In the previous act, Ferdinand and the Cardinal both were adamant about not wanting the Duchess to remarry. However, Ferdinand’s refusal is especially evident during Act II scene v, after reading the letter that the Duchess had given birth. Although the Cardinal and Ferdinand are angry upon hearing the news about the Duchess’ birth, when juxtaposed together, their reactions reveal insight into both of these characters. Both characters uses blood in their speech, the Cardinal indicates that the blood in the family is now tainted (2.5.21-22). However, Ferdinand emphasizes that the Duchess deserves to die in which one should “purge infect blood” (2.5.26) Ferdinand continues this in line 49 when he refers to the Duchess’ as “whore’s blood.” Ferdinand extreme reaction is revealing of his character as only he believes that the Duchess should be killed for her (whorish) ways, whereas the Cardinal is almost calm in comparison to Ferdinand.
Ferdinand’s obsession and extreme nature is further revealed as the Cardinal even asks Ferdinand if he has gone “stark mad” (2.5.68). It is ironic that Ferdinand continuously wants to punish the Duchess for her act; however, once the Duchess has been “punished” for her act, Ferdinand shows signs of repent and subsequently does go mad as the play progresses. Therefore, the character of Ferdinand is intriguing because he is a character that likes to pushes actions to the extreme, both mentally and physically.
Ferdinand’s regret and subsequent madness add to the psychological complexity of this play. You’re right, Wendy, to show how different he is from the Cardinal, whose corruption is routine next to the operatic extravagance of Ferdinand’s behavior. It’s not surprising that Richard Burbage, the first Hamlet, Macbeth, and Lear, should have played Ferdinand in The Duchess of Malfi.