It seems hard to maintain that the change in a syntactical construction or in the meaning of a word owes its universality to a simultaneous and independent primary change in all the members of a speech-community. By adopting the theory of imitative spread, all linguistic changes may be viewed as one homogeneous whole. In the second place, the latter view seems to bring linguistic changes into line with the other social changes, such as modifications in institutions, beliefs, and customs. For is it not an essential characteristic of a social group that its members are not co-operative in the sense that each member actively participates in the production of every single element which goes to make up either language, or belief, or customs? Distinguishing thus between _primary_ and _secondary_ changes and between the _origin_ of a change and its _spread_, it behooves us to examine carefully into the causes which make the members of a social unit, either consciously or unconsciously, willing to accept the innovation. What is it that determines acceptance or rejection of a particular change? What limits one change to a small area, while it extends the area of another? Before a final decision can be reached in favor of the second theory of imitative spread it will be necessary to follow out in minute detail the mechanism of this process in a number of concrete instances; in other words to fill out the picture of which Tarde (_Les lois de l'imitation_) sketched the bare outlines. If his assumptions prove true, then we should have here a uniformity resting upon other causes than the physical uniformity that appears in the objects with which the natural sciences deal. It would enable us to establish a second group of uniform phenomena which is psycho-physical in its character and rests upon the basis of social suggestion. The uniformities in speech, belief, and institutions would belong to this second group.[23]