 For those who think that the only way to determine a person’s comparative beliefs is to look at her preferences, the lack of uniqueness in Jeffrey’s theory is a big problem. Indeed, this may be one of the main reasons why economists have largely ignored Jeffrey’s theory. Economists have traditionally been skeptical of any talk of a person’s desires and beliefs that goes beyond what can be established by examining the person’s preferences, which they take to be the only attitude that is directly revealed by a person’s behaviour. For these economists, it is therefore unwelcome news if we cannot even in principle determine the comparative beliefs of a rational person by looking at her preferences.