1 6 THE AMERICAN JOURNAL OF SOCIOLOGY
The cogency of this rule is due to custom, religion, and law, and is so strong that nearly all Australians would be horrified at the idea of breaking it. If anyone dared to do so, he would probably be clubbed to death.
Here, then, is another restriction to the freedom of marriage which might with equal propriety have been applied to the fur- therance of some forms of eugenics.
5. Taboo. The survival of young animals largely depends on their inherent timidity, their keen sensitiveness to warnings of danger by their parents and others, and their tenacious recol- lection of them. It is so with human children, who are easily terrified by nurses' tales, and thereby receive more or less durable impressions.
A vast complex of motives can be brought to bear upon the naturally susceptible minds of children, and of uneducated adults who are mentally little more than big children. The con- stituents of this complex are not sharply distinguishable, but they form a recognizable whole that has not yet received an appropri- ate name, in which religion, superstition, custom, tradition, law, and authority all have part. This group of motives will for the present purpose be entitled " immaterial," in contrast to material ones. My contention is that the experience of all ages and all nations shows that the immaterial motives are frequently far stronger than the material ones, the relative power of the two being well illustrated by the tyranny of taboo in many instances, called as it is by different names in different places. The facts relating to taboo form a voluminous literature, the full effect of which cannot be conveyed by brief summaries. It shows how, in most parts of the world, acts that are apparently insignificant have been invested with ideal importance, and how the doing of this or that has been followed by outlawry or death, and how the mere terror of having unwittingly broken a taboo may suffice to kill the man who broke it. If non-eugenic unions were pro- hibited by such taboos, none would take place.
6. Prohibited degrees. The institution of marriage, as now sanctified by religion and safeguarded by law in the more highly civilized nations, may not be ideally perfect, nor may it be uni-
