 Externalists argue that ordinary speakers are often ignorant or mistaken about the precise nature (modal profile) of the objects, kinds or properties their words pick out. But linguistic conventions don’t always fix the reference by specifying the nature of the reference. Perhaps the conventions governing names and natural kind terms are structured in a similar way to indexicals. For instance, we might have an implicit semantic rule requiring us to take ‘water’ to pick out whatever chemical kind actually explains a certain suite of superficial observable properties: e.g., being a clear, potable, odorless liquid that fills lakes and streams around here (Jackson 1998a, 1998b). On this analysis, ‘water’ just is an implicitly indexical expression, picking out different chemical kinds depending on which world is actual. If this rule is what one must accept to count as competent with the meaning of the expression type ‘water’, then it is no surprise that competent speakers often fail to realize that water = H2O.