This trait of human thought and speech may be compared in a certain manner to the limitation of the whole series of possible articulating movements by selection of a limited number of habitual movements. If the whole mass of concepts, with all their variants, were expressed in language by entirely heterogeneous and unrelated sound-complexes or word-stems, a condition would arise in which closely related ideas would not show their relationship by the corresponding relationship of their sound-symbols, and an infinitely large number of distinct word-stems would be required for expression. If this were the case, the association between an idea and its representative word-stem would not become sufficiently stable to be reproduced automatically without reflection at any given moment. In the same way as the automatic and rapid use of articulations has brought it about that a limited number of articulations only, each with limited variability, and a limited number of sound-clusters, have been selected from the infinitely large range of possible articulations and clusters of articulations, so the infinitely large number of ideas have been reduced by classification to a lesser number, which by constant use have established firm associations, and which can be used automatically. It seems important at this point of our considerations to emphasize the fact that the groups of ideas expressed by specific word-stems show very material differences in different languages, and do not conform by any means to the same principles of classification. To take the example of English, we find that the idea of “water” is expressed in a great variety of forms: one term serves to express water as a liquid; another one, water in the form of a large expanse (lake); others, water as running in a large body or in a small body (river and brook); still other terms express water in the form of rain, dew, wave, and foam. It is perfectly conceivable that this variety of ideas, each of which is expressed by a single independent term in English, might be expressed in other languages by derivations from the same term. Another example of the same kind, the words for “snow” in Eskimo, may be given. Here we find one word expressing “snow on the ground;” another one, “falling snow;” a third one, “drifting snow;” a fourth one, “a snowdrift.” In the same language the seal in different conditions is expressed by a variety of terms. One word is the general term for “seal;” another one signifies the “seal basking in the sun;” a third one, a “seal floating on a piece of ice;” not to mention the many names for the seals of different ages and for male and female.