This book has a little history of its own. When a proposal was made to publish the correspondence which had passed between Marx and Engels, Marx's daughter, Madame Laura Lafargue, made it a condition of her agreement that I should take part in the editorial work as her representative. In a letter from Draveil dated the 10th of November 1910 she authorized me to make what notes, explanations or deletions I might consider necessary.
As a matter of fact I made no practical use of this authorization because no important differences of opinion arose between the editors, or rather the editor, Bernstein--Bebel did no more than give his name to the work--and myself, and I had no occasion, no right and naturally no inclination to interfere with his work in the interests of Madame Lafargue without cogent and urgent reasons.
However, during the long work I did in connection with the publication of the correspondence the knowledge which I had gained of Karl Marx during many years of study was rounded off, and involuntarily I felt the wish to give it a biographical frame, particularly as I knew that Madame Lafargue would be delighted at the idea. I won her friendship and her confidence not because she thought me the most learned or the most sagacious amongst the followers of her father, but because she felt that I had obtained the deepest insight into his character and would be able to portray it most clearly. Both in conversation and in her letters she often assured me that many half-forgotten memories of her home life had become fresh and vivid again from the descriptions in my history of the German Social Democracy and in particular in the posthumous edition which I issued, and that many names often heard from her parents developed from a shadowy existence into a tangible reality thanks to my writings.
Unfortunately this noble woman died long before the correspondence between her father and Engels could be published. A few hours before she voluntarily took leave of life she sent me a last, warm message of friendship. She inherited the great qualities of her father, and I thank her beyond the grave for having entrusted me with the publication of many treasures from his literary remains without having made even the slightest attempt to influence my critical judgment in any way. For instance, she gave me the letters of Lassalle to her father, although she knew from my history of the German Social Democracy how energetically and how often I had defended Lassalle against him.
When I finally began to carry out my intention of writing a . . .