## The Relationship Between Knowledge, Belief, and Certainty (1991)

Venue: | Annals of Mathematics and Artificial Intelligence |

Citations: | 19 - 3 self |

### BibTeX

@ARTICLE{Halpern91therelationship,

author = {Joseph Y. Halpern},

title = {The Relationship Between Knowledge, Belief, and Certainty},

journal = {Annals of Mathematics and Artificial Intelligence},

year = {1991},

volume = {4},

pages = {301--322}

}

### Years of Citing Articles

### OpenURL

### Abstract

: We consider the relation between knowledge and certainty, where a fact is known if it is true at all worlds an agent considers possible and is certain if it holds with probability 1. We identify certainty with belief, interpreted probabilistically. We show that if we assume one fixed probability assignment, then the logic KD45, which has been identified as perhaps the most appropriate for belief, provides a complete axiomatization for reasoning about certainty. Just as an agent may believe a fact although ' is false, he may be certain that a fact ' is true although ' is false. However, it is easy to see that an agent can have such false (probabilistic) beliefs only at a set of worlds of probability 0. If we restrict attention to structures where all worlds have positive probability, then S5 provides a complete axiomatization. If we consider a more general setting, where there might be a different probability assignment at each world, then by placing appropriate conditions on the su...