Among savages, and no doubt in primitive societies generally, the social reaction against injurious or even unusual acts on the part of individuals is regulated by the binding force of custom. The ruling opinion is the opinion of all, the ruling custom is the duty for all. The dictates of custom, even of ritual and etiquette, are stringent dictates of morality binding upon all, and the breach of any is equivalent to what we should consider a crime. The savage man is held in the path of duty by a much more united force of public opinion than is the civilized man. But, as Westermarck points out, in a suggestive chapter on customs and laws as the expression of moral ideas, "custom never covers the whole field of morality, and the uncovered space grows larger in proportion as the moral consciousness develops.... The rule of custom is the rule of duty at early stages of development. Only progress in culture lessens its sway."[191] As a community increases in size and in cultivation, growing more heterogeneous, it adheres rigidly to fundamental conceptions of right and wrong, but in less fundamental matters its moral ideas become both more subjective and more various. If a man kills another man out of love to that man's wife, all civilized society is of opinion that the homicide is a "crime" to be severely punished; but if the man should make love to the wife without killing the husband, then, although in some savage societies the act would still have been a "crime," in a civilized society it would usually be regarded as more properly a case for civil action, not for criminal action; while should it come to be known that the wife had from the first been in love with the man, and was married by compulsion to a husband who had brutally ill-used her, then a very considerable section of the civilized community would actually transfer their sympathies to the offending couple and look upon the husband as the real offender.