Some say or imply, contemptuously, that this is a purely descriptive study. But so long as we have found no other method of treating the question, it will always be better than silence. Hitherto, experimentation applied to the feelings has been kept within very narrow limits, and has done scarcely anything beyond corroborating the data furnished by observation. We must therefore modify our point of view and seek elsewhere; anthropology, the history of customs, of arts, religions and sciences, will often be more useful to us than the contributions of physiology. The experiments of the laboratory inspire some with a faith not to be shaken; but the evolution of the feelings in time and space, through centuries and races, is a laboratory, operating, for thousands of years, on millions of men; and its documentary value is a high one. It would be a great loss to psychology if these documents were neglected. Having been long confined to introspective observation, it has deliberately cut itself off from the biological sciences, considering them alien or useless to its work. It would not be desirable to fall into a similar error with regard to the concrete development of human life, and, after mutilating the study from below, to do so from above. If the intellectual life has its roots in biology, it is only in social facts that it can find its full development. A science never gains by excessive restriction of its scope; it is better to err in the opposite direction.[123] ----- Footnote 123: Among the causes which have given some impulse to the psychology of the feelings during the last half of this century, Ladd (_Psychology, Descriptive and Explanatory_, pp. 163, 164) mentions: (1) the theory of evolution, because the affective phenomena are fundamental and permanent, and men differ from one another far less in their appetites, emotions, and passions than in their ideas and thoughts; and because this doctrine affirms that, underlying the highest forms of feeling, there is always some instinctive tendency; and (2) the literary and artistic movement which began with J. J. Rousseau, and asserts itself more and more in the Wagnerian music and the modern novel, and which should invite psychologists to attempt its analysis. It would be well to add the contemporary sociological studies which have shown the important part played by emotional elements, simple or complex, deliberately eliminated by the economists from their theories of social organisation. ----- Since, therefore, we have to pass in review all the forms of feeling, lower and higher, primary and derived, to note the successive moments of their development, and to follow them in their transformations, one question dominates our whole subject: what causes determine the evolution of the feelings?