Computer Science has had a hard few days:
First Steve Jobs of Apple died
then Dennis Ritchie co-developer of Unix and C dies
and now John McCarthy has died
John was the author of LISP and is credited with coining the concept of Artifiicial Intelligence.
He also turned his attention to a number of other issues
I first came across John when he was nominated for a Distinguished Alumni Award at Caltech, shortly afterwards I moved to NoCal and met John, he was starting thinking long term and I put him in touch with Greg Laughlin who had done some work on a similar project.
I exchanged occasional e-mail with John over the years, and met him for lunch several times when visiting Stanford. He was very sharp and thought about a broad range of issues. He also had the confidence to change his mind when confronted with evidence.
He'll be missed.