_A feeble-minded person is one who is incapable, because of mental defect existing from birth or from an early age, (a) of competing on equal terms with his normal fellows; or (b) of managing himself or his affairs with ordinary prudence._ Two things are to be noted in regard to this definition: In the first place, it is stated in terms of social and industrial efficiency. Such efficiency, however, depends not merely on the degree of intelligence, but also on emotional, moral, physical, and social traits as well. This explains why some individuals with I Q somewhat below 75 can hardly be classed as feeble-minded in the ordinary sense of the term, while others with I Q a little above 75 could hardly be classified in any other group. In the second place, the criterion set up by the definition is not very definite because of the vague meaning of the expression "ordinary prudence." Even the expression "competing on equal terms" cannot be taken literally, else it would include also those who are merely dull. It is the second part of the definition that more nearly expresses the popular criterion, for as long as an individual manages his affairs in such a way as to be self-supporting, and in such a way as to avoid becoming a nuisance or burden to his fellowmen, he escapes the institutions for defectives and may pass for normal. The most serious defect of the definition comes from the lax interpretation of the term "ordinary prudence," etc. The popular standard is so low that hundreds of thousands of high grade defectives escape identification as such. Moreover, there are many grades of severity in social and industrial competition. For example, most of the members of such families as the Jukes, the Nams, the Hill Folk, and the Kallikaks are able to pass as normal in their own crude environment, but when compelled to compete with average American stock their deficiency becomes evident. It is therefore necessary to supplement the social criterion with a more strictly psychological one. For this purpose there is nothing else as significant as the I Q. All who test below 70 I Q by the Stanford revision of the Binet-Simon scale should be considered feeble-minded, and it is an open question whether it would not be justifiable to consider 75 I Q as the lower limit of "normal" intelligence. Certainly a large proportion falling between 70 and 75 can hardly be classed as other than feeble-minded, even according to the social criterion. _Examples of feeble-minded school children_