There are ever so many ways that a world might be; and one of these many ways is the way that this world is.
-- David Lewis ( 1986, p. 2)
Within a few short years, research on counterfactual thinking has mushroomed, establishing itself as one of the signature domains within social psychology. This sudden popularity is easily understood. Counterfactual thinking is something familiar to nearly everyone. Even if they have not previously heard the term counterfactual, people instantly recognize it, once it has been defined for them, as something with which they are intimately acquainted. Few indeed have never regretted some action or yearned to have avoided some circumstance. But it is the childlike wonder with which we gaze on "what might have been," into realms of possible, alternative worlds, which truly underlies the excitement of counterfactual research. What if Kennedy had survived his assassin's bullets into a second term in the White House? What if the Nazis had triumphed over the Western democracies in the Second World War? What if your parents had never met? There is something at once obsessively compelling and oddly unsettling about confronting the unrealities that might well have been. In intermixing fantasy and free-form creativity with the tangible truths of our lives, such subjunctive suppositions have the potential to inform, enrich, emote, and even entertain us. As Douglas Hofstadter wrote, "Think how immeasurably poorer our mental lives would be if