 A third type of response questions the legitimacy of the internalism-externalism debate. Gertler (2012), for example, has argued that there is no understanding of the distinction between internal and external properties, and related distinctions such as that between intrinsic and extrinsic properties, that will correctly categorize the views we take to be clearly externalist or internalist. If Gertler is correct, perhaps the most common way of understanding internalism, as the doctrine that content supervenes on the intrinsic properties of an individual, is unworkable. She therefore maintains that there is no genuine dispute at issue in the internalism-externalism debate, and recommends that philosophers drop the issue in favor of more well-defined questions. There is, more generally, an interesting question concerning how to understand the crucial distinction between a creature’s external properties and those that are intrinsic or internal. Many contributors to the debate over externalism take internal properties to be physical properties of a creature that do not depend for their instantiation on any property instantiated outside the boundary of the creature’s body and brain. A difficulty with this understanding of the distinction, pointed out by Farkas (2003), is that it appears to rule out the possibility of antiphysicalist internalists. This is ironic, given that Descartes is often held up as a paradigmatic example of an internalist about mental content. Williamson (2000) suggests that internalism can be understood as the doctrine that mental content supervenes on environmentally-independent phenomenal states, and Farkas (2003, 2008) makes a similar proposal.