Abstract: Scientific socialism and social democracy had the same ideological origin and was at the stage of symbiosis in the 19th century. At the end of the 19th and thebeginning of the 20th centuries, there appeared the split in the united socialistideology and movement, and the confrontation between scientific socialism and social democracy began. Post the cold war, both the socialist trends of thought suffered the shock. And with “the third path” as the sign of reform, the conventional social democracy developed into contemporary social democracy. In dealingwith the western social democratic trend of thought, scientific socialism shouldlearn the lesson of the past and grasp the issue on two different levels, abiding by the ideological principle of being practical and realistic.

Key words: scientific socialism, social democracy, Westernpolitical trend of thought