Microphysical duplicates

Given physicalism, the thesis of phenomenal internalism reduces to the thesis that it is metaphysically impossible for microphysical duplicates to differ with respect to the phenomenal character of their internal states. To refute this thesis, it suffices to produce an example of two entities that are microphysical duplicates in some metaphysically possible world W without the two entities being phenomenal duplicates in W. It is to the task of constructing such an example that I turn in Sections I and II. 

In my view, then, the Xenon example provides us with a possible case in which a standardly embodied creature with a brain and a microphysical duplicate of that brain differ phenomenally. It does not yet show that microphysical duplicates can differ phenomenally. However, there is... 

This view will not be shared by everyone. Some will no doubt dig in their heels and insist that XPi is a brain and that it does have phenomenally identical experiences for the fifteen-minute period, however strange that initially seems. StiU at a minimum, even those philosophers who react in this way should agree that the example raises a serious doubt as to whether any two microphysical duplicates must be alike phenomenally. Thus, the Xenon tree example at least that phenomenal internalism is not a position that is self-evidently tme or one that cannot reasonably be disputed. 

A fourth reason (suggested to me by Cory Juhl) appeals to causal considerations. Consider a microphysical duplicate of the present time slice of our world (call it MD) that (a) is governed by the same physical laws as our world and (b) is the initial slice of a world, W, with no history prior to the present time. If the physical world is causally closed, then W will unfold physically just as the actual world will. So, future behavior in W will be the same as in our world. Now, given that phenomenal externalism imposes some sort of backward-looking tracking requirement on phenomenal character, since MD is the first time slice of I, there is no phenomenal character tokened in Wat the present time. MD, then, is a zombie replica of the current time slice of the actual world. But if this is the case, then... 

Microphysical duplicates situated in different surroundings do not differ in their P-properties. 

A microphysical duplicate of in a petri dish has no phenomenal character. 

The reasoning behind (4) is simply this. Suppose that there is a microphysical duplicate of in a petri dish. This duplicate will be a certain connected structure of firing patterns in an appropriate group of neurons in the dish. However, there won t be any token experience in the petri dish. For, patently, there is no subject in the dish to have an experience and, as noted in Section 1, experiences cannot exist unowned. But if there is no experience in the dish, then there is no entity in the dish having phenomenal character. And if this is true, then (4) follows. 

Instead of holding that intrinsic duplicates cannot differ phenomenally and thus that microphysical duplicates cannot differ phenomenally, if physicalism is true, the internalist might now propose the following ... 

BT) Brains that are microphysical duplicates cannot differ phenomenally. 

The answer must be that it is the possession of the extrinsic property of being a brain or some other extrinsic property common to all possible brains that makes microphysical duplicates having that property phenomenal duplicates. This is because if the property, the possession of which determines that microphysically identical brains cannot differ phenomenally, is intrinsic, then it will be possessed by all those entities that are not brains but that are microphysical duplicates of brains. In that case, it will be necessarily true that any two entities that are microphysical duplicates and that possess the relevant intrinsic property common to all possible brains are phenomenal duplicates. The reasoning of Sections I and II, in connection with the Xenon tree thought experiment, shows that there is... 

However, the property of being a brain obviously is not a plausible candidate for the role of extrinsic property that guarantees phenomenal sameness in microphysical duplicates that are brains. So, what is the crucial extrinsic property It is, I suggest, radically unclear. Moreover, to suppose that there is such a property is to place an emphasis on the extrinsic that is not really in the spirit of internalism anyway. 

BT ) Microphysical duplicates of structures consisting of brains appropriately connected to sense organs cannot differ phenomenally. 

BT- -) Structures that consist ofbrains appropriately connected to sense organs and that are also microphysical duplicates cannot differ phenomenally, the points made in connection with (BT), the first alternative proposal, apply mutatis mutandis. 

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