 Next, each theorist of progress offers a causal story to explain the improvement in the human condition that he thinks has occurred.  The notion of a universal history, a historical narrative taking all of humanity as its subject, came to prominence during the Enlightenment. Universal historians aspired to surpass ordinary historians in breadth and depth and aimed to penetrate the surface play of events to discover fundamental laws of historical development.  These laws would not only explain the past, but could be used to predict the future. Although a universal history need not be an account of improvement, all accounts of progress rest explicitly or implicitly on a universal history. 