Black Swans in negotiation are pieces of information that, once discovered, completely change the entire dynamic and outcome of the negotiation. Chris Voss borrowed the term from Nassim Taleb’s work on unpredictable high-impact events to describe unknown unknowns in negotiation: things you do not know that you do not know, but which, when revealed, transform what is possible. These are not the normal issues you prepare for or the obvious points of leverage. They are hidden motivations, unstated constraints, unknown relationships, or unexpected opportunities that are invisible until discovered but become game-changers once revealed. The concept matters because most negotiation...