Became involved in revolutionary activity as a teenager. Member of the SDs from 1894. Emigrated to Germany, 1901.
Joined the Mensheviks after the split in the Social Democratic Party (one of the main opponents of Bolshevism within the Social Democratic Party). Editor of the newspaperGolos Social Demokrata. Member of the Menshevik Central Committee After the February Revolution 1917, member of the Central Executive Committee Supported the Provisional government.
After the October Revolution, worked as a doctor. Continued to appear at party congresses as a representative of Menshevism. Expelled from the USSR by Lenin in 1922, stripped of Soviet citizenship, 1923.
Took part in the founding of the Socialist International, 1923. Edited the magazine Novyi Put'.