The Objects of Credence

Abstract This book brings to light a simple and deep insight with profound theoretical and policy implications for all who use the credence framework. There are concepts which need to be rethought, moves which turn out to be invalid, and principles which need to be rejected or transformed. The central aim is to give those who use the credence framework an awareness of the insight and its wide-reaching implications. The credence framework is used throughout the sciences and social sciences. On this framework, credences (degrees of belief, subjective probabilities, or Bayesian probabilities) are assigned to certain objects—but what objects? I argue that the objects of credence are ‘opaque’ or ‘hyperintensional’: to adapt an example from Gottlob Frege, a person’s credence that Hesperus is bright might be different from their credence that Phosphorus is bright, if that person does not know that Hesperus and Phosphorus are one and the same. We might put the point by saying that our credences are not about objects in themselves, but about objects under designators. This point has far-reaching implications for users of the credence framework. There are implications for principles of rationality, including deference principles and the Principal Principle, and practical implications for decision theory and welfare economics. Furthermore, there are implications for how the framework should be interpreted: this book explores both two-dimensionalism and impossible worlds, and assimilating either into the credence framework brings further significant repercussions.