Ordinary language often treats deference as an all-or-nothing matter; if one defers to another’s judgment (for example, about where to go to dinner), one effectively lets the other party make the decision. Very few of the doctrines identified by federal courts as instances of deference meet this standard. Instead, the term “deference” is applied in a wide range of circumstances involving varying weights, ranging from Skidmore deference, in which the decision-maker must at least take into account the prior decision but need not give it any pre-fixed degree of weight, to rational basis review, in which the prior decision controls unless it is so absurd that no reasonable person could have reached it on any conceivable set of facts. Any inductively derived definition of deference must capture this range. Accordingly, deference is best defined through an inductive methodology such as “The giving by a legal actor of some measure of consideration or weight to the decision of another actor in exercising the deferring actor’s function.” Deference can be mandatory, because it is commanded by positive law, or discretionary, and it can be justified in particular settings for reasons of legitimacy (legitimation deference), accuracy (epistemological deference), cost (economic deference), or communication (signaling deference).