definition of feeble-mindedness might be modified to meet a varying percentage from age to age should that ever become desirable. (c) AS TO THE NUMBER OF DEFICIENTS NOT DETECTED BY TESTS. If most of the feeble-minded for whom society should provide were of the type which is only conative and not detectable by our present objective tests, a quantitative definition would be abortive. We must, therefore, study our assumption that it is worth while to direct our attention to those who are intellectually deficient. We shall attempt to discover how frequent are the primarily conative types. Before examining the quantitative evidence we may note that it is in conformity with two prominent recent tendencies in psychology to subordinate specialized abilities, as compared with abilities which function commonly in many situations. The first of these tendencies is represented by the fundamental researches of Hart and Spearman (_123_) (_185_). This is not the place to set forth the technical work on which their conclusions are based. It may be said, however, that, with 17 different psychological tests, they were unable to discover any important specific mental weakness which distinguished adults who were suffering with any one of various mental abnormalities, including imbecility, manic-depressive insanity, dementia praecox, paranoia, and general paralysis of the insane. This may have been the fault of the tests, but it seems to be more likely that the fault lies in the custom of emphasizing special abilities and disabilities, at least from the point of view of tested capacities. On the other hand, all of these mental abnormalities showed a weakness in general intellectual ability. This is true whether this general ability be regarded, as it is by Hart and Spearman, as due to a general fund of brain energy, or whether general ability be taken to refer to the common recurrence of many specific abilities in much of our mental life. Its significance for this study is that a series of varied tests, such as that of Binet, may be expected to give a good estimate of general ability, and its failure to disclose specific disabilities is thus less important.