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Classification of the Sci.
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however loose and incongruous it may be. A natural classification, that is to say, a birth-al classification, is a classification whose governing idea coincides with the idea which determines the things classified to exist. An idea, so far as it has any relation to life, is a possible purpose. Therefore the spirit of this work requires us here to regard a natural classification as a classification that conforms to the purpose, or quasi-purpose, of the existence of the objects classified. In case we know what that purpose is, as we should, for example, if we were drawing up a classification of vehicles, it will be a comparatively easy thing,—though none too easy even in that case,—to ascertain approximately the natural classification. Should there be no human purpose, there may, nevertheless, be an evolutionary agency that acts like a purpose, or there may [be] a principle similar to such agency except that it is related, not to a temporal, but to a logical sequence of results. If a natural classi-