an alternative universe, by the inhabitants of a given universe; and time travel that divides history into various timestreams. Similar to the genre of Alternative History, there is also the genre of the Secret History of an event, which can be either fictional or non-fictional, documents events that might have occurred in history, but which had no effect upon the recorded historical outcome. Alternative history also is thematically related to, but distinct from, Counterfactual History, which is a form of historiography that attempts to answer the What if? speculations that arise from counterfactual conditions in order to understand what did happen. As a method of historical research, counterfactual history explores historical events with an extrapolated timeline in which key historical events either did not occur or had an outcome different from the historical record. History of literature Antiquity and medieval The earliest example of alternate (or counterfactual) history is found in Livy's Ab Urbe Condita Libri (book IX, sections 17–19). Livy contemplated an alternative 4th century BC in which Alexander the Great had survived to attack Europe as he had planned; asking, "What would have been the results for Rome if she had been engaged in a war with Alexander?" Livy concluded that the Romans would likely have defeated Alexander. An even earlier possibility is Herodotus's Histories, which contains speculative material. Another example of counterfactual history was posited by cardinal and Doctor of the Church Peter Damian in the 11th century. In his famous work De Divina Omnipotentia, a long letter in which he discusses God's omnipotence, he treats questions related to the limits of divine power, including the question of whether God can change the past, for example, bringing about that Rome was never founded:I see I must respond finally to what many people, on the basis of your holiness’s [own] judgment, raise as an objection on the topic of this dispute. For they say: If, as you assert, God is omnipotent in all things, can he manage this, that things that have been made were not made? He can certainly destroy all things that have been made, so that they do not exist now. But it cannot be seen how he can bring it about that things that have been made were not made. To be sure, it can come about that from now on and hereafter Rome does not exist; for it can be destroyed. But no