The inside view and the outside view are two alternative approaches to forecasting. Whereas the inside view attempts to make predictions based on an understanding of the details of a problem, the outside view—also called reference class forecasting—instead looks at similar past situations and predicts based on those outcomes. For example, in trying to predict the time it will take a team to design an academic curriculum, a forecaster can either look at the characteristics of the curriculum to be designed and of the curriculum designers (inside view) or consider the time it has taken past teams to design similar curricula (outside view).^[1]

Terminology

The terms "inside view" and "outside view" are sometimes used to refer to other contrasts. First, the terms are used to contrast the views reached exclusively via individual reasoning and the views that also take into account the fact that other reasoners have reached different views. Second, the terms are used to contrast the perspective of someone looking at the problem "from the inside", or first-person perspective, and the perspective of someone looking at the problem "from the outside", or third-person perspective. For example,  Scott Alexander asks whether "it’s better to model [depressed patients'] behavior as based on mysterious brain chemicals rather than on rational choice", and answers that "[i]t would be really weird if depression were the one area where we could always count on the inside view not to lead us astray."^[2]

Noting that the terms are used in these and other related senses, some have proposed that they should be avoided altogether, and replaced by less ambiguous alternatives.^[3]