Abstract
What theory should we accept from the practical point of view, or accept as a basis for guiding our actions, if we don’t know which theory is true, and if there are too many plausible alternative theories for us to take them all into consideration? This question is the theme of the first three parts of this dissertation. I argue that the problem of theory acceptance, so understood, is a problem of practical rationality, and hence that the appropriate grounds for theory acceptance are practical considerations. I argue for a number of principles of theory acceptance, and I explore the implications of these principles for the acceptance both of descriptive theories and evaluative theories.