When the cardinals enter the Sistine Chapel on Wednesday at the start of conclave, the process of electing a new pope, they will be sealed off from the world.

A papal conclave blends the political and the spiritual, cardinals and theologians say. Here, in Catholic belief, is how the Holy Spirit fits in.

Cardinals electing a new pope have some fundamental questions to weigh, beyond whether to give the Catholic Church its first Asian or African pope.