Joseph Dietzgen was a German leatherworker and social democrat, who independently developed a number of questions of philosophy and came to conclusions very close to the dialectical materialism of Marx and Engels. After the revolution of 1848 he emigrated to America and in 1864 in search of work, he went to Russia. Working in a tannery in St. Petersburg, Dietzgen devoted all his leisure time to works in the field of philosophy, political economy and socialism. In Russia he wrote a large philosophical treatise, "The Essence of the Mental Labor of Man", a review of the first volume of "Capital" by Karl Marx. In 1869 Dietzgen returned to Germany, and then moved again to America, where he wrote his philosophical works "Excursions of a Socialist in the Field of the Theory of Knowledge" and "Acquisition of Philosophy".