A counterfactual conditional abbreviated , is a subjunctive conditional containing an if-clause which is contrary to fact. The term counterfactual was coined by Nelson Goodman in 1947, extending Roderick Chisholm's (1946) notion of a "contrary-to-fact conditional". The study of counterfactual speculation has increasingly engaged the interest of scholars in a wide range of domains such as philosophy, psychology, cognitive psychology, history, political science, economics, social psychology, law, organizational theory, marketing, and epidemiology. In 1748, when defining causation, David Hume referred to a counterfactual case:



The difference between indicative and counterfactual conditionals, in a context of past time reference, is one of emphasis, and can be illustrated with a pair of examples in which the if clause is in the past indicative in the first example but in the pluperfect subjunctive in the second:

• If Oswald did not shoot Kennedy, then someone else did.
• If Oswald had not shot Kennedy, then someone else would have.