After finishing elementary school, he worked physically as, among other things, a locksmith, and was involved in workers' movements. From 1896, a member of the Polish Socialist Party. Due to an ongoing investigation, he left for abroad, but returned in 1900, hiding under a false name, actively involved in rebuilding party structures. Arrested twice after the 1900-1901 strike, he was released from prison in 1903. In the following years, he was involved in subversive activities, e.g. as a co-organiser of the peasants' uprising in Łęczyca (1905). In 1914, he joined the Polish Legions and was involved in political and social activities. In 1918, in Daszyński's government, he was Minister for Labour and Social Welfare, and in Moraczewski's government he was Minister for Posts and Telegraphs. Member of the Sejm (1919-1935), Warsaw councillor (1919-1939, with a break from 1935-1937), and member of the PPS Supreme Council. During World War II, he was involved in underground activity. In 1944, he was transferred to London and appointed as successor to Władysław Raczkiewicz, President of the Republic of Poland. Between 1944 and 1947, he was Prime Minister of the Polish Government and Minister of Labour and Social Welfare. He remained politically active until the end of his life.