1. Introduction. 2. The Origins of Social Democracy Identity, 1789-1875. 3. Between Isolation and Integration, 1871-1918. 4. In Defense of the Republican State, 1918-1933. 5. Social Democracy Under Conditions of Illegality, 1933-1989. 6. From Golden Age to the End of Social Democracy? The FRG, 1945-1998. 7. Conclusion.