White effectiveness is probably due to a superior technique acting in connection with a superior body of knowledge and sentiment. Of two groups having equal mental endowment, one may outstrip the other by the mere dominance of incident. It is a notorious fact that the course of human history has been largely without prevision or direction. Things have drifted and forces have arisen. Under these conditions an unusual incident--the emergence of a great mind or a forcible personality, or the operation of influences as subtle as those which determine fashions in dress--may establish social habits and duties which will give a distinct character to the modes of attention and mental life of the group. The most significant fact for Aryan development is the emergence among the Greeks of a number of eminent men who developed logic, the experimental method, and philosophic interest, and fixed in their group the habit of looking behind the incident for the general law. Mediaeval attention was diverted from these lines by a religious movement, and the race lost for a time the key to progress and got clean away from the Greek copies; but it found them again and took a fresh start with the revival of Greek learning. It is quite possible to make a fetish of classical learning; but Sir Henry Maine's remark, that nothing moves in the modern world that is not Greek in its origin, is quite just. The real variable is the individual, not the race. In the beginning--perhaps as the result of a mutation or series of mutations--a type of brain developed which has remained relatively fixed in all times and among all races. This brain will never have any faculty in addition to what it now possesses, because as a type of structure it is as fixed as the species itself, and is indeed a mark of species. It is not apparent either that we are greatly in need of another faculty, or that we could make use of it even if by a chance mutation it should emerge, since with the power of abstraction we are able to do any class of work we know anything about. Moreover, the brain is less likely to make a leap now than in earlier time, both because the conditions of nature are more fixed or more nearly controlled by man, and hence the urgency of adjustment to sharp variations in external conditions is removed, and because the struggle for existence has been mitigated so that the unfit survive along with the fit. Indeed, the rapid increase in idiocy and insanity shown by statistics indicates that the brain is deteriorating slightly, _on the average_, as compared with earlier times.[269]