INTRODUCTION The present little book is, originally, a part of a larger whole. About 1875, Dr. E. Dühring, _privatdocent_ at Berlin University, suddenly and rather clamorously announced his conversion to Socialism, and presented the German public not only with an elaborate Socialist theory, but also with a complete practical plan for the reorganization of society. As a matter of course, he fell foul of his predecessors; above all, he honored Marx by pouring out upon him the full vials of his wrath. This took place about the time when the two sections of the Socialist party in Germany--Eisenachers and Lassallians--had just effected their fusion, and thus obtained not only an immense increase of strength, but, what was more, the faculty of employing the whole of this strength against the common enemy. The Socialist party in Germany was fast becoming a power. But to make it a power, the first condition was that the newly-conquered unity should not be imperiled. And Dr. Dühring openly proceeded to form around himself a sect, the nucleus of a future separate party. It thus became necessary to take up the gauntlet thrown down to us, and to fight out the struggle whether we liked it or not. This, however, though it might not be an over difficult, was evidently a long-winded, business. As is well known, we Germans are of a terribly ponderous _Gründlichkeit_, radical profundity or profound radicality, whatever you may like to call it. Whenever anyone of us expounds what he considers a new doctrine, he has first to elaborate it into an all-comprising system. He has to prove that both the first principles of logic and the fundamental laws of the universe had existed from all eternity for no other purpose than to ultimately lead to this newly-discovered, crowning theory. And Dr. Dühring, in this respect, was quite up to the national mark. Nothing less than a complete "System of Philosophy," mental, moral, natural, and historical; a complete "System of Political Economy and Socialism"; and, finally, a "Critical History of Political Economy"--three big volumes in octavo, heavy extrinsically and intrinsically, three army-corps of arguments mobilized against all previous philosophers and economists in general, and against Marx in particular--in fact, an attempt at a complete "revolution in science"--these were what I should have to tackle. I had to treat of all and every possible subject, from the concepts of time and space to Bimetallism; from the eternity of matter and motion to the perishable nature of moral ideas; from Darwin's natural selection to the education of youth in a future society. Anyhow, the systematic comprehensiveness of my opponent gave me the opportunity of developing, in opposition to him, and in a more connected form than had previously been done, the views held by Marx and myself on this great variety of subjects. And that was the principal reason which made me undertake this otherwise ungrateful task.