People of the Revolution and the USSR

Social Democratic Party of Germany (SPD) Non-Bolshevik socialists 1850–1932 ○ Natural causes

Founder of Marxist revisionism and evolutionary socialism, author of The Preconditions of Socialism

"I have extraordinarily little interest in what is called the 'final goal of Socialism.' This aim, whatever it be, is nothing to me, the movement everything." — Response to critics (1899)

German SPD theorist and politician. Engels's literary executor and editor of Der Sozialdemokrat, Bernstein began as an orthodox Marxist before his 1899 The Preconditions of Socialism challenged Marx's predictions of capitalist collapse, class polarization, and revolutionary necessity. His dictum "the goal is nothing, the movement everything" laid the foundation for social democracy's reformist, parliamentary turn, creating the schism between revolutionary socialism and evolutionary social democracy. He broke with the SPD's pro-war majority to co-found the anti-war USPD during World War I, and spent his final years defending Weimar parliamentary democracy, dying six weeks before Hitler took power.

Independent Social Democratic Party of Germany (USPD) Non-Bolshevik socialists 1854–1938 ○ Natural causes

Chief theoretician of orthodox Marxism in the Second International, founding editor of Die Neue Zeit, editor of Marx's Capital Vol. IV

"Socialism as a means to the emancipation of the proletariat, without democracy, is unthinkable." — The Dictatorship of the Proletariat (1918)

Leading Marxist theoretician of the Second International. He authored the Erfurt Programme, refuted Bernstein's revisionism, and after the Russian Revolution critiqued Bolshevik rule, creating the defining point of divergence between social democracy and Leninism.