There is another reason, if any need be given why this book should have been translated into English. Marx’s preface to the present work contains the classic formulation of his historico-philosophic theory known as the Materialistic Interpretation of History. This theory, which until recently was entertained almost exclusively by socialist writers and was hardly heard of outside of socialist circles in English speaking countries, is at last receiving not only due recognition but sympathetic appreciation at the hands of men of science.[1] It is rather a significant coincidence that the work which for the first time clearly formulated the law governing social evolution should have seen the light of day in the same year in which Darwin gave to the world his theory of organic evolution. And as the latter had to fight its way to recognition in the teeth of religious prejudices, so has the recognition of the former been retarded by even more powerful social and political prejudices. The Introduction to the Critique of Political Economy which is added as a supplement to this book is for the first time published in book form in any language. It was written by Marx in 1857, but for reasons explained by him in the preface was not published and in fact was never finished by him, since according to his changed plans it would have fitted more into the last volume of Capital which was to contain a history of political economy. The introduction has been published but lately in the form of a magazine article by Karl Kautsky, editor of the Neue Zeit and literary executor of Karl Marx. A few explanations are here in order with reference to the work of translation. No one is more keenly alive to the shortcomings of the English rendering of the original than the translator himself. While fully conscious that the translation might be greatly improved, he has at times deliberately sacrificed literary finish to closeness to the original. It will be found that many passages have been rendered more clear and concise in Capital in which, according to Marx’s own statement in the preface to that work, they were much simplified and popularized. The Hegelian phraseology is more in evidence in the present work rendering translation a more difficult task. Yet for that very reason it seemed particularly desirable to give to English speaking readers as close a version of the original as was possible. In the few cases where certain passages from this work were reproduced by Marx in Capital, the translation of the latter by Moore and Aveling was freely drawn upon with slight modifications here and there.