This volume is devoted to the person and work of Leszek Koakowski, who died in July 2009. At the turn of the 1940s and 1950s, Leszek Koakowski belonged to a group of young intellectuals actively supporting on the «ideological front» and in the University of Warsaw the new political agendas of Marxist provenance introduced in Poland. But already in 1955-56, he came to the fore of a movement of philosophical revisionists radically questioning the validity of these Marxist prescriptions. This resulted in his expulsion from the Communist Party in the early 1960s, then from the University and finally from Poland after the «March events» in 1968. Presented in this volume are, on the one hand, texts drawing up a historical balance sheet of theoretical achievements of Leszek Koakowski (articles by Andrzej Walicki and Andrew Targowski), and, on the other, essays devoted to certain aspects of his philosophical position (articles by Marcin Król, Zofia Rosiska, Janusz Dobieszewski, Witold Mackiewicz and Janusz Kuczyski). Also presented in this volume are some occasional essays sketching a portrait of Leszek Koakowski (by Marek J. Siemek, Karol Toeplitz and Jerzy Szacki). The book is closed with an extensive bibliography.