Strictly speaking, we know in advance that it is impossible to set up a limited number of types that would do full justice to the peculiarities of the thousands of languages and dialects spoken on the surface of the earth.  Like all human institutions, speech is too variable and too elusive to be quite safely ticketed.  Even if we operate with a minutely subdivided scale of types, we may be quite certain that many of our languages will need trimming before they fit.  To get them into the scheme at all it will be necessary to overestimate the significance of this or that feature or to ignore, for the time being, certain contradictions in their mechanism.  Does the difficulty of classification prove the uselessness of the task?  I do not think so.  It would be too easy to relieve ourselves of the burden of constructive thinking and to take the standpoint that each language has its unique history, therefore its unique structure.  Such a standpoint expresses only a half truth.  Just as similar social, economic, and religious institutions have grown up in different parts of the world from distinct historical antecedents, so also languages, traveling along different roads, have tended to converge toward similar forms.  Moreover, the historical study of language has proven to us beyond all doubt that a language changes not only gradually but consistently, that it moves unconsciously from one type towards another, and that analogous trends are observable in remote quarters of the globe.  From this it follows that broadly similar morphologies must have been reached by unrelated languages, independently and frequently.  In assuming the existence of comparable types, therefore, we are not gainsaying the individuality of all historical processes; we are merely affirming that back of the face of history are powerful drifts that move language, like other social products, to balanced patterns, in other words, to types.  As linguists we shall be content to realize that there are these types and that certain processes in the life of language tend to modify them.  Why similar types should be formed, just what is the nature of the forces that make them and dissolve them—­these questions are more easily asked than answered.  Perhaps the psychologists of the future will be able to give us the ultimate reasons for the formation of linguistic types.

When it comes to the actual task of classification, we find that we have no easy road to travel.  Various classifications have been suggested, and they all contain elements of value.  Yet none proves satisfactory.  They do not so much enfold the known languages in their embrace as force them down into narrow, straight-backed seats.  The difficulties have been of various kinds.  First and foremost, it has been difficult to choose a point of view.  On what basis shall we classify?  A language shows us so many facets that we may well be puzzled.  And is one point of view sufficient?  Secondly, it is dangerous to generalize from a small number