According to the reference on Linguistics, the definition of an allegory is:
"An allegory is an extended metaphor, especially a story in which fictional characters and actions are used to understand and express aspects of concepts relating to human existence."
Based on this definition, "The Lady of Shallot" relates to the lives of women in the Victorian period, the restrictions that were placed on them, the lack of choices they had and the domination of their lives almost exclusively by men.
If you look at the poem as an extended metaphor for the Victorian woman's lack of choice, the confinement of the lady in the tower can be interpreted as the control put on young women as a way to keep them protected from illicit experiences to preserve their purity so that when their father or male relative was ready to make a marriage arrangement they would be very marketable.
Victorian women were possessions in the eyes of their families, they were to remain close to home preparing for marriage,...
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