The Class Struggle (Erfurt Program) (German: Das Erfurter Programm in seinem grundsätzlichen Theil erläutert von Karl Kautsky) is an 1892 book-length work by Karl Kautsky. It was first published in Stuttgart and was the official commentary of the Social Democratic Party of Germany (SPD) on their brief 1891 Erfurt Program (by Kautsky, party leader August Bebel and Eduard Bernstein). It became and is still considered the seminal (and popular) text for Orthodox Marxism and the Second International. Source: Wikipedia (en)