Abstract

The aim of the article is to present the idea of common knowledge in the wide range: from intuitions to formal definitions. At the beginning the concept of common knowledge will be exemplified by several anecdotes. Then the hierarchical account (the most popular way of common knowledge formalization) will be presented. The additional advantage of hierarchical account is easiness of its description with use of the notions derived from logic and sciences. Next, Aumann's No Disagreement Theorem is presented. This theorem has greatly contributed to making economists and social researchers interested in common knowledge concept.
At the end of the article several of many applications of common knowledge concept are indicated. Special weight is given to game theory as a primary domain for the concept. The role of common knowledge in the games solutions' seeking techniques is mentioned.

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