The essay which follows had been printed, and was on the point of being published, when the outbreak of war involved my venture in the general devastation from which we are only now emerging. More than four years of military service lie between me and the studies of which this book is the summary. It was written under one dispensation; it is being published under another. My first impulse, therefore, was to ask whether the change which has rendered so much of the old world obsolete had not invalidated also the conclusions here arrived at. But reflection has simply.