Suppose a friend tells us something that happened with him and asks us to keep it a secret. Suppose it is nothing very important, but our friend thinks it is. Suppose the story could have been known by many people, because it happened in a public place, but in fact no relevant person knows of it, except for our friend and us. Do we have the duty to keep it a secret? It seems that if we have that duty, it is only because our friend asked us to do so. But do people have the power to create duties for other people only by asking them to do something?