The origin and development of the moral ideas

Yet it is noteworthy that of all the writers who have discussed it the majority, and certainly not the least able of them, have expressed their belief in marriages between first cousins being more or less unfavourable to the offspring; and no evidence which can stand the test of scientific investigation has hitherto been adduced against this view. Moreover, we have reason to believe that consanguineous marriages are much more injurious in savage regions, where the struggle for existence is often very severe, than they have proved to be in civilised societies, especially as it is among the well-to-do classes that such marriages occur most frequently.

Taking all these facts into consideration, I am inclined to think that consanguineous marriages are in some way or other detrimental to the species. And here I find a quite sufficient explanation of the horror of incest; not because man at an early stage recognised the injurious influence of close intermarriage, but because the law of natural selection must inevitably have operated. Among the ancestors of man, as among other animals, there was no doubt a time, when blood-relationship was no bar to sexual intercourse. But variations, here as elsewhere, would naturally present themselves—we know how extremely liable to variations the sexual instinct is; and those of our ancestors who avoided in-and-in breeding would survive, while the others would gradually decay and ultimately perish. Thus a sentiment would be developed which would be powerful enough, as a rule, to prevent injurious unions. Of course it would display itself, not as an innate aversion to sexual connections with near relatives as such, but as an aversion on the part of individuals to union with others with whom they lived; but these, as a matter of fact, would be blood-relations, so that the result would be the survival of the fittest. Whether man inherited this sentiment from the predecessors from whom he sprang, or whether it was developed after the evolution of distinctly human qualities, we cannot know. It must have arisen at a stage when family ties became comparatively strong, and children remained with their parents until the age of puberty or even longer.

This attempt to explain the prohibition of marriage between kindred and exogamy has not lacked sympathetic support,28 but more commonly, I think, it has been rejected. Yet after a careful consideration of the various objections raised against it I find no reason to alter my opinion. Some of my opponents have evidently failed to grasp the argument on which the theory is based. Thus Professor Robertson Smith argued that it begins by presupposing the very custom which it professes to explain, the custom of exogamy; that “it postulates the existence of groups which through many generations (for the survival of the fittest implies this) avoided wiving within the group.”29 But what my theory postulates is not the existence of exogamous groups, but the spontaneous appearance of individual sentiments of aversion. And if, as Mr. Andrew Lang maintains, my whole argument is a “vicious circle,”30 then the theory of natural selection itself is a vicious circle, since there never could be a selection of qualities that did not exist before.

It has been argued that if close living together calls forth aversion to sexual intercourse, such aversion ought to display itself between husband and wife as well as between near relatives.31 But these cases are certainly not identical. The feeling of which I have spoken is aversion associated with the idea of sexual intercourse between persons who have lived in a long-continued intimate relationship from a period of life when the action of sexual desire is naturally out of the question.32 On the other hand, when a man marries a woman his feeling towards her is of a very different kind, and his love impulse may remain, nay increase, during the conjugal union; though even in this case long living together has undoubtedly a tendency to lead to sexual indifference and sometimes to positive aversion. The opinion that the home is kept free from incestuous intercourse only by law, custom, and education,33 shows lack of discrimination. Law may forbid a son to marry his mother, a brother to marry his sister, but it could not prevent him from desiring such a union. Have the most draconic codes ever been able to suppress, say, homosexual love? As Plato observed, an unwritten law defends as sufficiently as possible parents from incestuous intercourse with their children, brothers from intercourse with their sisters; “nor does the thought of such a thing ever enter at all into the minds of most of them.”34 Considering the extreme variability to which the sexual impulse is subject, it is not astonishing that cases of what we consider incestuous intercourse sometimes do occur.

Dr. Havelock Ellis, again, objects that my theory assumes the existence of a kind of instinct which can with difficulty be accepted. “An innate tendency,” he says, “at once so specific and so merely negative, involving at the same time deliberate intellectual processes, can only with a certain force be introduced into the accepted class of instincts. It is as awkward and artificial an instinct as would be, let us say, an instinct to avoid eating the apples that grew in one’s own orchard. The explanation of the abhorrence of incest is really, however, exceedingly simple…. The normal failure of the pairing instinct to manifest itself in the case of brothers and sisters, or of boys and girls brought up together from infancy, is a merely negative phenomenon due to the inevitable absence under those circumstances of the conditions which evoke the pairing impulse…. Between those who have been brought up together from childhood all the sensory stimuli of vision, hearing, and touch have been dulled by use, trained to the calm level of affection, and deprived of their potency to arouse the erethistic excitement which produces sexual tumescence.”35 I think that Dr. Ellis has considerably exaggerated the difference between my theory and his own. The “instinct” of which I have spoken is simply aversion to sexual intercourse with certain persons, and this is a no more complicated mental phenomenon than, for instance, an animal’s aversion to eating certain kinds of substances. Indeed, Dr.

Ellis himself, in his excellent ‘Studies in the Psychology of Sex,’ gives us many instances not only of sexual indifference, but of sexual aversion, quite instinctive in character.36 Thus the largest proportion of male inverts described by him experience what is called horror feminæ, that is to say, “woman as an object of sexual desire is disgusting” (not merely indifferent) to them.37 And Dr. Ellis also repeatedly speaks of the “abhorrence” of incest.

The objection has been raised that, if my explanation of the prohibition of incest were correct, connections between unrelated persons who have been brought up together should be as repulsive as connections between near kin; whereas, as a matter of fact, the two cases are regarded in a very different light, the latter, only, being held incestuous.38 Much, of course, depends on the closeness of the union, and Dr. Steinmetz’s argument that “the very sensual Frenchmen often seem to marry the lady friends of their earliest youth,”39 is certainly not to the point. I believe that sexual love between a man and his foster-daughter is almost as great an abnormality as sexual love between a father and his daughter; and among some peoples marriages between persons who have been brought up together in the same family or who belong to the same local group, without being related to each other by blood, are held blamable or are actually prohibited.40 Even between lads and girls who have been educated in the same school there is a remarkable absence of erotic feelings, as appears from an interesting communication by a person who has for many years been the head-mistress of such a school in Finland. One youth assured her that neither he nor any of his friends would ever think of marrying a girl who had been their school fellow;41 and I heard of a lad who made a great distinction between girls of his own school and other, “real,” girls, as he called them.

Yet however objectionable and unnatural unions between foster-parents and foster-children or between foster-brothers and foster-sisters may appear to us, I do not deny that unions between the nearest blood-relatives inspire a horror of their own; and it seems natural that they should do so considering that from earliest times the aversion to sexual intercourse between persons living closely together has been expressed in prohibitions against unions between kindred. Such unions have been stigmatised by custom, law, and religion, whilst much less notice has been taken of intercourse between unrelated persons who may occasionally have grown up in the same household. The belief in the supernatural, especially, has played a very important part in the ideas referring to incest, as in other points of sexual morality, owing to the mystery which surrounds everything connected with the function of reproduction.42 The Aleuts in early times believed that incest, which they considered the gravest crime, was always followed by the birth of monsters with walrus tusks, beards, and other disfigurations.43 The Kafirs likewise maintain that the offspring of an incestuous union will be a monster, as “a punishment inflicted by the ancestral spirit.”44 The Bataks of Sumatra regard a long drought as a decisive proof that two cousins have had criminal intercourse with each other.45 The Galelarese think that incest calls forth alarming natural phenomena, such as earthquakes, the eruption of a volcano, or torrents of rain.46 So also the higher religions have branded incest as a heinous sin.

As for Christianity’s views on the subject, it is sufficient to notice that the prohibited degrees were extended by the Church,47 and that the jurisdiction over incest, as over all sexual offences, was exercised by the ecclesiastical courts.48

It has, finally, been argued that my theory utterly fails to explain the fact that prohibitions of intermarriage frequently refer to all the members of a clan, even those who live in different localities.49 In addition to what I have previously observed on this point, I desire to emphasise that every hypothesis pretending to give a full explanation of prohibitions of incest must assume the operation of the very same mental law—that of association—which in my opinion accounts for clan-exogamy. Thus Professor Durkheim, while maintaining that my theory as regards the horror of incest could not apply to exogamy because the members of the same totem do not live together, is himself quite ready to resort to analogy to explain prohibitions extending outside the totem clan. He tries to show that clan-exogamy is the source of all other prohibitions against incest, and that clan-exogamy itself springs from totemism.50 According to him the rule of clan-exogamy has been extended to near relatives belonging to different clans, because they are in no less intimate contact with each other than are the members of the same clan. According to my own theory, again, the prohibition of marriage between near relatives living closely together has been extended to all the members of the clan on account of the notion of intimacy connected with the idea of a common descent and with a common name. If I consider Professor Durkheim’s hypothesis extremely unsatisfactory,51 it is certainly not because he has called in the law of association to explain the rules against incest.

How could anybody deny the operation of this law for instance in the Roman Catholic prohibition of marriage between co-sponsors, or in the rule prevalent in Eastern Europe according to which the groomsman at the wedding is forbidden to intermarry with the family of the bride,52 or in laws prohibiting marriage between relatives by alliance? And why might not the same law be applied to other relationships also, such as those constituted by a common descent or a common name?