Scenarios can be viewed as narratives about alternative futures. As such, they are a formalization of something everybody does naturally as they think about the futureimagine what might happen instead of what they expect to happen, and figure out how to make the alternative happen instead, if it is better than what is expected, or how to make sure it does not happen (or what to do if it does happen), if it is worse than what is expected. On the assumption that understanding this natural form of thinking ahead may be useful to those involved in scenario planning, the structure and uses of narrative thought are discussed, particularly in regard to how they result in what are commonly referred to as cognitive biases and to problems of reaching consensus in groups.