- In Evidence theory, several conditioning rules for updating belief have been proposed, including Dempster's rule of conditioning. The paper views the conditioning rules proposed so far and proposes a new rule of conditioning based on three requirements. Then, it generalizes the rule to be applied to the case where condition is given by an uncertain belief. The paper also discusses a few interpretations of an equation used for evidential reasoning, one of which is interpreted as conditioning with an uncertain condition. Keywords-- Dempster-Shafer theory of evidence, evidence theory, conditioning rule, evidential reasoning, uncertainty.