without even possible reproductive consequences; there is reason to suspect that the incestuous marriages of royalty such the Ptolmeys were unconsummated and thus without reproductive consequences.[8]  I here take sex to be the central question in discussions of incest, not marriage or reproduction.   But the availability of artificial insemination and other forms of assisted reproduction means that there can be reproductive incest and reproductive adultery just as much as reproductive rape.

Incest is also tricky because, though the prohibition makes a strong claim to supraconventional validity, the details are a matter of convention.  There may be some relationships – between mother and son, or perhaps even between parents and children – that are incestuous regardless of social practice.  But how we are to know when this sort of thing is the case I do not see.  

At least so far as adult incest is concerned, we must admit an element of convention in any prohibition, and even the age of consent is itself largely conventional. This is by no means a lethal concession:  property is largely a conventional matter, but theft is wrong.  Nor does it mean that supra-conventional principles are not at work in applying these conventions.  St. Thomas Aquinas held that, in situations of extreme need, all goods are in common, though he also held that there are moral prohibitions that hold regardless of consequences or circumstances, including the mores of society.   In contemporary pluralistic societies the answer to the question, what is incest? will vary from subculture to subculture.  

Tell me whether you regard sex between a brother-in law his sister-in-law, between father-in-law and daughter-in-law, between siblings by adoption, between stepsister and stepbrother, between a man and his ex-wife’s mother, or between a man and his former girlfriend’s adopted daughter, is incestuous, and I will tell you how you understand kinship relations.[9]  The same question can be asked of relations between first cousins,[10] between siblings by adoption, or between a brother and a sister raised separately. Relations between stepfather and stepdaughter are certainly incestuous, but there is some doubt about those between stepmother and stepson, though these were strongly prohibited in the ancient world.  A further question is whether marriage matters:  is a woman who seduces her daughter’s boyfriend less bad than one who seduces her daughter’s husband?   There are also some important metaphorical extensions of the idea of incest: the Romans regarded sexual intercourse by a vestal virgin as incestuous (H 82), and the stricter sort of academic feels the same w ay about sex between students and teachers.

Homosexual incest now figures only as “a potent predisposing factor in extreme pathological behavior,”[11] and the lesbian variety in pornography.  Françoise Héritier argues that mother-daughter relations are the most fundamental variety of incest (H 306-07).   At least as extreme a case is sexual relations with one’s identical twin or clone.   Long before this point, sick and creepy have become more appropriate language than morally wrong. I suspect that women the mother-daughter case, and men find the cloning case, creepier.   The one sort of incest implicates the loss self in the devouring Mother, the other the quintessence of narcissism. How masturbation fits into this picture is a question worth asking. 


            There are two broad families of theory of the incest prohibition:  biological and social.  There are legitimate worries about defective offspring arising from frequent mating among close relatives (A chap. 2), and many species of animal avoid inbreeding (A 89-94), but such considerations do not support the conventional prohibition on incest.

The undesirability of inbreeding does not apply to people beyond the age of reproduction, or to those who reliably use contraception or otherwise avoid procreation.  Nor does homosexual incest, or intercourse between stepparent and stepchild, or between relatives by adoption, pose any genetic risk.  Hence we must find the source of the prohibition against incest in the structure of social relations.

            The social theory of incest calls for an answer to a triple0barreled question, why is incest nearly everywhere prohibited, why is this prohibition sometimes violated, and would we better or worse off without it?   Explanatory theories may be relevant to, but do not settle, normative questions.  To be sure there are explanations whose effect is to debunk the prohibition, such as Lord Raglan’s contention that it arose from fear of mysterious origin of having sex with a woman on the same side of the stream as oneself.[12]   The same might seem to be true of Héritier’s contention that incest prohibitions arise from archaic beliefs concerning the circulation of bodily fluids, though bodily fluids might be taken as metaphorical expressions of social or genetic relations (H.188-197, 209-224, and chap.7).     In any event, it is possible that our ancestors had good reasons for their prohibitions.

The ethnologist W. Arens concludes that, while the avoidance of inbreeding is natural, incestuous behavior is the product of culture.   Following Rousseau, he speaks of “an unavoidable conclusion about the human capacity to define and engage in evil” (A 15).   Culture brings with it “hypersexuality, which allows for sex for its own sake or as a medium for conveying other messages about social relations” (A 153). Hypersexuality also leads to forms of sexual behavior which cannot lead to offspring, as well as to ones whose fulfillment in offspring is undesirable.  Also hypersexuality makes possible sexual prohibitions, including prohibitions on forms of incest that cannot produce offspring, or which carry with them no genetic risk. 

Arens’ version of the doctrine of the noble savage, who neither forbids incest nor practices it, is not convincing.  When my neutered male cat attempts futilely to penetrate his spayed sister, he is not attempting incest.  Nor is the prairie vole, which in its natural setting avoids inbreeding (A 93), avoiding incest.  Like theft, adultery, and genocide, incest is a notion that applies only to the behavior of morally accountable entities.  Even in the most custom-ridden society, there is a difference between what is unusual and what is prohibited, and legislators do not bother to prohibit what no one shows any signs of doing.   


Our philosophical, theological, and jurisprudential tradition does not provide a clear answer to the question, what is wrong with incest? or even a clear narrative of progress or decay in our understanding of the prohibition.  Nor does the ethnographic data provide a clear answer. If we construct a narrative of progressive liberation from taboos, we must fact that even the most depraved forms of torture will benefit from it; if we call for a return to the good old days when fundamental taboos were respected, we will end supporting such things as female infanticide.  But the data do supply some reference points for discussion, and some intuitive judgments from which we might extract an account.    For the ‘gut’ reactions of human beings, though fallible, are not totally irrational.

Some ethnologists deny that there is a common essence among the various social phenomena called the incest prohibition.[13]  Among the Mossi of the Upper Volta (now Burkina Faso), incest is regarded as absurd, but without further natural or supernatural consequences; whereas among the Jalé of New Guinea incest is broadly defined and punished by death or by a degrading ordeal (A 6).  In contemporary India, there is no criminal law against incest, but there are honor killings of incestuous spouses (again broadly defined).[14]   In groups that institutionalize homosexuality among unmarried men incest prohibitions paralleling to those which govern heterosexual intercourse and marriage obtain (A 11).  But David M. Schneider reports that “the ideal inseminator is the boy’s father’s sister’s husband” – in other words his uncle, though not by blood (cited in H 235). 

As the title of Arens’ book on incest, Original Sin, indicates, ethnology often borders on theology.   The Hebrew Bible prohibits incest (Leviticus 18:6ff.)   The antinomian tendencies of some passages in the New Testament (Matthew 12:1-6, Mark 2:23-28, Luke 6:1-5, Acts 10:15; 11.9) call the incest  prohibition in question along with Sabbath regulations, dietary laws, other sexual prohibitions, and all other moral rules.  But St. Paul resists such antinomian tendencies — interestingly, the most pertinent case is not blood incest but relations with a stepmother (I Corinthians 5). 

Plato (Republic 461e, Laws 863 a ff.) and Aristotle (Politics Bk. II) take a prohibition on incest for granted on the way to discussing other matters.   Aristotle is troubled by even a chaste romantic relationship between close male relatives (Politics 1262a32ff.),   St, Augustine (City of God Bk. XV, chap. 16)[15] makes five points of continuing relevance.  Incest was necessary when the human race was so few in numbers that the alternative was dying out, but is unacceptable now.  Forms of sexual relationship permitted by law may nonetheless be discouraged by custom.  Out-breeding is desirable because it multiplies relationships of friendship.   In the case of incestuous procreation, “one man would …be both father and father-in-law, and uncle to his own children.” And he appeals to “a natural and praiseworthy shamefacedness which restrains us from desiring that connection … with anyone to whom consanguinity bids us to render respect.”

            I take St. Thomas Aquinas as representing the best reflections of the pre-modern West, and the most serious attempt to synthesize ideas from Greek and from Hebrew sources.   Incest is a problem for him because he does not manifest St. Augustine’s obsessive concern with controlling lust at all costs. And incest is in one sense at least natural in a way homosexual practices or masturbation is not.   For one could not tell, just by looking at a couple, that they were engaging in incest.  And, in the earliest stages of humanity incestuous unions were necessary to the survival of the species. The discussion in the Summa Contra Gentiles (Bk. III, chap. 125) emphasizes marriage rather than sex, although St. Thomas believed that sex outside of marriage was sinful.  Moreover, he allows for dispensation from the incest prohibition both by human and by divine authority (para. 10). So far as I can see, even father-daughter unions might benefit from such dispensations.   

In the Summa Theologiae, St. Thomas adds an intriguing reason: 

Since it is natural that a man should have a liking for a woman of his kindred, if to this be added the love that has its origin in venereal intercourse, his love would be too ardent and would become a very great incentive to lust: and this is contrary to chastity. (IIa IIae Q. 154, art. 9).[16] 

Contemporary moral theologians do little better: Germain Grisez limits himself to saying that “all incest violates family communion.”[17]   Three other Catholic moralists influenced by Grisez add to his account the following questionable sentence:  “Incest is a sin of lust, an act in which pleasure is pursued, with gross disregard for the values toward which of its nature and of divine will sexuality is essentially ordered.”[18]  But incestuous sex can express love, unite the two sexes, and produce offspring.

Kant waffles on the question, whether incest is a crime of the flesh against nature.[19]    Jerome Neu[20]  correctly points to the value of incest taboos.   If a father develops sexual feelings toward his pubescent daughter, he needs not moral reasoning but a stern prohibition to keep his desires in check.  But Neu misses an important feature of kinship relations, and hence also of incest prohibitions:  once a person stands in such a relationship to me, he stands in it forever.  A son estranged from his father is still his father’s son.   If so, though Oedipus may plead ignorance, he is still “objectively” guilty of incest as well as parricide.   Likewise, father-daughter incest remains horrible even if the father is eighty and the daughter twenty.   And, even if we grant that siblings raised apart can couple without incest, siblings raised together are bound by the taboo forever. 

Conventional definitions of incest, and the degree of stigma attached to incestuous behavior, vary widely. Incest remains a felony in almost every State,[21] and its best-known though not necessarily its most frequent form (sex between a father and his underage daughter) is strongly reprobated.   Since this form of incest involves children, it is objectionable on other grounds.   In Rhode Island, though adult incest is not a crime,  incestuous marriages are denied recognition.[22]  This means that incestuous unions are in the same legal boat as homosexual relationships in many jurisdictions, and, as a matter of practice, polygamous relationships in Utah.[23]  They are neither regarded as criminal nor given full legitimation.  .  In Michigan, Rhode Island, and New Jersey, none of which criminalize incest between adults,[24] open incest is not common.  Laws prohibiting marriage between siblings by adoption have been struck down in Colorado.[25]  Recently there was a controversial prosecution of a brother-sister relationship in Germany;[26] the judiciary upheld the law against constitutional challenge.[27]     In practice, incest laws are usually invoked to prosecute incestuous fathers and stepfathers, where the daughter or stepdaughter is below or near the age of consent.[28]   In Florida, the definition of incest is limited to vaginal intercourse, with the result that gay incest is now legal.[29]  While Massachusetts defines incest in ways that include homosexual practices, its definition of consanguinity refers only to opposite sex relationships.[30]   


It is now time to move from a review of the literature to the normative question.  Are prohibitions on incest justifiable, and if so how should we resolve disputed cases?  We begin with the horror that incest evokes in many minds.  It is characteristic of the debate about sexual issues – at least since Lord Devlin’s invocation of “intolerance, indignation and disgust”[31] — that traditional moral views are treated as unreasoned feelings that nonetheless may have some legitimate weight in political and legal reasoning.  Thus Judge Richard Posner, who denies sex any inherent moral meaning, concedes,

If after acquainting himself with all the facts bearing on the sexual perversions, as he may choose to regard them, a person is left with so profound a revulsion that he desires the state to step in and punish the practitioners and is willing to bear his fair share of the public expense of such punishment, I have nothing further to say to him except that he ought to reread chapter 4 of On Liberty.[32]

Incest, however, is not a strictly speaking a perversion and On Liberty is not holy writ.  Nor, I suspect, would even Mill have been prepared positively to evaluate every sexual possibility, if he had had the imagination to envisage them all.

We ought neither disallow our revulsion at incest nor decline to examine it for underlying reasons.  Incest creates discord in the family, and impairs its capacity to form the next generation.  So, however, do domestic violence, quarrels with in-laws, too lax or too rigid discipline, adultery by one or both of the parents, and divorce.   But none of these is subject to as rigid a social prohibition as is incest.  Moreover to some unknown degree the bad effects of incest arise from the prohibition itself.   

We are here moving in a domain where many people’s exercise of moral imagination will be uncomfortable.  Such discomfort tells us something:  a world in which incest (or bestiality or pedophilia) was widely and openly practiced would be a world very different from the present one — one in which the context of our choices, even if we were not ourselves inclined to such practices, would be different from our own, in a perhaps worse way    Such considerations are important, but not decisive.  For people are squeamish about interracial sex and homosexual practices as well as about incest. 

Social, and especially kinship, relations have a grammar, analogous to the grammar of language. We can speak instead of the metaphysics of social relations, provided we do not forget that supraconventional constraints come dressed in conventional garb, that we may not know important natural necessities, and that the very existence of creatures like ourselves is a contingent matter. [33]

Unlike overtly consequentialist or Kantian principles of sexual morality, or applications of general principles forbidding violence and deceit to sexual contexts, that one’s mother or daughter (or father or son) is out of bounds sexually is a grammatical remark.  If an aunt makes advances to her nephew, his spontaneous response is likely to be “But you’re my aunt!”  (Therefore, to spell out the remark more fully, you cannot be my lover.)   We ‘balk’ at expressions in which words fail to fit together appropriately, [34]  and we in similar way balk at certain sexual relationships  In the cases of extreme incest I mentioned earlier, between mother and daughter or parent organism and clone, we encounter the meltdown of the grammar of  both sexual and  social relations.   Though we cannot draw a precise line between nature and convention, at some point our balking represents the recoil of human nature at what violates it.

When human nature is violated, bad consequences are likely to follow.  Thus the existence of bad consequences is evidence of a violation of human nature. There may be consequentialist or other extrinsic reasons for having a social-sexual grammar or for having the particular grammar we have.  Fear of the genetic consequences of inbreeding may make us less accepting of relations between cousins.   But these considerations are effective only to the extent they work through the grammar of kinship relations already in place; one cannot just make up taboos on then ground that they are socially useful.    

In some respects the grammar of familial relations is like the laws of property, or like the allocation of powers among officials in a legal system.  Property relations can be, however, far distant from face-to-face human interactions, as when a corporation owns stock in another corporation (though even such relations sometimes have a powerful impact on the lives of individual human beings).[35]  There are in any case distinctive and powerful emotions associated with violations of the family, commonly expressed in the language of defilement.   In consequence, the grammar of kinship relations is harder to change deliberately than that of property or constitutional structures, though it does, of course change.

Atavistic emotions are not engaged by offenses against property unless they involve such things as the invasion of one’s home.  As for claims of abuse of power by officials, and of their failure to perform their official duties, these are the usual accompaniment of power struggle, and the accompanying emotions are less tangled than those aroused by incest   Nonetheless, the American Constitution has a kind of familial aura associated with the Founding Fathers, and the language of defilement comes into play when it comes to outright bribery.[36].  

The grammar of social relations is transmitted largely through Myths; in the case of incest the most important Myth is that of Oedipus, though that of Hamlet is also pertinent.   (A Myth is not a lie:  it can even be historically accurate, as for example the stories of Paul Revere’s ride and the sinking of Titanic.)  Unfortunately perceptions vary:  some people ‘balk’ at the notion of time travel or same-sex marriage; others do not. Likewise, some people balk the notion of marriage or a sexual relationship with a cousin, and others do not.  Linguistic intuitions and moral intuition, though distinct, are akin, especially when the concept in question, like marriage, is essentially contested.  

It is characteristic of the grammar of kinship that the relations in question do not change. Unmarried lovers can marry; a spouse may die, and a previously adulterous relationship then will cease to be so.  But once near kin, always near kin. One can on the other hand, become near kin, by adoption or by marriage; in this respect kinship relations are like the voting age or the age of eligibility for Social Security.  

Non-contractual relationships such as kinship are required by human vulnerability and the protection of those whose bargaining power is poor, and concern to protect their grammar is a natural consequence.  When the grammar of kinship is disrupted, we experience a form of unease that differs from that produced by other behavior of which we may disapprove.  And when it is disrupted, so are the relations built upon it – not only relations among the persons immediately concerned, but also relations among the other people whose lives are affected  by the disruption of communal relations  entails (this sentence is directed against A 56ff). Usually the bad consequences will be on the surface, but when they are not we also have to consider the welfare of a society that relies on kinship relations to provide its structure I take St. Thomas to be hinting at the need for such a grammar when he speaks of “too ardent” love, and not the silly argument that married siblings might have sex too often.  As I read him, the sort of love appropriate between brother and sister, or between father and daughter, if combined with that between lovers or spouses, should cause us to balk  

The need for a grammar of personal relations is also recognized among groups one might expect to repudiate it:  Ned Rorem remarked of the promiscuous “tribal gay scene” in Fifties Greenwich Village, “There wasn’t sex in the family.”[37]  And age differences continue to provide an important element in the grammar of our personal relations:  my students, to state their views with artificial precision, regard sex over forty as a perversion.  

 One purpose of the grammar of sexual relations is to provide for relationships for which sex is out of the question (to prevent sexual rivalries within the family for example).   Another is the use of sexual bonds to forge alliances among groups – if I am required to marry a woman of another clan, my relatives and hers then become relatives of a sort.  I know of two couples who became friends when their children were courting, and came to fear that the children would break up and damage their parents’ friendship. 

Liberal understandings of harm[38] and privacy are fatally ambiguous.   The concept of a victimless crime is used to defend practices, such as abortion, that harm an entity, though one whose moral status is disputed; and privacy is used to support behavior advertised in the Yellow Pages or proclaimed in the media.  But there are also subtler reasons why these concepts are problematic 

In view of the complex and powerful emotions associated with human sexuality, a society needs relationships from which sex is excluded as much as it needs relationships within which sex is not only permitted but encouraged. Of course, one might regret the intensity of sexual feelings, and wish that human beings could couple, or otherwise discharge excess sexual energy, as easily as hungry people satisfy their desires by a snack. But we are not that sort of being and it is pointless to wish that, and dangerous to act as if, we were.

We have, I am suggesting, a collective interest in the integrity of our kinship system, comparable to our collective interest in the integrity of our currency.  What harms it harms us regardless of anything else.  To understand the nature of this interest, it is best to consider the generation represented by our students, which lacks the experience of an unquestioned normative family, and for this reason finds itself increasingly bewildered in its decisions concerning personal relationships.  To be sure, the 1950’s family was not a haven in a heartless world:  attitudes toward the sexual and other abuse of children within communities have hardened since then.[39]  Nonetheless, there is something of value in a publicly acknowledged norm, even if it continues to be violated in secret. (This proposition is uncontroversial for such things as racial discrimination.)

The threat of social chaos that underlies the argument in this area is never fully realized in practice.  The sexual life of animals is no more chaotic than any other aspect of their lives.  However much ancient Rome may have earned its reputation of “lustful cruelty and cruel lust” (as St. Augustine put it), contrary principles of loyalty, religion, and marriage were never forgotten.    Corresponding to the socially conservative vision of chaos is a radical vision of human relations unmediated, and therefore undistorted, by social roles, including those of marriage and kinship.  Incest, and even sex with children would be legitimate for this vision, but its advocates draw the line at violence and deceit.  But the contention, that one can remove constraints on the sexual instinct without thereby also removing constraints on violence, is both implausible and not supported by experience. In any event, this vision is never realized in practice:  even communes have a structure.     Yet societies do fall apart, and the consequences are not pleasant.  When order is restored, it is likely to be far more brutal than the repression that the rebels rejected.   Weimar Germany led to Nazi Germany.

Many of the arguments advanced for legitimizing homosexual practices extend also to incest and for that matter to pedophilia. Conversely, one reason given by the informants of anthropologists for incest prohibitions — that it is wrong to “put the same on the same” (maxim of the Samo of Burkina Faso (formerly Upper Volta), cited in H chap. 6, esp. p. 203). – applies quite directly to homosexual practices. [40]   And the same is even more so of Héritier’s fuller formulation:  “What is absolutely unthinkable … is the sexual relationship between perfect identicals.  Unthinkable evil, unthinkable ideal” (H 315).

Denying people their preferred form of sexual expression, or requiring them to keep their practices private, is widely resented in contemporary society. And people involved in nonstandard sexual relationships may love one another; parents and children, and other close kin, are expected to do so.    Yet those who have pressed for the normalization of homosexuality and resisted the normalization of incest are not, strictly speaking, inconsistent. They can be proposing a new grammar for sexual relations, one less rooted in biological facts than is the heterosexual norm.  For incest with one’s stepmother is biologically indistinguishable from sex with another woman of the same age.  Moreover, there are reasons for leniency toward homosexuals that do not apply, at least with the same force, to people in love with, or in lust for, a close family member: the incestuous lover can be told that there are lots of other fish in the sea.   Moreover, kinship relations are now more central to many people’s way of life, or at least to their professions, than are the differences between male and female.  Contemporary sensibility even regards mothers and fathers are interchangeable (a couple will announce “we are pregnant” in defiance of the biological facts).    Yet it is impossible to escape the impression that there is something feigned, or even fraudulent, about such professions.

The complex analogies between gender and kinship join with the lessons of experience supporting the conclusion that slippery-slope considerations cannot be laughed away.  When the Supreme Court upheld a right to contraception, it did not seem that the argument would be later extended to abortion let alone to homosexual practices. Though there is no significant incest rights movement at present, this feature of our politics cannot be taken as permanent.  For the rhetorical resources of such a movement are now in place.



In determining the limits of acceptable behavior, and more particularly in applying a concept like incest, both individuals and communities are faced with a line-drawing problem.  Sometimes the line is drawn by the gut feelings of the individuals concerned, sometimes by the mutually reinforcing feelings of the members of the larger society, sometimes by legislation (whether the criminal law or the law of marriage), and sometimes, as in the book of Leviticus, by divine revelation.  Except for revelation, and even there when it is applied to a complicated case, what is called for is the indispensable but ambiguous virtue of prudence. 

The arguments here deployed to support a modest form of social conservatism might end up supporting a more extreme version.  For the differences between the sexes and the races, like relationships of kinship, form part of our social grammar.  And we would or should not tolerate behavior that undermines the currency or the banking system on the ground that it goes on discretely.

Moreover, America before the Civil Rights Movement was not only replete with racial prejudices; it was expressly structured on racial lines. Thus the Movement assaulted not only some particular law or policy, but a complex social system, of which a prohibition on miscegenation (more severe where the white party was a woman) was one crucial part.   So far as persons of color are concerned, while a member of the Nation of Islam, Malcolm X rejected interracial sex in crude terms.[xli]   James Baldwin hated racism, but he also believed that race was so deeply entrenched in our social structure and conceptual scheme that it could not be removed without a metaphysical revolution.  In his own language, he believed that God was white.[xlii]  Interracial sex – and even more so interracial homosex – was for him an act of metaphysical rebellion. [xliii]  In short, the question once put to racial liberals, would you like your sister to marry a Negro?  needed to be faced.  And this question poses the further question, if racial distinctions are not founded in human nature, what social distinctions are.

The argument from social grammar threatens to support an endless series of further exclusions –class barriers and the exclusion of Jews for example.  It also threatens the revival of other ideas generally thought well discarded, such as the double standard of sexual morality and the corresponding doctrine of two kinds of women. Even intellectual questioning of established ways might be thought dangerous.  St. Thomas used the analogy with the currency I have invoked in connection with incest to defend civil penalties for heresy (Summa Theologiae IIa IIae, Q. 11 a. 3).  Social conservatives must face the possibility of a different slippery slope, not a slope into chaos, but into an untenable form of conformism and immobilism.  

Dealing with this possibility requires going beyond mere conservatism to a search for standards founded in human nature.    Whether we should cease to organize our lives around kinship and gender, as we have endeavored to cease to organize it around race, cannot be settled by a short argument.  The core issue is, whether we object to any grammar of personal relations, or only those we have independent reason to believe unjust.  That one social grammar is unjust does not imply that all are, and conversely that we have a need for a social grammar does not imply that just any possible grammar is just.  Thus the appeal to the grammar of personal relations leaves open the question, what forms of society and personal relationship are good for human beings.  Applied to sexual morality, it raises the issue, how important sexuality is in human life and in what way.  At one end we have the recreational view of sex; at the other end the view of Schopenhauer that sex is an unnecessary evil and that the human species should therefore die out.  In between is the quasi-sacramental view of sex implicit in John Paul II’s theology of the body, which affirms the goodness of sex while objecting to practices that entail its banalization.

The culture wars engage the dispute between those who treasure inherited structures for the procreation and nurturing of human life, which at least arose in a religious context; and those who would replace them with state power or free-form human relations.  On the free-form side, even so pious a writer as Eric Gill draws disturbing implications from the beauty of the human body and the goodness of sexuality. He writes of his discovery of his sexuality

I lived henceforth in a strange world of contradiction:  something which was called  filthy which was obviously clean; something was called ridiculous which was obviously solemn and momentous; something was called ugly which was obviously lovely.[xliv]   

In practice this turned out to imply the legitimation of all forms of sexual behavior, including anal intercourse with an underage daughter.[xlv]  

The deepest question is, does human flourishing require some sort of structure independent of our choices, or is it sufficient for us to be free to whatever we choose to be (or feel like being at any given moment), so long as we are not unjust to other people by standards that do not engage controversial ideas about the human good?   In such a context, what a philosopher wants to hold is of crucial importance:  Thomas Nagel, for example, wants atheism to be true.[xlvi]   

Both nature and convention enter into our understanding of incest, as of all other moral issues, and it is impossible to draw a precise line between their contributions.  In practice, people are best advised to follow what the conventions of their group, in the absence of powerful reasons to the contrary.  For they condition both the consequences and the significance our actions.[xlvii]

 [1] I take my title from Brett H. McDonnell, University of Minnesota Law School, Public Law and Legal Theory Research Paper Series, Research Paper No. 03-14,, accessed February 15, 2010.

[2] William Saletan, “Incest Repellent?” Slate, April 23, 2003.  Santorum’s views were seconded by Marvin Olasky, “From Homosexuality to Incest?”, April 24, 2003,, accessed February 23, 2010. Arguments similar to Santorum’s can also be found in Justice Scalia’s dissent in Lawrence v. Texas, 123 S. Ct. 2472, 2495 (2003) and in Justice White’s opinion for the Court in Bowers v. Hardwick, 478 U.S. 186, 195-96 (1986).

[3] See Johann Hari, “Forbidden Love,” Guardian, January 9, 2002, posted at, accessed February 8, 2010.   A Canadian man having an affair with his sister declares, “It’s nothing like some old man who tries to fuck his three-year old, that’s evil and disgusting.  We’re not fucking perverts.”

[4] This fact is crucial to the argument of McDonald, “Incest.”

[5], accessed February 22, 2010.

[7] For a discussion of recent developments in the psychological profession, see Linda Ames Nicolosi, “The Pedophilia Debate Continues –And DSM Is Changed Again,”, updated September 2, 2008, accessed October 8, 2008.  I am indebted to Virginia Cody for pointing out debate among psychologists to me.

[8]W. Arens, The Original Sin (New York:  Oxford Univ. Press, 1986), chap. 7, cited below as A.   

[9] On secondary incest, where no blood tie is present, see Françoise Héritier, Two Sisters and their Mother, trans. Jeanine Herman (New York: Zone,  2002); see especially her discussion of the case of Woody Allen at  pp. 309-311.  Cited below as H.

[10] On this issue, see Joanna Grossman, “Should the Law be Kinder to ‘Kissin’ Cousins’”? (FindLaw, April 8, 2002).

[11] Florence Kaslow et al., “Homosexual Incest,” Psychiatric Quarterly 53, no. 3 (September, 1981):  184-193

[12] Raglan, Jocasta’s Crime (London:  Watts and Company, 1949), cited in A xii, 98.

[13] Rodney Needham, Remarks and Inventions (London:  Tavistock, 1974).

[14]  Another ‘Honour Killing’ in Haryana,” Hindu, July 24, 2009,, accessed February 8, 2010.

[15] Trans. Marcus Dodd et al. (New York:  Modern Library, 1950).

[17] Grisez, The Way of the Lord Jesus, vol. 2 (Quincy, IL:  Franciscan Press, 1993), chap. 9, Q. E, sec. 2, para. f.   

[18] Ronald Lawler, OFM Cap., Joseph Boyle. Jr., and William E. May, Catholic Sexual Ethics (Huntington, IN:  Our Sunday Visitor, 1985), p. 206. 

[19] Kant, Lectures on Ethics, ed. Peter Heath and J. B. Schneewind, trans. Peter Heath (Cambridge:  Cambridge Univ. Press, 2001),  pp. 159-160

[20] Jerome Neu, A Tear is an Intellectual Thing (New York:  Oxford Univ. Press, 2000), chap. 10.

[21] Richard Posner and Katherine B. Silbaugh, A Guide to America’s Sex Laws  (Chicago:  Univ. of Chicago Press, 1996), p. 128

[22] Laws of Rhode Island, secs.15-1-1-4. 

[23] Kristen Scharnberg and Mayna A. Brachear, “Polygamy … Utah’s Open Little Secret,” Chicago Tribune, September 24, 2006.  http://www/

[24] McDonnell “Incest,” p. 16n73.  .

[25] Israel v. Allen, P. 2d 762 (Colo., 1978), cited in McDonald, “Incest,” p. 23n.110. 

[26] Dietmar Hipp, “Dangerous Love: German High Court Takes a Look at Incest,” Der Spiegel, On-Line, March 11, 2008.

[27] Beschluss des Zweiten Senats, Bundesverfassungsgericht, February 27, 2008, 2 BvR 392/07. Bundesverfassungsgericht.mht!, accessed February 9, 2010.

[28] Posner and Silbaugh, Guide, p. 130

[29] Florida Statutes Annotated sec. 826.04.

[30] Massachusetts General Laws, chap. 272 sec. 2; chap. 207, sec. 1 and 2.   

[31] Devlin, The Enforcement of Morals (London:  Oxford Univ. Press, 1965).

[32] Posner, Sex and Reason (Cambridge, MA:  Harvard Univ. Press, 1992), p. 203.   

[33] For an argument that contingent beings are subject to de re necessities, including overflow necessities unknown to us, see James Ross, Thought and World (Notre Dame:  Notre Dame Univ. Press, 2008).

[34]See Paul Ziff,  “About Ungrammaticalness,” Mind 73, no. 209 (April, 1964):  204-15; and A. C. Baier, “Nonsense” Encyclopedia of Philosophy, ed. Paul Edwards (New York: Macmillan, 1967), vol. 5, pp. 520-22.

[35] The connection between Parkhurst and Hubble in Kermit Roosevelt, In the Shadow of the Law (New York:  Picador, 2006), led to the death and grievous injury of a number of people in a chemical fire.

[36] On the religious background of rules against bribery, see John T. Noonan, Jr., Bribes (Berkeley:  Univ. of California Press, 1984).

[37] Quoted in Mel Gussow, Edward Albee: A Singular Journey (New York:  Applause, 2001), pp. 78-79.

[38] For detailed argument concerning harm, see Steven D. Smith, “The Hollowness of the Harm Principle,” Legal Studies Research Paper Series, No. 05-07 (September 2004), available at

[39] On how this happened, see John Pratt, “Child Sexual Abuse:  Purity and Danger in an Age of Anxiety,” Crime, Law, and Social Change 43 (2005):  263-287.

[40] I have not been able to find a specific discussion of Samo attitudes toward homosexuality, but marriage in Burkina Faso is constitutionally defined as heterosexual (Constitution [1997], Tit. 1, chap. 3, art. 23), and a Peace Corps document advises gay, lesbian, and bisexual volunteers in Burkina Faso to stay in the closet.  “Diversity and Cross-Cultural Issues in Burkina Faso,”­_Gay.2C_Lesbian_2C_or_Bisexual_Volunteers,  Accessed March 7, 2011.

[xli]  X, Autobiography, with Alex Halley (New York:  Ballantine, 1965), p. 278.

[xlii] Baldwin, The Fire Next Time (New York:  Dial Press, 1963), pp. 44-45.  .

[xliii] See Baldwin,  Another Country (New York: Dial Press, 1962), esp. pp. 22, 206

[xliv] Quoted in Fiona McCarthy, Eric Gill (London:  Faber and Faber,. 1990), p. 20.  James Hanink suggested Gill’s relevance to my argument.

[xlv] For this incident see ibid., p. 156.

[xlvi]  Nagel, The Last Word (New York:  Oxford Univ. Press, 1996), p. 130.

[xlvii] This essay has benefited from the comments of James Hanink, George Rutherglen, and an anonymous reader, as well as from conversations with Josef Velazquez.


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