What is it for history to matter? Stephen Gould argued that unpredictability is part of the answer. For example, the “fact” that repeated replays of the history of life would end differently every time is a sign that history matters to the course of evolution. But there is a problem here: if a particular point in the past leaves open alternative possible futures, then in what sense does that point in the past matter with regard to which of the outcomes occurs? We argue that unpredictability is central to the importance of history. However, it is not the unpredictability of the future, but rather the unpredictability of the past itself that is the key. History matters when a particular future depends on a particular past that was not bound to happen, but did.