The duke did not consider his wife to be more than a simple object, as he almost identified her with a painting. Furthermore, he believed his wife to be similar to something that could simply be replaced when it finished serving its purpose.
It seems that the duke does not actually want his listener to become acquainted with the fact that he had been responsible for his wife's death. Being captured in the monologue, he constantly gives clues that have the audience become more and more certain that the duke's dissatisfaction with his wife behavior had materialized in her death. Because of the stressful situation, the duke's speech is disorganized and full of anger, revealing the fact that "his" duchess had performed a great deal of actions that had come against the duke's principles.
According to the duke, Fra Pandolf had succeeded in capturing the exact expression that the duchess had at the time. In addition to that, he tells his listener that "twas not Her husband's presence only, called that spot of joy into the Duchess' cheek." (lines 13-15) Apparently, the duke believed that the duchess's joy had also been a product of other factors, such as the other men involved in her love-life. The duke's convictions became even more certain when he learnt that his wife's look had been so obvious that even the monk had observed "the faint half-flush that dies along her throat." (lines 18-19) the flush suggests that his wife had all the reasons to feel guilty because of her behavior.
Consequent to describing his wife expression from the painting, the duke continues with having the audience learn more of his wife's nature. "She had a heart -- how shall I say? -- too soon made glad, Too easily impressed; she liked whate'er She looked on, and her looks went everywhere."...
The duke tends to hesitate from time to time, as the phrase "how shall I say?" directly proves that he did not know exactly how to convey his words so that the audience would not become too familiar with the situation that the duke and his wife had been in. In spite of the fact that the duke wants to give limited information relating to his wife and to their relationship, he cannot resist mentioning the fact that he could no longer stand her immoral conduct.
The duke had been a very arrogant man that considered himself to be superior to others and especially to his wife. As a result, he felt wretched when he had learnt that his wife had not appreciated his "gift of a nine-hundred-years-old name," (line 33) What is more disturbing is that he had also learnt that his wife had dared to disdain his valuable "gift."
The duke admitted that the duchess did not refrain from smiling every time they met. However, to his dissatisfaction, the duchess apparently produced the same smile whenever she met someone. Considering that this had been the last straw, the duke came to the conclusion that something needed to be done in order for him to gain his pride back. Consequently, he "gave commands; Then all smiles stopped together." Most probably, the commands that he had given had not just stopped the smiles, as they had also stopped the Duchess from living.
The fact that the duke did not consider his wife to be more than an object is also revealed to the end of the poem, when he presents the audience with a painting of the god Neptune "taming a sea-horse," as if there had been no difference between this painting and the one discussed before.
