Simplify the following text for a Grade 10 native English-speaking person.
Original: Leszek KoÅ akowski - ( October 23 1927 â '' July 17 2009 ) was a Polish philosopher , who worked mainly in the history of philosophy , history of political ideas and philosophy of religion , essayist , journalist and novelist .
Simplified: Leszek KoÅ akowski ( ; October 23 , 1927 -- July 17 , 2009 ) was a Polish philosopher and historian of ideas .