Unfortunately, mapping the landscape of computational difficulty has turned out to be, well, difficult. So in the mid-1970s, some researchers began to study what would happen if the rules of computation were different. That’s where oracles come in.
Like Magic 8 Balls, oracles are devices that immediately answer yes-or-no questions without revealing anything about their inner workings. Unlike Magic 8 Balls, they always say either yes or no, and they’re always correct — an advantage of being fictional. In addition, any given oracle will only answer a specific type of question, such as “Is this number prime?”