 If Dennett is right, there would be reason for scepticism about what Hurley calls the isomorphism hypothesis. The isomorphism hypothesis is the idea that a given kind of change in consciousness will always reflect, even be the result of, a given kind of change in the brain. Hurley is sceptical about it, too. One way in which skepticism about this hypothesis arises in her work is via consideration of acallosals (people born without a corpus callosum). Even though the corpus callosum, when present, is the chief channel of communication between the hemispheres, acallosal people show all the behavioral signs of having fully unified consciousness. If so, it has to be achieved by mechanisms such as cuing activity that are utterly different from communication though a corpus callosum. And the same can be true the opposite way. Different changes in consciousness can go with the same changes to structure and function in the brain. And if both these claims are correct, then the neurological/behavioral basis of unified consciousness would be very different in different people. The isomorphism hypothesis would be false, attractive though it has been to many people.