The Doctrine of Fragmented Mind for Solving the Problems of Inconsistency and Closure and its Criticism

The assumption of the unity of mind is the basic foundation for most kinds of epistemic logic, decision theories, and theories of rationality. According to this hypothesis, at any given time t, the two principles of consistency and closure govern the set of beliefs of each person. On the other hand, both at the level of daily life and some kinds of logic as well, these two principles are repeatedly violated. The doctrine of fragmented mind seeks to explain how the mind can reason, judge, and draw conclusions in many cases relying on the two principles while allowing the violation of consistency and closure in some other cases. In this article, after mentioning the motivations of people to accept the hypothesis of unity, the doctrine of fragmented mind is introduced and clarified, and then it is explained how this doctrine can solve the problems of inconsistency and closure for one of the most important theories of content, namely the theory possible worlds. In the end, the doctrine of the fragmented mind is criticized on two levels. In the first level, it is shown that the doctrine of the fragmented mind is not a new idea and so it can be replaced by some known concepts in the epistemology of belief. In the second level, it is argued that some implausible consequences concerning the relationship between epistemology and philosophy of action result from the doctrine of the fragmented mind.