- There is much to admire in this book. It is written in a pleasingly straightforward style, and offers insight on a wide range of important issues.
- The book's main topic is the unity of phenomenal consciousness. Phenomenal consciousness is the property that a mental state has when there is something it feels like to be in that state – experiences being the clearest example. Experiences are unified when there is something it is like to have them together: if I see a bird and at the same time hear it squawk, these experiences are unified; if you see the bird and I hear it, they are not. But this unity does not simply amount to the experiences' belonging to the same subject, Tye says, because in split-brain cases a single person might have simultaneous but disunified experiences. Tye's question is what phenomenal unity does amount to.
- Tye's final chapter ("Tye (Michael) - Persons and Personal Identity") appears to be entirely independent of his discussion of phenomenal unity. Here he makes three main claims. The first is that people necessarily match up one to one with "person-level psychological frameworks", which consist of the beliefs, desires, experiences and so on that explain a person's behavior (141). So a person x existing in one situation is identical with a person y existing in another if and only if the psychological frame- work that x has in the first situation is the very psychological framework that y has in the second.
- This proposal is less interesting than it sounds. It appears to imply that no person – none of us – can exist at a time without having a psychological framework. It follows that I was never an early-term foetus1: I came into being several months, at least, after I was conceived. But it is unclear what it implies beyond that. Could I survive a brain transplant2 (where the rest of me is destroyed)? Or Star Trek teleportation? In these cases the resulting being has got a psychological framework, and according to Tye he is me if and only if the framework he has then is the one I have now. But Tye doesn't say when psychological frameworks existing at different times are identical, and his opinions about who is who in these cases are based on other considerations.
- We might expect someone who held that people necessarily match up one to one with psychological frameworks to say that people are psychological frameworks – beings composed not of matter but of mental states. But this is not Tye's view. He says instead – and this is his second claim – that we are brains (142). Strictly speaking we each weigh less than three pounds. Most of us have never literally seen a person, and wouldn't want to. …
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