Born April 9, 1872 in Paris to a Jewish middle-class family. In 1894 he graduated from the law faculty of the Sorbonne, earning a doctorate in law. Until 1919 Blum worked as a lawyer. At the same time he engaged in literary activities. Among his works - New conversations of Goethe and Eckermann (Nouvelles Conversations de Goethe avec Eckermann, 1901); About marriage (Du Mariage, 1907), Stendhal and beylizm (Stendhal et le Beylisme, 1914).
Dreyfus led Blum to enter politics. At that time he was under the influence Zh.Zhoresa ideas. In 1902 Blum joined the French Socialist Party and published articles in the newspaper "L`Humanite