What is the significance of Eleanor's repetition of the phrase "Journeys end in lovers meeting"?
In its traditional Shakespearean context, this phrase isn't disturbing, but in The Haunting of Hill House it plays a much more ambiguous and problematic role. Eleanor remembers it on her journey and repeats over and over to herself to the point that it becomes excessive and obsessive by the novel's end. Other characters say it once or twice, but we do not know if it is by her doing somehow. It can sum up what happens to Eleanor in a way, for Hill House is indeed her journey's end in more than one way, and that end comes with her meeting her love - the lover being the House, a home, a "mother," etc.
How does Jackson play with the dichotomies of inside/outside?
Jackson reverses our traditional associations with inside and outside. Normally "inside" is a place of refuge from the chaotic, confusing, and cutthroat "outside" world. However, in this novel the "inside" world of Hill House (and of Eleanor's former home life, for that matter) are not nourishing and secure. It is a place that suffocates and oppresses, that can attack and even dissolve the self. "Outside" is freedom. It is the wider world that may be difficult, but allows for growth, self-awareness, and freedom. Eleanor does not spend enough time here before she is thrust back inside and begins to surrender any autonomy and selfhood she'd gained.
Is Eleanor imagining the supernatural events? Is she causing them? Or is the House doing everything?
To put it simply, we don't know. All of these theories are possibly true, or true to an extent. There is no doubt that the House is evil; it is established by the objective narrator as such. It has been doing cruel things long before Eleanor got there, and it has elements of terror completely unrelated to her that all the others can sense, even Mrs. Montague and Arthur. However, Eleanor seems to have poltergeist abilities, as seen in the stones raining down on her childhood home, and it is possible that she wrote the messages and manifested the pounding noises and laughing through her diseased psyche. Or, she may been imagining some of them and the telepathic Theodora picks up on her feelings and thinks she is hearing them as well. We don't know, but that is part of the book's mystery and allure.
How does Jackson play with the passage and the sensation of time?
Almost as soon as Eleanor sets out on her journey time ceases to function in a linear, distinct way. There is a slowness, a haziness, a dreamlike element to it. The days are lazy and the characters forget what day it actually is and are cut off from the rest of the world. The House is silent and unchanging; it has been the same for eighty years and will be the same for the next eighty. The confusion of time works alongside the erratic and irrational nature of the house's design to discomfit the characters and lead to their break(s) with reality.
What role does religion play in the text?
Religion is not particularly prominent in the text except as it appears in Hugh Crain's perverse scrapbook to his daughter. He juxtaposes handmade drawings and clippings of disturbing artworks to illustrate warnings to his daughter about engaging in the seven deadly sins and exhorting her to remain pure and faithful so they can be reunited in the afterlife. Religion here is linked to sexuality in a distinctly repressed, Puritanical way. Consciously Crain is simply giving his daughter moral lessons, but he is actually revealing his more salacious, unconscious yearnings. All of this seeps into the very fabric of the House, giving it a lurid, perverted bent. Clearly, there is evil energy in the House and there is evil energy in the family.