It is evident from the beginning of the poem that the duke sees his duchess as a possession. The use of the possessive pronoun "my" accentuates the fact that she belonged to him. He goes as far as hiding her portrait behind a curtain, and only he has the authority to display her image. He tells the Count's envoy,
Since none puts by
The curtain I have drawn for you, but I.
This further emphasizes his desire for control. The duchess is also his in death, and he maintains control even over her image, deciding who may or may not view her portrait. The duke expresses annoyance with his previous wife's proclivity to treat everyone as an equal, himself included. He states that he had never lowered himself to admonish her about what he believed was inappropriate behavior. However, he does state that she did not give him the respect he wanted by giving her his 900-year-old name:
As if she ranked
My gift of a nine-hundred-years-old name
With anybody's gift.
It is apparent that the duke demanded respect, and when his wife did not do so, he got rid of her. He ominously mentions:
Oh, sir, she smiled, no doubt,
Whene'er I passed her; but who passed without
Much the same smile? This grew; I gave commands;
Then all smiles stopped together.
The vain duke instructed someone to silence his wife, and the words "all smiles stopped together" are a sinister indication that he had rid himself of a wife he most obviously did not love or desired.
The lesson to be learned from this is that one should respect others equally and not demand respect. Respect breeds respect, and the duke did not have any for his wife. He wanted her to obey him slavishly and have eyes for him only.
Furthermore, one should enjoy the little things in life as the duchess did. The duke, however, is all about title and possession—a fact which is encapsulated in his assertion to the Count's messenger that:
The Count your master's known munificence
Is ample warrant that no just pretense
Of mine for dowry will be disallowed;
Though his fair daughter's self, as I avowed
At starting, is my object.
In these words, the duke makes it chillingly clear that his interest in the Count's daughter is for financial gain and that, to him, she is merely another trophy.