Psychologist, doctor of philosophy, Zionist socio-political activist, pioneer of career counseling in the interwar period.
He began his socio-political activism while still a student. He was a member of the Jewish Socialist Workers' Youth "Młodość" (Youth), and later of Poale Zion-Left. During the war, he was the director of Centos, establishing daycare centers and boarding schools for children in the Warsaw Ghetto. He was one of the founders of the Anti-Fascist Bloc in the Warsaw Ghetto and co-editor of its organ, "Der Ruf" (The Call). He was a member of the presidium of the Jewish National Committee, which he represented to the Polish underground, and as its representative, he joined the presidium of the Council for Aid to Jews "Żegota." After the so-called Great Liquidation Action, he hid on the "Aryan side." During the Warsaw Ghetto Uprising, he signed a telegram to Szmul Zygielbojm, the Bund's representative on the National Council in London. He also authored the ŻKN's one-day publication "Głos z otchłani" (Voice from the Abyss), published in July 1944. He took part in the Warsaw Uprising, including as a member of the Political Council of the People's Army in Żoliborz.
After the war, from 1947, he served as chairman of the Central Committee of Jews in Poland (CKŻP). From 1947, he served as chairman of the United Jewish Socialist Workers' Party "Poale Zion" in Poland. Expelled from the CKŻP in 1949, he emigrated to Israel the following year, where he joined the United Socialist Party of Israel (MAPAM). From 1951, he served as a member of the Knesset. In 1954, he joined the Communist Party of Israel. Author of On the Division and Object of Social Psychology (1932) and memoirs (1978). He died in Tel Aviv in 1978.
