Isidor was the son of a merchant, who became a chemist's assistant. In 1898, he started participating in the Group of Workers Revolutionaries. He a later became a member of the Menshevik faction of the RSDLP. He was imprisoned for inciting the Izhorskiye workers to strike. In 1904 he went to Baku, and used the name Theodor Izmaylovich for his political work. By 1906 he was secretary of the newspaper New Life. He then went to Odessa before travelling abroad. In 1907, he returned to Russia, was arrested, again brought to trial but acquitted (1908). He settled in Moscow. After the October Revolution he became a Bolshevik and was appointed finance minister where he advocated for a plan similar to the New Economic Policy, then plenipotentiary representative of Russia in Estonia. He was accused of bribery and corruption during his position as Finance Commissar but died of pneumonia in Estonia before his trial could take place.
