Most people, at some point in their lives, have noticed the uniqueness and complexity of the human mind. Unlike other substances, we cannot sense its being, see its color or feel its shape. But on the other hand, the mind contains our bodily sensations and even controls our movements. The constant talk inside that tells our stories and plans our future is too vivid for us to deny the existence of a mind. However, it seems hard to accommodate the mind in the material world of advancing natural sciences; then is the mind material or something else? Such question has raised the Mind-Body Problem, in which any three of four intuitively true propositions jointly entail a contradiction.
The propositions are as follows: (1)The human body is a material thing; (2)The human mind is a spiritual thing; (3)Mind and body interact; (4)Spirit and matter do not interact; (Mind-Body Problem Handout) where something material is defined as “spatial and subject to physical law”, whereas something spiritual is defined as “neither spatial nor subject to physical law” and having “consciousness and intentionality” (Mind-Body Problem Handout). Philosophers have been trying to solve this problem by objecting one of these four propositions.
Among them, Smart’s identity theory denies proposition (2) (“the human mind is a spiritual thing”) and claims that processes and states of the mind are identical to those of the brain. Different from the property dualist who argues that these mental processes and states are merely correlated with brain activities and yet are still spiritual, the identity theory places an equal sign between the mind and the brain, denying all its non-physical properties. Though the theory has solved the problem of mental causation (i.e. difficulty to know how mind and body causally interact if one is spiritual and the other material), it also implies that the only way to understand the mind – or the brain – is the neurophysiological approach. Thus, touch is just sensory neuron firing, joy is just the release of dopamine, intimacy is just the level of oxytocin, and many of our actions are merely conditioned reflexes. I think the most serious objection to the identity theory is objection 4.
It argues that the afterimage of seeing green is pinkish, and nowhere in physical space; however, the brain processes all take place in physical space, and none of them are pinkish. So the after-image cannot be identical to any of the brain processes. This objection seems plausible using Leibniz’s principle of the indiscernibility of identicals: if two things are identical, then the ‘two’ things must be indiscernible and so qualitatively the same. The brain processes, as described in neuroscience, are neuron firing and neurotransmitters releasing, which are all activities that can be located in a certain part of the brain (e.g. planning ahead happens in the prefrontal cortex and production of language happens in the Broca’s area, etc.). On the contrary, mental processes – the after image, for instance – has no such spatial property: As we look around, the after image turns as well. Also, the after image has a color, whereas we cannot say that the brain processes change color when we see certain images. According to Leibniz’s principle, such differences entails that the mental states cannot be identical to the brain process. Xinyu Kang Student ID: 1004894359 TA: Molly Dea-Step henson However, this objection does not refute the identity theory successfully.
Smart replied by distinguishing between mental states and mental objects. He argues that the after image itself is just a mental object and that it is the state of experiencing a pinkish after image is the mental state which is identical to the brain state. Therefore, the experience can again be located in the brain as any other brain processes, and certainly, the processes do not have any color. It is similar to pain. When we have a paper cut, we would not try to find a “pain object” on our finger and heal it by removing it. Although we are experiencing a painful finger, the pain is actually in the brain, where the central neural system receives information about the cut through neural pathways. Thus, it is meaningless to insist on locating these mental objects in the physical world or identify them with any brain activities. As for me, the identity theorem seems quite plausible. The constant development of science is increasingly turning mysteries into mathematical formulas and physicochemical properties. More and more “unexplainable” behaviors and cognitions of the human mind are currently explained through scientific approaches. With some knowledge of cognitive science and neuroscience, it is conceivable that the mind is identical to brain processes and one day we may locate any mental states in the brain.
However, I still think that we should be more cautious about using the equal sign between the mind and the brain. There are still too much unknown to us. For example, a person may have billions of thoughts in their entire life. We would be able to categorize these thoughts into different hemispheres, cortexes, or even small regions of the brain, but it is most likely the case Xinyu Kang Student ID: 1004894359 TA: Molly Dea-Step henson that two distinct thoughts – or mental states – can be located in the exact same place with the same physical constitution which produces them. With the logic from Leibniz’s principle of the indiscernibility of identicals, it could imply that they are not the same thing. In conclusion, Smart’s identity theory denies all the spiritual properties of the human mind and argues that it is identical to brain states. When defending his theory against objections, he clearly distinguished the concepts of mental objects and mental states. Although his view correlates to scientific development, we should not be so confident to assume the unknown
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