We still see a lingering theory that war is a result of the ancient migratory or expansion impulse--that over-population and the pressure of various economic conditions are the source of the impulses that lead to war. We have seen reasons for believing, however, that war, even in the beginning, has not been a wholly practical matter. Hunger, pressure of population, migratory movements because of economic conditions, will not explain the origin and the persistence of wars. Wars are not simple as these views would imply, at any stage. That at the present time economic advantage, whether or not it be the motive of war, is in general not gained seems to be very clearly indicated. The taking of colonies and other lands may be a detriment rather than a gain to the conquering nation. The industry and the finance, of all concerned in war, are likely to suffer disaster. Peace is the great producer of wealth. War is a terrible destroyer of it. Ross says that as industry progresses, wars become continually more expensive and less profitable, that the drain is not upon man power so much as upon economic power; nations bleed the treasure of one another until some one of them is exhausted and must yield. The theory that war is caused by the pressure of population, especially as applied to the recent war, now appears to have been very naive. It was maintained that Germany needed more room for her growing population, that Germany must have more land at home and more colonies. Claes (46), among several writers, shows that this is not true. Germany had no pressing need of more land, except for political purposes, or such land as provided the raw materials for her military industries. Bourdon (67) maintains that it is not true that Germany's population was becoming excessive. Le Bon (42) says that this theory of over-population is a myth. Still others have shown that in a country that is rapidly becoming industrial, as was Germany, where population is becoming massed in the great cities, emigration ceases; and that actually, in Germany's case, labor was imported every year, and that there are great tracts of arable land in Germany still but sparsely populated. Nicolai (79) also attacks the theory that war is sought for economic gain and says that an economic war among the European states is an absurdity.