Externalism and Memory: Jane Heal

Tye claims that an externalist should say that memory content invoking natural kind concepts floats free of the setting where the memory is laid down and is at later times determined by the context in which the memory is revived. His argument assumes the existence of 'slow switching' of the meaning of natural kind terms when a person is transported from Earth to Twin Earth. But proper understanding of natural kind terms suggests that slow switching (contrary to what is often presupposed) is likely never to be completed. Hence the situation of a person unknowingly transported to Twin Earth is not that his memories switch content but rather than he gets two natural kinds confused.