These poems both have a common theme: that of the improper and extraordinary possessiveness of men during the period. Both poems feature men who had deemed a woman their own, but could not have them.
Porphyria’s Lover features a man who has fallen in love and become obsessed with a woman named Porphyria. This man is, of course, her lover rather than one of her “vainer ties.” (24) The lover reveals himself to be obsessed with and angry at the woman for not making him her primary and only love: “Murmuring how she loved me—she/ Too weak, for all her heart’s endeavour,/ To set its struggling passion free/ From pride, and vainer ties dissever,/ And give herself to me for ever.”(21-25) Phrases such as “murmuring” and “too weak” both imply the anger that the lover feels towards this woman for not being only his, and implies the later rash action of murder. This anger can only come from a feeling of possession, as the situation they are in does not allow for closer ties, and he knows this, yet expects Poryphyria to be his and only his. As a result his anger is aimed at her, and he considers how exactly he can turn her into his, which results in the ending of her life.
My Last Duchess on the other hand features a different sort of possessiveness. Alfonso II considers the girl to have entered his class upon marriage, and as a result he expects her to behave in an amazed and honored manner. She is expected to change her manner entirely and belong entirely to him when she (most likely) had little involvement in the discussion of the marriage and was “exchanged” primarily for the name. Alfonso considers this to be an extraordinary gift and cannot comprehend her response: “She thanked men, — good! but thanked/ Somehow — I know not how — as if she ranked/ My gift of a nine-hundred-years-old name/ With anybody’s gift.” (31-34) His expectations are not met, and so he has her killed, as hinted at in this line: “I gave commands;/ Then all smiles stopped together.” (44-45) He gave his name, to him a valuable commodity, to this girl and she does not take the name seriously enough. As a result he decides that the girl needs to be replaced with someone more fitting, and has her killed.
Both pieces feature the treatment of women as possessions to negative ends. Poryphyria’s lover knows that she is something he cannot have, and thinks the only way to “take” her is to murder her and keep her for himself. If he can’t have her, no one should. Lucrezia’s life is exchanged for a name, and Alfonso II cannot comprehend why she is not more appreciative of his “gift.” As a result he has her killed and searches for a more appreciative replacement. The Duchess is considered by Alfonso II to be an exchangeable possession that is easily replaceable rather than a human.
In these poems the men treat the women not as people but as something they can do with as they please. This is, in my opinion, because the author wanted to imply the negative elements this outlook on humans can induce and allow.