He is involved in a long-standing feud with Steven Pinker which basically goes like this:
Pinker: Descriptively, there is less violence in the world today than at any time in recorded human history.
Taleb: How can you claim that we are in a "Long Peace"? There could be a huge terrorist attack tomorrow!
Pinker: I'm not making predictions, I am describing the world as it currently is. The "Long Peace" is a term used by historians to describe post-1945, not a predictive one to describe what will happen in the future.
Taleb: Violence is fat-tailed, nuclear bombs could kill millions of people instantly tomorrow, if you say violence is down you are statistically incompetent. See for example: https://www.facebook.com/13012333374/posts/10151641931853375
According to Taleb, a descriptive book of hundreds of pages of data is insufficient conclusion to say, descriptively, that violence is lower than in the past.