Desire, belief and expectation

Abstract

Teleology, let us suppose, says that a rational person desires a proposition to a degree equal to that proposition's expected goodness. This is not quite correct,2 but in his paper Desire as Belief (1988), David Lewis takes it for granted, and let us do the same. Suppose there are a number of degrees of goodness, g,, g2, and so on, and let Gj be the proposition that our world is good to degree g, The expected goodness of any proposition A (the expectation of good from A) is