---
title: "Belief as Defeasible Knowledge"
authors:
  - "Yoav Shoham"
  - "Yoram Moses"
doi: ""
url: "https://ijcai.org/proceedings/1989/187"
pdf: "https://ijcai.org/proceedings/1989/0187.pdf"
venue: "Proceedings of the Eleventh International Joint Conference on Artificial Intelligence"
year: 1989
pages: "1168-1172"
track: "Knowledge Representation"
keywords:
---

# Belief as Defeasible Knowledge

Yoav Shoham, Yoram Moses

*Proceedings of the Eleventh International Joint Conference on Artificial Intelligence*, pages 1168-1172.

## Abstract

We investigate the relation between the notions of knowledge and belief. Contrary to the wellknown slogan about knowledge being ''justified, true belief," we propose that belief be viewed as defeasible knowledge. Specifically, we offer a definition of belief as knowledge-relative-toassumptions , and tie the definition to the notion of nonmonotonicity. Our definition has several advantages. First, it is short . Second, we do not need to add anything to the logic of knowledge: the right properties of belief fall out of the definition and the properties of knowledge. Third , the connection between knowledge and belief is der ived from one fundamental principle, which is more enlightening than a collection of arbitrary-seeming axioms relating the two notions.