As the title, the phrase "a dream within a dream" has a special significance to any interpretations of the poem. Poe takes the idea of a daydream and twists it so that the narrator's perception of reality occurs at two degrees of detachment away from reality. Consequently, this reality reflects upon itself through the dream medium, and the narrator can no longer distinguish causality in his perception. By showing the narrator's distress at his observations, Poe magnifies the risks of uncertainty and of the potential changes to his identity. Time is a powerful but mysterious force that promotes cognitive dissonance between the protagonist's self and his abilities of comprehension, and the daydream proves to have ensnared him. Alternatively, the poem itself may be viewed as the outermost dream, where the inner dream is merely a function of the narrator's mind.
The thesis statement serves as the foundation of any essay. Feature it prominently in the introduction, as the final sentence. The perspective you chose to take in the introduction drives the thesis statement. Consider your main idea and why it is important. For example, what influence did historical events have on the poem and why are they significant? Alternately, you might choose to answer the question of what the use of personification adds to the poem and why is it significant. To create a strong thesis statement, answer the questions you want to address in one assertive sentence.