Not only do Marx and Engels stand out before the reader in clear relief in all their greatness, but the extremely rich theoretical content of Marxism is graphically revealed, because in their letters Marx and Engels return again and again to the most diverse aspects of their doctrine, emphasising and explaining -- at times discussing and debating -- what is newest (in relation to earlier views), most important and most difficult.
pág. 64 diversos aspectos de su doctrina, y subrayan y explican -- a veces discutiendo y tratando de convencerse mutuamente -- lo más nuevo (en relación con las concepciones anteriores), lo más importante y difícil.