From 1892 onwards he was in contact with Achad Ha'am, one of the founders of the Lovers of Zion (Hovevei Tsyion) movement. In the spring of 1894 he published "Anti-semitism, its History and Causes" ("L'Antisémitisme, son histoire et ses causes"), an in-depth study and critique of the origins of antisemitism. It was published within a few months of the arrest of Captain Alfred Dreyfus, a Jewish army officer accused of treason. Having a reputation for combativeness and courage, Bernard Lazare was contacted by Mathieu Dreyfus to help prove his brother's innocence.