We have now acquired the method of studying sociology scientifically so as to attain to assured results. We have acquired it none too soon. The need for a science of life in society is urgent, and it is increasing every year. It is a fact which is generally overlooked that the great advance in the sciences and the arts which has taken place during the last century is producing social consequences and giving rise to social problems. We are accustomed to dwell upon the discoveries of science and the development of the arts as simple incidents, complete in themselves, which offer only grounds for congratulation. But the steps which have been won are by no means simple events. Each one has consequences which reach beyond the domain of physical power into social and moral relations, and these effects are multiplied and reproduced by combination with each other. The great discoveries and inventions redistribute population. They reconstruct industries and force new organization of commerce and finance. They bring new employments into existence and render other employments obsolete, while they change the relative value of many others. They overthrow the old order of society, impoverishing some classes and enriching others. They render old political traditions grotesque and ridiculous, and make old maxims of statecraft null and empty. They give old vices of human nature a chance to parade in new masks, so that it demands new skill to detect the same old foes. They produce a kind of social chaos in which contradictory social and economic phenomena appear side by side to bewilder and deceive the student who is not fully armed to deal with them. New interests are brought into existence, and new faiths, ideas, and hopes, are engendered in the minds of men. Some of these are doubtless good and sound; others are delusive; in every case a competent criticism is of the first necessity. In the upheaval of society which is going on, classes and groups are thrown against each other in such a way as to produce class hatreds and hostilities. As the old national jealousies, which used to be the lines on which war was waged, lose their distinctness, class jealousies threaten to take their place. Political and social events which occur on one side of the globe now affect the interests of population on the other side of the globe. Forces which come into action in one part of human society rest not until they have reached all human society. The brotherhood of man is coming to be a reality of such distinct and positive character that we find it a practical question of the greatest moment what kind of creatures some of these hitherto neglected brethren are. Secondary and remoter effects of industrial changes, which were formerly dissipated and lost in the delay and friction of communication, are now, by our prompt and delicate mechanism of communication, caught up and transmitted through society.