This paper proposes that grammaticized evidential morphemes do not simply encode evidence type (as it has been stipulated so far); rather, they encode relations among three situations: the situation of which a proposition is true, a Reference Situation and the Discourse Situation. Evidentials encode the same relations as do Tense and Aspect morphemes, but they relate situations rather than times. Thus, “evidence” is not a primitive but a relation between the situation S about which one makes an assertion and a situation that either contains or is accessible to S. The restrictions on evidence type are predicted by the fact that containment and accessibility are the only possible relations. The common homophony between Evidential morphemes and Tense/Aspect morphemes is explained because the systems encode the same relations. These parallels motivate the suggestion that all Functional heads encode basically the same relations, which may be seen as fundamentally configurational.