 A second response takes us to the opposite extreme, extreme internalism. According to this response, Putnam’s and Burge’s examples do not succeed in showing that any content is broad. This position has been defended by, among others, Kent Bach (1987), Tim Crane (1991), and Gabriel Segal (2000). These authors question the externalist interpretation of the examples we have discussed. For example, in response to Putnam, Segal points out that we have some empty natural kind concepts — that is, we have concepts which we intend to be natural kind concepts, but which in fact do not succeed in referring to a real kind. Possible examples include the concepts of witches, ghosts, and phlogiston. In these examples, the environment cannot make the sort of contribution discussed by Putnam, because the environment contains no relevant kind. Nevertheless, people who have them use these concepts in their reasoning, and their behavior is partly explained by these concepts. If so, then we can have natural kind concepts that do not have an environmental component. Now, it seems that with respect to explanations of our reasoning and action, it does not make a difference whether the kinds we think we are reasoning about actually exist: so long as we think they exist, we will make the same inferences and perform the same actions regardless of whether we are correct or not. This may lead us to suspect that even in the case of non-empty natural kind concepts, our reasoning and action are best explained in terms of concepts whose content is not environmentally determined — in short, in terms of concepts whose content is narrow.