Julius caesar act 1 scene 2 what is the effect of cassius question to brutus

Cassius asks Brutus if Brutus can see his own face; Brutus replies that he cannot. Cassius then declares that Brutus is unable to see what everyone else does, namely, that Brutus is widely respected. Noting that no mirror could reveal Brutus's worthiness to himself, Cassius offers to serve as a human mirror so that Brutus may discover himself and conceive of himself in new ways.