Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Leszek Kołakowski October 23, 1927 – July 17, 2009) was a Polish philosopher and historian of ideas. He was best known for his critical analyses of Marxist thought, especially his acclaimed three-volume history, Main Currents of Marxism, which is "considered by some to be one of the most important books on political theory of the 20th century."