The hypothesis of extended cognition holds that mental states and processes need not be wholly contained within biological confines. Yet the theory is plausible, and informative, only when it can set principled outer limits upon cognitive extension: it should not permit unrestricted expansion of the mental into the material environment. I argue that true cognitive extension occurs only when the subject takes responsibility for the contribution made by a non-neural resource, in a manner that can be illuminated by appeal to (...) theoretical resources from contemporary virtue epistemology. (shrink)