 Every proposition \(A\) can be seen as dividing the agent’s knowledge base into three mutually exclusive and jointly exhaustive parts: a part that speaks in favor of \(A\), a part that speaks against \(A\) (i.e., in favor of \(\neg A \)), and a part that speaks neither in favor of nor against \(A\). \(\Bel(A)\) quantifies the part that supports \(A, \Bel( \neg A)\) quantifies the part that supports \(\neg A\), and I\((\{A, \neg A\}) = 1 - \Bel(A) - \Bel(\neg A)\) quantifies the part that supports neither \(A\) nor \(\neg A\).