In the last chapter, we saw how democratic revisionism emerged during the late nineteenth century out of frustration with orthodox Marxism's inability to explain or respond to the needs and demands of the day. In particular, we saw that in France, Socialists found it hard to resist reaching out to peasants, defending democracy, and participating in government – all of which challenged the reigning orthodoxy. In Germany, a gap also opened up between the SPD's theory and praxis, but here orthodoxy came under direct theoretical attack by the democratic revisionism of Eduard Bernstein. As one of the keenest contemporary observers of fin-de-siècle socialism noted, revisionism was “presented by Bernstein and demonstrated by” the French:

By the end of the century, in short, orthodoxy faced growing practical and theoretical challenges.

During the first years of the twentieth century, this challenge continued to spread as the reality of European economic and political life caused more and more socialists to question orthodox Marxism. In particular, socialist parties and the Socialist International became consumed by debates about such issues as cooperation with bourgeois parties and non-proletarian social groups, the role of reform work, the value of democracy, and how to deal with the rising tide of nationalism.