The operation of material conditions may be illustrated by the statement (Myers's _Dawn of History_) that four of the greatest movements of conquest have been due to drought in Arabia, causing the nomads of that country to migrate into regions already inhabited. The last of these four movements was the rise of Islam. In these four cases, the primal need of food and drink was enough to set events in motion; but as this need could only be satisfied by conquest, the four secondary passions must have very soon come into play. In the conquests of modern industrialism, the secondary passions have been almost wholly dominant, since those who directed them had no need to fear hunger or thirst. It is the potency of vanity and love of power that gives hope for the industrial future of Soviet Russia, since it enables the Communist State to enlist in its service men whose abilities might give them vast wealth in a capitalistic society. Intelligence modifies profoundly the operation of material conditions. When America was first discovered, men only desired gold and silver; consequently the portions first settled were not those that are now most profitable. The Bessemer process created the German iron and steel industry; inventions requiring oil have created a demand for that commodity which is one of the chief influences in international politics. The intelligence which has this profound effect on politics is not political, but scientific and technical: it is the kind of intelligence which discovers how to make nature minister to human passions. Tungsten had no value until it was found to be useful in the manufacture of shells and electric light, but now people will, if necessary, kill each other in order to acquire tungsten. Scientific intelligence is the cause of this change. The progress or retrogression of the world depends, broadly speaking, upon the balance between acquisitiveness and rivalry. The former makes for progress, the latter for retrogression. When intelligence provides improved methods of production, these may be employed to increase the general share of goods, or to set apart more of the labour power of the community for the business of killing its rivals. Until 1914, acquisitiveness had prevailed, on the whole, since the fall of Napoleon; the past six years have seen a prevalence of the instinct of rivalry. Scientific intelligence makes it possible to indulge this instinct more fully than is possible for primitive peoples, since it sets free more men from the labour of producing necessaries. It is possible that scientific intelligence may, in time, reach the point when it will enable rivalry to exterminate the human race. This is the most hopeful method of bringing about an end of war.