I have asked many children, “Do you believe that your mind is the same thing as your brain?”…Among those who answered no, one said, “The mind cannot be the same thing as the brain because the brain is something tangible and the mind is not.”
Raymond Smullyan, 2000 BC
I’ve always felt, justifiably or not, a similarity here with Saul Kripke’s argument against mind-body identity, which roughly amounts to this: mental properties are essentially mental, and brain properties are essentially physical, and thus they aren’t the same. If you grant that “tangibility” is a constituent property of physicality, or identical to it, the child seems to be making the same argument Kripke’s notion of “essentiality” derives from modal logic and possible worlds. In essence, since it is logically possible (to Kripke, anyway) to have a single mental state with different physical instantiations, it is not necessary that a mental state be correlated to any particular physical instantiation, and therefore mental states cannot be reduced to physical brain states.
I never engaged with modal logic, which Kripke establishes and relies on for his anti-identity argument, because it seemed more about a question of imagination than logical possibility (pace early Wittgenstein, in my opinion, though Kripke would not agree). And in Kripke’s defense, he appeals to an intuition that is so strong that it has the appeal of being possibly epistemically primary, enough so that a child naturally bifurcates the world into mental and physical in such a fashion. She can imagine clearly that her mental states have no necessary physical instantiation.
Intuitions are constantly overturned, but what is the etiology of the strongly held belief of mind-body non-identity, especially if it is not shared by all? Is it cultural conditioning, as with Greeks who saw the mind in the chest, or is it a more innate disposition? (Or are those other kids zombies?)
Either way, the ability to locate such intuitions in children is what gives Kripke’s mind arguments such force (if not persuasiveness). There is room for extending his other necessary/contingent arguments, like the business about the Morning Star and the Evening Star, over to Piaget’s developmental stages of object relations. If a star appears in the morning and the night, Kripke proposes that it’s not necessary that “the Morning Star” and “the Evening Star” be the same thing, even if in our world they actually are.
This distinctions are more meaningful to me psychologically and linguistically than they are metaphysically. At what point can a child know that the Evening Star and the Morning Star may (or may not) be one and the same thing? At what point is the distinction even meaningful?