 Close attention to the cases in which we credit someone for her performance shows that it is often enough for her (merely) to have satisfied certain criteria or for her performance to have lived up to the relevant standard. Close attention to the cases in which we require not only that she satisfy certain criteria but also that she apply the criteria by using an expression of a rule to guide her shows that the latter is in fact a separate skill, which we only sometimes (but importantly not always) demand of the one we wish to credit for her  performance.[8]