Précis of Rational Powers in Action


  • Sergio Tenenbaum



practical rationality, instrumental rationality, decision theory, extended action, intention


Human actions unfold over time, in pursuit of ends that are not fully specified in advance. Rational Powers in Action locates these features of the human condition at the heart of a new theory of instrumental rationality. Where many theories of rational agency focus on instantaneous choices between sharply defined outcomes, treating the temporally extended and partially open-ended character of action as an afterthought, this book argues that the deep structure of instrumental rationality can only be understood if we see how it governs the pursuit of long-term, indeterminate ends. These are ends that cannot be realized through a single momentary action, and whose content leaves partly open what counts as realizing the end. For example, one cannot simply write a book through an instantaneous choice to do so; over time, one must execute a variety of actions to realize one’s goal of writing a book, where one may do a better or worse job of attaining that goal, and what counts as succeeding at it is not fully determined in advance. Even to explain the rational governance of much less ambitious actions like making dinner, this book argues that we need to focus on temporal duration and the indeterminacy of ends in intentional action. Theories of moment-by-moment preference maximization, or indeed any understanding of instrumental rationality on the basis of momentary mental items, cannot capture the fundamental structure of our instrumentally rational capacities. This book puts forward a theory of instrumental rationality as rationality in action.