A person's dæmon is usually of the opposite sex to its human; however, very occasionally, it may be the same sex as the person. Pullman has admitted that the reason for this is unknown even to himself, and has agreed that it may also indicate some other gift or quality, such as second sight, or that the person is homosexual, adding "There are plenty of things about my worlds I don’t know, and that’s one of them". The single reference to such individuals is in "Northern Lights", where their rarity is established.