From the opening lines

The opening lines of The Duchess of Malfi set the tone for the struggle between good and evil that is to follow. Antonio, who we learn later in the scene is, by the Cardinal’s own judgment, too honest to spy on the Duchess, praises the French court for its lack of sycophants and corruption. Then the Cardinal and Bosola enter, and Antonio tells Delio that Bosola “rails at those things”--vices--”which he wants” (1.1.25), so not only is his appearance of virtue false, it is hypocritical and based around self-interest. The audience quickly realizes that these characters are the antithesis of the virtues Antonio praised as reflected in the French court. Further, in his private conversation, we learn immediately that Antonio is an archetypal man of virtue, one who not only lives honestly but esteems it in others. This analysis is validated throughout the play, and makes him something of an anomaly in this twisted court.