Common knowledge in legal reasoning about evidence

Douglas Walton, Fabrizio Macagno

Research output: Contribution to journalArticlepeer-review


It is shown how tools of argument analysis currently being developed in artificial intelligence can be applied to legal judgments about evidence based on common knowledge. Chains of reasoning containing generalizations and implicit premises that express common knowledge are modeled using argument diagrams and argumentation schemes. A controversial thesis is argued for. It is the thesis that such premises can best be seen as commitments accepted by parties to a dispute, and thus tentatively accepted, subject to default should new evidence come in that would overturn them. Common knowledge, on this view, is not knowledge, strictly speaking, but a kind of provisional acceptance of a proposition based on its not being disputed, and its being generally accepted as true, but subject to exceptions.

Original languageEnglish
Article number1
Pages (from-to)1-17
Number of pages17
JournalInternational Commentary on Evidence
Issue number1
Publication statusPublished - 2006


  • Crime scene
  • Defeasible reasoning
  • Generalization
  • Presumption
  • Wigmore chart


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