Ferdinand’s obsession with the Duchess is one of confusion in this play. Seeing the death of the Duchess’s children brings no remorse to Ferdinand. Yet seeing the Duchess barely moving and presumed dead (though she dies later on), he can barely look upon her dead body, saying, “Cover her face. Mine eyes dazzle; she died young” (4.2.262). He then berates Bosola for not defending her from Ferdinand’s orders. What was most peculiar during his berating of Bosola was his explanation of how he wished his sister would not have married and instead her inheritance would be given to him upon her death. My immediate reaction was as if he was trying to excuse himself for feeling such remorse, trying to appear as if he was a tough man who did not care at all for his sister.
Whatever feelings he had for his sister would not be distinguished as family love, but possibly more incestuous in nature. He wants to control her, force her into submission. When he hands her the dagger to push her into killing herself, he wants to have complete control by forcing someone out of their own will into what he wishes them to do (3.2.73). Yet the Duchess is such a strong-minded character that she is able to realize what her brother is attempting to do. After she shows Antonio the dagger, who states matter-of-factly what Ferdinand wishes the Duchess would do with the dagger, she responds, “His action seemed to intend so much” (3.2.154-155). She is clearly aware of her brother’s intentions and may even be hinting towards his obsession over her life (and death). The Duchess is an immensely strong-willed character, while her brother proves himself to be a coward, unable to be fully satisfied with the forces out of his control.
It can be clarifying to propose contemporary psychological diagnoses to explain the behavior of fictional characters, and I think it’s useful to view Ferdinand’s actions as symptoms of obsessive compulsive disorder. His pornographic imagination of the Duchess’s sex life and his use of double-entendres in their conversations provide further clues as to the nature of his compulsions.
I also found it interesting how you diagnosed Ferdinand’s behavior as an anxiety disorder rather than what you would typically expect from a play, a very elaborate and dramatic display of a character. The more I thought about his actions and reasonings throughout the play, there’s evidence that he could be suffering from OCD. The fact that his ‘over protective’ nature contradicts his desire to also kill the Duchess shows his mind’s instability.