This section presents three theories of views of the mind: (1) Type Identity, which holds that the general kinds of mental states we possess are identical to types of brain states; (2) Functionalism (also known as Token Identity), which holds that our mental states can be understood as the causal relations between typical environmental causes or stimuli, their behavioral effects and, most importantly, their causal relations with other mental states; and (3) Eliminative Materialism, a more radical view that our commonsense conceptions of mental states, like being in pain, tasting an apple, or thinking about Descartes, will one day no longer be useful to us at all and can be eliminated and replaced by more precise, neuro-scientific terminology.
Each of these views contrasts with our previous readings on Substance Dualism and Logical Behaviorism as well as with each other. The Type Identity theory of the mind is a materialist or physicalist view of the mind since it holds that our mental states, being identical to brain states, must be physical states. The Type Identity view thus seems immune to the kinds of criticisms Gilbert Ryle raises against the Cartesian view of Substance Dualism. At the same time, the Type Identity theorist does not agree with Ryle that our mental state language (terms) is explained solely on the basis of observable behavioral descriptions. The “Official Doctrine” misleads us into believing that there is an entity, “the mind,” that is a distinct, unobservable entity that is the cause of our behavior. For the Type Identity Theorist, there is a “mind” and it is the brain. The types of mental states we have are identical to types of brain states. Our first selection of this section, J. J. C. Smart’s “Sensations and Brain Processes,” presents his view of the way in which mental states, such as a sensation of pain, are identical to a kind of brain state, “C-Fibers firing.” These brain states are completely physical. Ockham’s Razor, the principle that advises us not to multiply entities beyond necessity, has inspired Smart to defend a materialist view of the mind that does not merely correlate mental states like sensations with brain states, for this would leave us with an extra feature of the world that would need explanation. At the same time, Smart wants to avoid a position that denies that our claims to be in mental states (our mental state terms) refer to a “ghostly” entity “the mind,” or have no meaning at all, or are terms that can be eliminated—simply translated into a description of a type of brain state and done away with. Whenever we report being in a mental state, Smart believes that this kind of report refers to the brain process that it is, but it does so “neutrally.” As stated in his paper, Smart’s example in his reply to Objection 3 is that when a person reports “I see a yellowish-orange after-image,” what this person means is that there is “something going on which is like what is going one when I have my eyes open, am awake, and there is an orange illuminated in good light in front of me, that is, when I really see an orange.” The person’s report of the after-image, her mental state, is not itself committed to dualism or materialism. It simply tells us how the state relates analogically to other mental states and their qualities. Thus, when we speak of our mental states, we are not committed to the idea that there are non-physical mental properties or physical properties. Sensations and all mental states are strictly identical to physical states, but our reports about them are neutral. Our mental state terms and reports about our mental life, in short, do not need to be rejected, even though these are identical to brain states.
Smart’s adherence to “strict identity” certainly helps him maintain adherence to Ockham’s Razor: Mental states are nothing over and above types of physical brain states, yet we might question how a strict identity can truly be maintained. A common criticism of Type Identity is that our mental states could not be strictly identical to brain states given “Leibniz’ Law,” that strictly identical entities share all properties in common. Granting Smart that our reports of mental states refer to types of brain states, how are the qualities of a sensation like seeing a red apple—the qualities of this experience—identical to a type of brain state, a particular stimulation of the visual cortex? The qualities that a neuro-scientist would use to describe the latter do not appear to be identical to those of the former. This sort of criticism will appear frequently against materialist and materialist-friendly views of the mind (like functionalism). It may remind us of Descartes in that these critics will wonder how the qualities of our mental states can be at the same time wholly identical to the qualities of physical states, but we should notice a significant change to Property Dualism. This sort of criticism does not hold that the mind is necessarily a completely different substance than that of physical bodies, rather it holds that mental qualities must be substantially different from physical qualities.