When future historians look back on the strange beliefs held during our era, they’ll chuckle at the thought that so many people believed the mind is identical to the brain. As philosopher Bill Vallicella says , “Few philosophers nowadays would maintain the bald thesis that the mind is identical to the brain, but it is a view that one hears among the laity.” Vallicella explains why it’s improbable:
Given the self-evident necessary truth of the Indiscernibility of Identicals, if my mind is identical to my brain, then my mind and my brain share all properties: everything true of the one is true of the other, and vice versa. But it is clear that they do not share all properties. The brain is a physical thing with a definite mass, weight, location, size, shape. One can inject dyes into various of its subregions. One can insert electrodes into it. One can remove and discard parts of it. One can add parts. I can literally give you a piece of my brain. (And you hope I won’t.) But can I literally give you a piece of my mind? Does my mind have a weight in grams? Is it divisible? Do my thoughts have a location or a volume? If one thought has a second as its object, as when I reflect, is the second thought located above the second? How far above? Can we intelligibly speak of the voltage drop across a thought?
It is true that my mind is now wholly occupied with the mind-body problem. But it is either false or makes no sense to say that my brain is now wholly occupied with the mind-body problem. It follows from these facts alone that my mind and my brain cannot be identical. The argument is very simple, and because so simple, very compelling ( simplex sigillum veri ):
If x and y differ property-wise, then x is not y.
Mind and brain differ in respect of the property of being wholly occupied with the mind-body problem.
Mind is not brain.
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