Abstract
It is argued that the knowledge argument fails against externalist theories of mind. Enclosing Mary and cutting her off from some properties denies part of the physical world to Mary, which has the consequence of denying her certain kinds of physical knowledge. The externalist formulation of experience is shown to differ in vehicle, content, and causal role from the internalist version addressed by the knowledge argument, and is supported by results from neuroscience. This means that though the knowledge argument has some force against material internalists, it misses the mark entirely against externalist accounts.