 According to van Fraassen, explanations are answers to questions and getting clear about the logic of questions is central to constructing a theory of explanation. Questions can take many different forms, but when the question of interest is a “why” question, explanatory queries will typically take the following form: a query about why some explanandum \(P_k\) rather than any one of the members of a contrast class \(X\) (a set of possible alternatives to \(P_k\)) obtained. In addition, some “relevance relation” \(R\) is assumed by the question. An answer \(A\) to this question will take the form “\(P_k\) in contrast to (the rest of) \(X\) because \(A\), where \(A\) bears the relevance relation \(R\) to \([P_k,X]\)”. To use van Fraassen’s example, consider “Why is this conductor warped?” Depending on the context, the intended contrast might have to with, e.g., why this particular conductor is warped in contrast to some other conductor that is unwarped. Alternatively, it might have to do with why this particular conductor is warped now when it was previously unwarped. The relevance relation \(R\) similarly depends on the context and the information which the questioner is interested in obtaining. For example, \(R\) might involve causal information (the question might be a request for what caused the warping) but it also might have to do with information about function, if the context was one in which it is assumed that the shape of the conductor plays some functional role in a power station which the questioner wants to know about. Thus “context” enters into the explanation both by playing a role in specifying the contrast class \(X\) and the relevance relation \(R\). van Fraassen describes various rules for the “evaluation” of answers. For example, \(P_k\) and \(A\) must be true, the other members of the contrast class must not be true, \(A\) must “favor” (raise the conditional probability of) \(P_k\) against alternatives, and \(A\) must compare favorably with other answers to the same question, a condition which itself has several aspects including, for example, whether \(A\) favors the topic more than these other answers and whether \(A\) is screened off by other answers. However, he also makes it clear (as the example above suggests) that a variety of different relevance relations may be appropriate depending on context and that the evaluation of answers also depends on context. Moreover, he explicitly denies that there is anything distinctive about the category of scientific explanation that has to do with its structure or form—instead, a scientific explanation is simply an explanation that makes use of information that is (or at least, is treated as) grounded in a “scientific” theory.