He was the only member of the Institute of History of PAN who decided to resign from the membership of the ruling communist party in Poland at that time.
He took part in the discussions at the Crooked Circle Club and was a signatory of the 101 Memorial, an initiative of Polish intellectuals aimed against changes to the Constitution of Poland of 1952.
He collaborated with the Student Committee of Solidarity and participated in the Doświadczenie i Przyszłość ("Experience and Future") discussion group.
He was appointed a member of the supervisory board of the Polish Information Agency and chairman of the "Open Res Publica" Association Against Anti-Seminitsm and Xenophobia.
[8] In 2009, he was awarded (together with Maciej Janowski and Magdalena Micińska) the Jerzy Giedroyc Prize for their collaborative work entitled Dzieje inteligencji polskiej do roku 1918 ("The History of the Polish Intelligentsia until 1918").