 It seems plausible that narrow contents must be more discriminating than this. YVH introduce several examples to show that indices for narrow contents must include an agent parameter as well as a world parameter (pp. 69–71). To take a slight variant of the simplest one, suppose that Varnsen and Twin Varnsen are sitting in identical offices, and each is thinking “I am in room 250.” Varnsen is in room 250, but Twin Varnsen is in room 251, so their thoughts have different truth values. The thoughts occur in the same possible world and have (since the two are duplicates) the same (narrow) content. This is not possible if indices contain only a world parameter, but if there is also an agent parameter, then the differing truth values are not a problem, since the thoughts occur in, and are therefore evaluated at, different indices. Similar considerations show the need for a time parameter in addition to world and agent parameters.