Vladimir Putin killed my friend Alexei Navalny this week. There will be a time and place to discuss the politics and how the free world should respond. For now, I want to share a few memories.

The Alexei Navalny I knew was super smart. For me, the sign of a true intellectual is the courage to change your mind. We disagreed about some things he had said in the past, particularly about the Caucasus and Crimea. He listened...