 Some care is required in determining what the relevant environments are. What matters is not only the environment the subject is currently in, but rather the environment in which the subject acquired the relevant beliefs and other mental states. If we zipped Oscar to Twin Earth and Twin Oscar to Earth, we would not thereby change what their thoughts are about (at least not immediately). Oscar would still be thinking about water, and would probably misidentify XYZ as water; Twin Oscar would still be thinking about XYZ, and would probably misidentify water as XYZ. What determines the broad content of their thoughts is not merely the environment they are in at the moment, but also the environment in which they first acquired their thoughts and beliefs about watery stuff. Provided we understand “context” to include both sorts of facts, we can describe the mapping conception as a conception on which narrow content is a function from contexts to broad contents.