Abstract

The theory of personal probability needs to be developed as a logic of credibility in order to provide an adequate basis for the theories of scientific inference and rational decision making. But standard systems of personal probability impose formal structures on probability relationships which are too restrictive to qualify them as logics of credibility. Moreover, some rules for conditional probability have no justification as principles of credibility. A formal system of qualitative probability which is free of these defects and which leads to a presuppositionless representation theorem is sketched.