Another example may not be amiss. In a general review of moral standards we observe that with increasing civilization a gradual change in the valuation of actions takes place. Among primitive man, human life has little value, and is sacrificed on the slightest provocation. The social group among whose members any altruistic obligations are binding is exceedingly small; and outside of the group any action that may result in personal gain is not only permitted, but even approved; and from this starting-point we find an ever-increasing valuation of human life and an extension of the size of the group among whose members altruistic obligations are binding. The modern relations of nations show that this evolution has not yet reached its final stage. It might seem, therefore, that a study of the social conscience in relation to crimes like murder might be of psychological value, and lead to important results, clearing up the origin of ethical values; but I think here the same objections may be raised as before; namely, the lack of comparable motives. The person who slays an enemy in revenge for wrongs done, a youth who kills his father before he gets decrepit in order to enable him to continue a vigorous life in the world to come, a father who kills his child as a sacrifice for the welfare of his people, act from such entirely different motives, that psychologically a comparison of their activities does not seem permissible. It would seem much more proper to compare the murder of an enemy in revenge with destruction of his property for the same purpose, or to compare the sacrifice of a child on behalf of the tribe with any other action performed on account of strong altruistic motives, than to base our comparison on the common concept of murder (Westermarck). These few data may suffice to show that the same ethnic phenomenon may develop from different sources; and we may infer that the simpler the observed fact, the more likely it is that it may have developed from one source here, from another there. When we base our study on these observations, it appears that serious objections may be made against the assumption of the occurrence of a general sequence of cultural stages among all the races of man; that rather we recognize a peculiar tendency of diverse customs and beliefs to converge towards similar forms. In order to interpret correctly these similarities in form, it is necessary to investigate their historical development; and only when the historical development in different areas is the same, will it be admissible to consider the phenomena in question as equivalent. From this point of view the facts of cultural contact assume a new importance (see p. 166).