QuestionsIs the mind the brain?Sensations are brain processes, as lightning is an electric discharge
Is the mind the brain?The mind comes from matter

Sensations are brain processes, as lightning is an electric discharge

The mind-brain identity theory

J. J. C. Smart 1920 · 2012Sensations are brain processes: nothing in the world escapes physics.
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What it claims

Sensations are nothing "over and above" brain processes: what we report when we say "I am in pain" is in fact a brain process, as lightning is an electric discharge.

Why

Saying one has an orange afterimage is saying that a brain process is occurring; explaining it so avoids adding anything extra.

The same idea through history
Ullin T. Place1956Ullin Place proposes that "consciousness is a process in the brain" be treated as a reasonable scientific hypothesis, of the same kind as "lightning is a motion of electric charges", and not as a logical absurdity.
J. J. C. Smart1959J. J. C. Smart takes up Place's thesis, defends it against eight objections and specifies that "is" means strict identity here. He gives it its best-known form.
In short

"Sensations are brain processes, as lightning is an electric discharge" is an argument by J. J. C. Smart (Place, "Is Consciousness a Brain Process?", 1956; Smart, "Sensations and Brain Processes", 1959, 1959) on the question "Is the mind the brain?" (answer: the mind comes from matter). Its claim: Sensations are nothing "over and above" brain processes: what we report when we say "I am in pain" is in fact a brain process, as lightning is an electric discharge. According to AskPhilosophy's logic check (Z3 solver), the conclusion does follow from its 4 premises. AskPhilosophy presents 3 objections, 3 of them with a documented reply, and the original text behind each premise, checked word for word.

Place, "Is Consciousness a Brain Process?", 1956; Smart, "Sensations and Brain Processes", 1959
Valid

When you are in pain, something happens in your brain. But is the pain something else that goes along with that process, or is it that process? In 1956 Ullin Place answers: pain is a brain process, in the same way lightning is an electric discharge. It is not true by definition, it is a possible discovery of science. In 1959 J. J. C. Smart defends the idea in detail. This theory, called "the identity theory", became the first modern form of materialism about the mind.

P1We can identify consciousness with a type of brain process if we can explain what people say about their sensations (their "inner" observations) by the brain processes with which they are correlated.
P2It can be explained like this: when someone says "I have an orange after-image", he is only saying that something is going on in him which is like what goes on when he really sees an orange. These words are neutral: they do not say what kind of thing is going on, or whether it is a brain process. The report of a sensation therefore needs no special, "mental" property over and above those of the brain.
P3Two expressions can differ in meaning, and even be learned with no knowledge of each other, and still name the same thing: "the Evening Star" and "the Morning Star", "lightning" and "electric discharge". That "sensation" and "brain process" differ in meaning does not show that they are two things.
P4According to science, there is nothing in the world but increasingly complex arrangements of physical constituents. If we can avoid adding, for sensations alone, things or properties of another kind that obey no physical law, we should avoid it (Occam's razor).
P5 · implicit premiseIf a sensation can be identified with a brain process, if the difference in meaning does not prevent it, and if simplicity of explanation favours this identification, then we should accept that the sensation is a brain process.
Therefore sensations are nothing "over and above" brain processes: what we report when we say "I am in pain" is in fact a brain process, as lightning is an electric discharge.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P5, one could accept P1 to P4 and remain a dualist: one would say that the identification is possible but that simplicity does not settle it, and that a lived experience (red, pain) has an aspect that physics does not describe. This is what the objections of Kripke and the defenders of qualia contest.
The argument is valid. P1 and P2 give the possibility of identifying the sensation with a brain process. With P3 (the difference in meaning is no obstacle) and P4 (simplicity), the hidden premise P5 concludes. The debate is mostly about P2 (are reports of sensations really "neutral"?) and P3 (can an identity between things so different be merely contingent, like lightning and the discharge?).
Analogy. In the 19th century it was discovered that water is H2O and that heat is the motion of molecules. Nobody said: "There is water and, in addition, H2O accompanying it." Place and Smart propose that science may one day make the same discovery about pain.

Objections

3

Each objection is a conversation: click to see who replies and where the debate stands.

J. J. C. Smart (an objection he treats himself, after Max Black) 1959 · attacks premise 2

Even if a sensation is not a thing "over and above" the brain process, its qualities may be: an after-image is yellowish-orange, and no brain process is yellowish-orange. As with the Morning Star and the Evening Star, two sets of properties are needed to recognise the same thing in two ways; "mental" properties would then remain irreducible.

Smart replies
J. J. C. Smart 1959 · Smart's reply (the "topic-neutral" reply)
Smart replies that someone who says "I see a yellowish-orange after-image" is only saying: something is going on in me which is like what goes on when I really see an orange. The words "something is going on which is like what is going on when" are neutral, neither dualist nor materialist. This explains how an ancient Greek peasant can speak of his sensations knowing nothing of the brain.
J. J. C. Smart 1959 · What Smart himself admits
Smart writes that the strength of his reply depends on being able to report that one thing is like another without being able to state the respect in which it is like. He is not sure this is possible, which is why he regards this objection as the strongest of those he considers.
The debate goes on (our summary) The debate goes on (our summary). Defenders of qualia (Nagel, Jackson, Chalmers) hold that the "what it is like" aspect of a sensation is not neutral at all, and that Smart dismisses it instead of explaining it. Defenders of identity answer that this is exactly what has to be shown, not assumed.
J. J. C. Smart (an objection he treats himself) 1959 · attacks the conclusion

That we have a certain sensation when a certain process occurs in the brain is only a contingent fact: our theories of the brain might one day prove false, like the old theory placing thoughts in the heart. So when we report a sensation, we are not reporting a brain process.

Smart replies
J. J. C. Smart 1959
Smart grants that "I have an after-image" does not mean "I have such and such a brain process", but replies that this does not show that what we report is not a brain process. "I see the Evening Star" does not mean "I see the Morning Star", and yet "the Evening Star and the Morning Star are one and the same thing" is a contingent proposition. So there can be contingent identities.
Saul Kripke 1980 · Counter-reply: the identity cannot be contingent
Kripke writes that, if "pain" and "C-fiber stimulation" are rigid designators, the identity of pain with that brain state, if true, is necessary. He adds that this reverses the usual opinion, according to which the identification of pain with C-fiber stimulation would be contingent.
The debate goes on (our summary) The debate goes on (our summary). Defenders of identity answer Kripke by saying that the illusion of contingency can be explained otherwise (Hill 1997, Loar, a posteriori physicalists). See the argument "Kripke, the modal argument".
Hilary Putnam 1967 · attacks the conclusion

If pain were identical to one type of brain state, one would have to find a single physical-chemical state that is a possible state of a mammalian brain, a reptilian brain and a mollusc's brain (octopuses are molluscs and certainly feel pain). Putnam finds it "overwhelmingly probable" that such different brains are in different physical states for one and the same psychological state (for example being hungry): pain would then not be identical to a type of brain state. See the multiple-realizability argument.

Smart replies
J
Jaegwon Kim 1992 · Kim's reply (local reduction)
Kim does not dispute multiple realizability, but denies that it refutes all reduction. If each species has its own physical basis for pain, each species' psychology can be "locally" reduced to its physics: bridge laws restricted to a species or structure type allow this local reduction, as unrestricted laws would allow a "global" one.
The debate goes on (our summary) The debate goes on (our summary). Place and Smart were thinking of human pain: their thesis can remain true for humans, for a species or a structure type. But Kim himself admits that in this case pain as a common kind does not survive, and most philosophers of mind followed Putnam and gave up identity between types.