The ideology of democratic confederalism draws heavily on theories of libertarian municipalism, social ecology, and Communalism developed by American anarchist and political philosopher Murray Bookchin, whose works Öcalan read and adapted for the Kurdish movement in the early 2000s while in prison. Öcalan has even described himself as a "student" of Bookchin, and the PKK hailed the American thinker as "one of the greatest social scientists of the 20th century" when he died in 2006.[13]