P| 1. According to Type-Type Identity Theory each mental property M is identical with a particular physical/neural/brain property P (e.g. Pain = chaotic firing in ACC).
1| 2. Thus if Type-Type Identity theory were true a creature that did not have the specific neural property P could not have the mental property M (e.g., if it does not have chaotic ACC firing, it cannot be in pain).
P| 3. However, there are creatures with nervous systems very unlike our human brain - e.g. birds, frogs, or octopi - that cannot have property P (e.g., they have no ACC), but they can and do still have property M (e.g., they feel pain).
2,3| 4. Type-Type Identity Theory is not true.
• Fallback position- relativize the property identity to the particular species, like identifying human pain with acc firing rather than pain with acc firing
• Reply- doesn't escape multiple realization because even in humans different neural states may realize the relevant mental states. Ex: one neural state realizes a persons memory one day and then another state another day