THE LOGIC OF CLASSIFICATION. 239

The point, then, to be insisted on at this stage is, that, in order to a proper grouping, there must be a rational or light-giving principle ; and that wherever you have this, you have to that extent a satisfactory classification, and wherever this is wanting, you have no classification of any scientific value. II. Classification would be a comparatively easy affair, if it demanded nothing more than regard to this simple rule of seeing to it that the grouping is of a light-giving character. Unfortunately, classification is frequently a much more diffi- cult operation than could be satisfied by this simple canon. Not seldom there are competing principles even within the limits of the light-giving ; and these competing principles clash. Where this is so, the rule to be followed is : Arrange the groups so as to bring out the greatest amount of information, having regard to the materials manipulated and the end in view ; in other words, classify upon the greatest number of correlated properties. We may begin with the simple case of the archaeologist and his Relics. Simple as this case is, it shows several com- plications. For, in arranging the relics found in a primitive habitation say a lake-dwelling or a cave the archaeologist has more plans than one open to him ; though, when you consider the nature of his science and his leading -object, there is one that is pre-eminently suitable. He might, for instance, accept the commonly-recognised division of Nature into the three kingdoms of mineral, plant and animal, and arrange his " finds " according as they fall under one group or another. As, however, one of his chief ends is to deter- mine traces of man in the non-historic times, and to ascertain his habits and intelligence, the range of his acquisitions and the stages of his advance in civilisation, he finds that this ground of classification does not throw the full light upon his subject that he would desire, or give him the revelations that it is possible to obtain ; and so, if he be wise, he dis- cards it as a main basis of grouping and has recourse to another which pays regard to the utilities of the objects under consideration. Accordingly, he arranges his relics in two leading divisions viz., (1) relics that have been things of use to man, (2) relics that are simply remains; employing the material of which these relics consist only in his minor sub- divisions. In this way, bones, for instance, whether human or animal, come under the second division, if they are simply remains ; but under the first, if they bear evidence of