Beyond Belief: Logic in Multiple Attitudes

Choice-theoretic and philosophical accounts of rationality and reasoning address a multi-attitude psychology, including beliefs, desires, intentions, etc. By contrast, logicians traditionally focus on beliefs only. Yet there is logic in multiple attitudes. We propose a generalization of the three standard logical requirements on beliefsconsistency, completeness, and deductive closedness-towards multiple attitudes. How do these three logical requirements relate to rational requirements, e.g., of transitive preferences or non-akratic intentions? We establish a systematic correspondence: each logical requirement (consistency, completeness, or closedness) is equivalent to a class of rational requirements. Loosely speaking, this correspondence connects the logical and rational approaches to psychology. Addressing John Broome's central question, we characterize the extent to which reasoning can help achieve consistent, complete, or closed attitudes, respectively.