Counterfactual history (also virtual history) is a form of historiography that attempts to answer the What if? questions that arise from counterfactual conditions. As a method of intellectual enquiry, counterfactual history explores history and historical incidents by extrapolating a timeline in which key historical events either did not occur or had an outcome different from the actual historical outcome. Counterfactual history seeks by "conjecturing on what did not happen, or what might have happened, in order to understand what did happen." It has produced a literary genre which is variously called alternate history, speculative history, allohistory, and hypothetical history. Development An early book of counterfactual histories is If It Had Happened Otherwise (1931) which features "If Lee Had Not Won the Battle at Gettysburg", by Winston Churchill, about a fictional Confederate victory at the Battle of Gettysburg (1863). As a text of counterfactual histories written by historians, If It Had Happened Otherwise contains works of alternative history—fictional reinterpretations of historical events—because the narrative tone tends to whimsy, and offers neither historical analysis nor the logic behind such What if? scenarios. In Railroads and American Economic Growth: Essays in Econometric History, Robert Fogel applied quantitative methods to imagine the U.S. economy of 1890 had there been no railroads. That in the absence of the railroad in the U.S., the great system of canals would have been expanded and the roads would have been paved and improved into a reliable transport system; both improvements would have diminished the social and economic importance of the railroad, because “the level of per capita income achieved by January 1, 1890 would have been reached by March 31, 1890, if railroads had never been invented.” Few further attempts to bring counterfactual history into the world of academia were made until the 1991 publication of Plausible Worlds: Possibility and Understanding in History and the Social Sciences by the Cambridge sociologist Geoffrey Hawthorn, who carefully explored three different counterfactual scenarios. This work helped inspire Virtual History: Alternatives and Counterfactuals (1997), a collection of essays exploring different scenarios by a number of historians, edited by the historian Niall Ferguson. Ferguson has become a significant advocate of counterfactual history, using counterfactual scenarios to illustrate his objections to deterministic theories of history such as Marxism, and to put forward a case for the importance of contingency in history, theorizing that a few key changes could result in a significantly different modern