The degrees of belief of rational agents should be guided by the evidence available to them. This paper takes as a starting point the view—argued elsewhere—that the formal model best able to capture this idea is one that represents degrees of belief using Dempster–Shafer belief functions. However, degrees of belief should not only respect evidence; they also guide decision and action. Whatever formal model of degrees of belief we adopt, we need a decision theory that works with it: that takes as input degrees of belief so represented. The task of this paper is to develop such a decision theory for the belief function model of degrees of belief. This is not the first paper to attempt that task, but compared to the existing literature it takes a more abstract route to its destination, via a consideration of the very idea of rational decision making in light of one’s beliefs and desires. After presenting the new decision theory and comparing it to existing views, the paper goes on to consider diachronic decision situations.

理性主体的信念程度应以他们可用的证据为指导。本文以一种观点为起点——在别处有争论——最能捕捉这一想法的正式模型是使用 Dempster-Shafer 信念函数表示信念程度的模型。但是，信念的程度不仅应该尊重证据，还应该尊重证据。它们还指导决策和行动。无论我们采用何种正式的信念程度模型，我们都需要一个与其一起工作的决策理论：将如此表示的信念程度作为输入。本文的任务是为信念度的信念函数模型开发这样一个决策理论。这不是第一篇尝试这项任务的论文，但与现有文献相比，它采用更抽象的路线到达目的地，通过考虑根据一个人的信念和愿望做出理性决策的想法。在介绍了新的决策理论并将其与现有观点进行比较后，本文继续考虑历时决策情况。