Born in Ushashy, Russian Empire (present day Belarus).
He was a Russian Jewish theoretician, writer and revolutionary. He was a founder of the Socialist Revolutionary Party, one of the foremost socialist parties in the Russian Empire, and an important promoter of Jewish Diaspora nationalism and Yiddishism. He was vice-president of the Czernowitz Yiddish Language Conference in 1908. He inspired the foundation of the territorialist Jewish Socialist Workers Party in the Russian Empire (the Sejmist Movement) in 1904. He emigrated to the U.S.A. at the start of the First World War, where he joined the Zionist-socialist Poale Zion party. In the late 1930s, he was active in the pro-Soviet Yiddisher Kultur Farband and in the Organization for Jewish Colonization in the Soviet Union. He died in Calgary, Canada, while on a conference tour.