The purpose of this paper is to introduce explicitly pleasure and belief in what aims at being a Humean theory of decision, like the one developed in Diaye and Lapidus (2005a). Although we support the idea that Hume was in some way – evidently different from Bentham's or Jevons' way – a hedonist, we lay emphasis less on continuity than on the specific kind of hedonism encountered in Hume's writings (chiefly the Treatise, the second Enquiry, the Dissertation, or some of his Essays). Such hedonism clearly contrasts to its standard modern inheritance, expressed by the relation between preferences and utility. The reason for such a difference with the usual approach lies in the mental process that Hume puts to the fore in order to explain the way pleasure determines desires and volition. Whereas pleasure is primarily, in Hume's words, an impression of sensation, it takes place in the birth of passions as reflecting an idea of pleasure, whose “force and vivacity” is precisely a “belief”, transferred to the direct passions of desire or volition which come immediately before action. As a result, from a Humean point of view, “belief” deals as well with decision under risk or uncertainty, as with intertemporal decision and indiscrimination problems. The latter are explored within a formal framework, and it is shown that the relation of pleasure is transformed by belief into a relation of desire, which belongs to a non-empty class of relations, among which at least one is a preorder.