I came across the subject argument this week. The argument is prefaced with the statement that by definition, personhood depends on consciousness at any extent, the capacity of cognition, and the capacity to interact with other persons. All of these things are then categorized as "mind" and, therefore, a mind of some sort is necessary for personhood. I agree that a mind is necessary for personhood.
It is also prefaced with the statement that a material, computational substrate (a brain) is a necessary condition for the existence of a mind. Five scientific facts are provided to bolster this statement. The only fact I see as debatable is number 1, however, for the sake of argument, let us grant all of these as facts. Here they are:
F1. The evolution of species demonstrates that development of the brain obtains a corresponding mental development.
F2. The same principle is demonstrated by brain growth in individual organisms.
F3. Brain damage destroys mental capacities.
F4. Experiments and measurements on the brain (EEG, stimulation of various areas) indicate a correspondence between brain activity and mental activity.
F5. The effects of drugs show correspondence between brain activity and mental activity.
Let us grant the conclusion; a brain is necessary for the existence of a mind. Since, we agreed above that a mind is necessary for personhood, it follows then that the existence of personhood requires a brain as well based on the conclusion in the previous sentence.
Now, here is the argument:
1. None of the organic minds we have observed can exist without a brain. (from F1 to F5)
By induction, we obtain:
2. Probably, no organic mind can exist without a brain.
To be fair, we do not expect a hypothetical god to have an organic mind. So we extend 2 to:
2b. Probably, no mind can exist without a material, computational substrate.
3. A god cannot be material.
4. A god, if it exists, has a mind.
5. Probably, gods cannot exist. (from 2b, 3 and 4)
I think this argument falls right out of the starting gate with premise 1. Here is why. First, we agree that a mind is necessary for personhood, however I see no reason to think that personhood is "organic". Consciousness, cognition, and interaction with other persons are not organic objects. Further, if personhood and the mind are nothing but organic brain activity, the first premise should read "None of the brains brains have observed can exist without a brain" for the prefaced language and "facts" make personhood, the mind, and the brain all synonymous. I see no reason to think that this is the case. We clearly see this association in the "generosity" to extend premise 2.
Second, I do not understand how premise 1 is deduced from F1 through F5. I think at most it can only be deduced from these facts that brain activity and mental activity are correspondent.
Those are my thoughts (And only I could have revealed them. No one could have determined them by examining my brain activity) on where I think this argument fails. Feel free to leave your thoughts on the merits or failings of the argument.
Stand firm in Christ,