Because time is such a distorted thing in To the Lighthouse, memory and the past are a vital part of the characters’ present. When a single moment is given the tenth degree, every significant aspect of the moment is interrogated. It’s also important to note that a lot of important information is transferred via characters’ memories – which makes sense, since in real time the novel only truly covers one day.
Part Three of the novel cinches Lily Briscoe’s position as the book’s protagonist, as her memories and perspective on the past are the most telling and important.
The primary difference between Lily’s feelings in Part One and Part Two lie in the presence or absence of Mrs. Ramsay, and her feelings toward the past therefore mirror the conflict of her feelings towards Mrs. Ramsay.