This article concerns a class of experimental manipulations that require people to generate explanations or imagine scenarios. A review of studies using such manipulations indicates that people who explain or imagine a possibility then express greater confidence in the truth of that possibility. It is argued that this effect results from the approach people take in the explanation or imagination task: They temporarily assume that the hypothesis is true and assess how plausibly it can account for the relevant evidence. From this view, any task that requires that a hypothesis be treated as if it were true is sufficient to increase confidence in the truth of that hypothesis. Such tasks cause increased confidence in the hypothesis at the expense of viable alternatives because of changes in problem representation, evidence evaluation, and information search that take place when the hypothesis is temporarily treated as if it were true.