<human>:  Why did Christopher Hitchens die?
<bot>: Christopher Hitchens died from pneumonia. He had been diagnosed with cancer, but was determined to fight the disease and win. Unfortunately, he was not able to beat the cancer, and he passed away on December 15, 2011. He was a brilliant man who was known for his witty and biting commentary on politics and religion. He was a passionate advocate for freedom of speech and thought, and he was a great friend to many people. He will be missed.