1873:
May to 1883, Engels works on "Dialects of Nature". He gives a dialectical materialist summary of the major achievements in natural science and criticizes metaphysical and idealist views. The book remains unfinished.

End of Oct. to Nov. 20, Engels stays in Engelskirchen in connection with his mother's dead.

Oct. 31, Nov. 2 and 5 1873, "Volksstaadt" prints Engels' articles on Spanish revolution, entitled "Bakuninists at Work".


1873:
Dec., Marx' "Political Indifferentism" and Engels' "On Authority" appear in Italian Yearly "Almanacco Repubblicano". The articles show the harm of anarchists theories to the working-class movement.


1874:
Summer, Engels prepares a third edition of his "Peasant War in Germany". He writes a special addendum to his preface to the second edition, 1870. Later, Lenin describes the ideas in this addendum as instructive for "German working-class movement, which had become strong, practically and politically".

June 1874-April 1875, in a series of articles entitled, "Fluchtlingsliterature", in Volksstaat magazine, Engels analyses the latest developments and trends in European revolutionary movement,


1875:
March 18-28, in a letter to August Bebel, leader of Social-Democratic Workers' Party of Germany, Engels sets forth Marx' and his own stand on the merger of the two workers' organizations in Germany, Social-Democratic Workers' Party (Eisenachers) and General Association of German Workers (Lassalleans). Engels sharply criticizes the draft program, and the system of Lassallean dogmas in contains.

May 5, Marx sends to Germany his critical remarks on the draft program drawn up for the forthcoming unity congress of Eisenachers and Lassalleans in Gotha. Subsequently, the document came to be known as "Critique of Gotha Program" and was first published on Engels' initiative in 1891.

May 22-27, Gotha Unity Congress at which Socialist Workers' Party of Germany was set up.


1876:
May to June 1878, Engels works on "Herr Eugen Duhring's Revolution in Science", subsequently known as "Anti-Duhring", producing a thorough exposition of Marxist theory. Initially, the book was published as a series of articles in "Vorwarts", from January to December 1877, and from May to July 1878. In 1878, it appeared in Leipzig under separate cover.


1877:
Marx writes Chapter X (From Critical History) for part 2 of Engels' "Anti-Duhring". Marx criticizes Duhring's view on the history of political economy.

Mid-June, At the request of Wolhelm Bracke, Engels writes a short biography of Karl Marx for "Volks-Kalender". It was published in 1878.

Vladimir Lenin, 1918
Berlin, 1840