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Classification of the Sci
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deutic, the science of the art of discovery, be conducted as a separate science, as occasionally has been done, and not as a secondary branch of logic, as is more usual, it is par excellence the science ministrant to the Gnostic Instinct. As examples of such treatment may be mentioned Jean Senebier's 'L'art d'observer' (Geneva: 1776 2 vols, Ovo) and Catherine Aiken's admirable and remarkable 'Methods of Mind Training (Harpers: 1896).

We have thus passed in review all the sciences of direct gratification. There remain many other practical sciences. Considering how these are, in living fact, affiliated we find that they are of two classes. Namely, some groups of practical sciences each of which is held together by the bond of a common kind of purpose, although this is not itself a gratification of any one instinct. They differ from the sciences of gratification only in the comparatively unimportant circumstance that there is no human instinct immediately motive to that end. Such, for example, is