civilization is shown by the close association between civilization and mental instability. There is no lack, therefore, of the mental quality of all others most necessary to the gregarious animal. The pressing problem which in fact faces man in the immediate future is how to readjust the mental environment in such a way that sensitiveness may develop and confer on man the enormous advantages which it holds for him, without being transformed from a blessing into the curse and menace of instability. To the biologist it is quite clear that this can be effected only by an extension of the rational method to the whole field of experience, a {65} process of the greatest difficulty, but one which must be the next great variation in man’s development if that development is to continue to be an evolution.
Outside this possibility the imagination can see nothing but grounds for pessimism. It needs but little effort of foresight to realize that without some totally revolutionary change in man’s attitude towards the mind, even his very tenure of the earth may come to be threatened. Recent developments in the study of disease have shown us how blind and fumbling have been our efforts against the attacks of our immemorial enemies the unicellular organisms. When we remember their