From this fact arises a great contradiction with which the history of mankind is filled. On the one hand, we find the tendency to associate and fraternize for the purpose of conquering and adapting the external world to human needs, and for the satisfaction of the human affections; while, on the other hand we see the tendency to divide into as many separate and hostile factions as there are different conditions of life. These factions are determined, for instance, by geographical and ethnological conditions, by differences in economic position, by privileges acquired by some and sought to be secured by others, or by suffering endured, with the ever recurring desire to rebel. The principle of each for himself, that is, of war of all against all, has come in the course of time to complicate, lead astray, and paralyze the war of all combined against nature, for the common advantage of the human race, which could only be completely successful by acting on the principle of all for each, and each for all. Great have been the evils which humanity has suffered by this intermingling of domination and exploitation with human association. But in spite of the atrocious oppression to which the masses submit, of the misery, vice, crime, and degradation which oppression and slavery produce, among the slaves and their masters, and in spite of the hatreds, the exterminating wars, and the antagonisms of artificially created interests, the social instinct has survived and even developed. Co-operation, having been always the necessary condition for successful combat against external nature, has therefore been the permanent cause of men's coming together, and consequently of the development of their sympathetic sentiments. Even the oppression of the masses has itself caused the oppressed to fraternize among themselves. Indeed it has been solely owing to this feeling of solidarity, more or less conscious and more or less widespread among the oppressed, that they have been able to endure the oppression, and that man has resisted the causes of death in his midst. In the present, the immense development of production, the growth of human needs which cannot be satisfied except by the united efforts of a large number of men in all countries, the extended means of communication, habits of travel, science, literature, commerce, even war itself--all these have drawn and are still drawing humanity into a compact body, every section of which, closely knit together, can find its satisfaction and liberty only in the development and health of all other sections composing the whole.