Given that Don John scarcely troubles to hide his malevolence, that he bears the useful shorthand ‘bastard’ like an accusing finger as part of his name throughout the play and that his first attempt to screw Claudio over at the ball fails, then why do Claudio and Don Pedro believe him so implicitly? One possible answer is generic rather than psychological. The classical New Comedy, associated with Plautus and Terence, on which Shakespeare often bases his own dramas, delivers a stock cast of lovers, wily servants and boastful soldiers.
