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Do you believe in the existence of ghosts?
Literal
Ghosts-of existence [object-を] believe-[polite-ますか]?
A more formal phrasing for 'do you believe in ghosts?' Instead of asking about belief in the things directly, this version asks belief in their 存在 ('existence') — substituting the abstract noun for a direct object. A common rhetorical upgrade for formal or philosophical contexts; sounds more like a careful investigation than a casual inquiry.