The American philosopher Hilary Putnam (1926 — 2016) is vitally important in the history of functionalism, at least as it applies to the human mind. Interestingly, he turned against functionalism in the late 1970s. The paper analysed in this essay (‘Philosophy and Our Mental Life’ — 1975) is only mildly critical of functionalism. (Putnam specifically argues against his former position of machine-state functionalism.) In any case, in order to get his functionalist point across, Putnam discussed what he called “immaterial brains” and “material souls”, stressing that in both cases if what matters are “functional states”, then such entities are possible.
[See my follow-up essay, ‘Functionalism vs Materialism’.]
One central idea of functionalism was expressed very simply by Hilary Putnam. He wrote:
“I explained the most general notion of functional isomorphism by saying that two systems are functionally isomorphic if there is an isomorphism that makes both of them models for the same psychological theory.”
Putnam then really got down to the nitty gritty of functionalist isomorphism. Take his own example:
“[A] computer made of electrical components can be isomorphic to one made of cogs and wheels. In other words, for each state in the first computer there is a corresponding state in the other, and, as we said before, the sequential relations are the same — if state S is followed by state B in the case of the electronic computer, state A would be followed by state B in the case of the computer made of cogs and wheels.”
More importantly and relevantly, Putnam continued: “[I]t doesn’t matter at all that the physical realizations of those states are totally different.”
This is all very well when it comes to computers made of electrical components and computers made of cogs and wheels. However, does all this pass over to minds, brains and mental states? Indeed, even in the case of computer states, we’d still need to know exactly what they are regardless of the fact that state S is followed by state B, and state A is followed by state B.
Putnam on Souls in the Soul World
Bizarrely, Putnam discussed “souls in the soul world”. These souls are “functionally isomorphic to the brains in the brain world”. Yet souls are supposed to be non-physical (or non-corporeal). This means that the pains of souls can’t be realised by physical brains. (They aren’t realised by anything!) Souls may not be abstract, but they aren’t physical either. The fact that souls aren’t brains wasn’t important to Putnam’s functionalism. Indeed, Putnam continued by asking the following questions:
“Is there any more sense to attaching importance to this difference than to the difference between copper wires and some other wires in the computer? Does it matter that the soul people have, so to speak, immaterial brains, and that the brain people have material souls?”
Putnam brought in soul people to get his point across. It’s rather an extreme example. Talk of “immaterial brains” and “material souls” certainly seems very odd. Yet from a functionalist perspective, it isn’t. After all, Putnam interprets brains and souls functionally. That means that brains can be immaterial, and souls can be material. What matters to a brain being a brain, and a soul being a soul, is their functions. And, in this case, their functions are the same, or at least similar.
Actually, in this case, Putnam concluded by referring to a “common structure”, not common functions. He told his readers that “[w]hat matters is the common structure [ ] and not the hardware”. That’s not a problem because functions have structural explanations.
Putnam on Clairvoyance, Telepathy and Reincarnation
It’s worth adding here that Putnam’s talk of “souls” and the “soul world” didn’t mean that he had gone all religious, and then dressed that conversion up with technical talk about “functions” and “states”. Instead, this example (as already stated) was his outré means to get his point across. After all, Putnam wrote:
“If it is built into one’s notions of the soul that the soul can do things that violate the laws of physics, then I admit I am stumped.”
More relevantly to functionalism:
“There cannot be a soul which is isomorphic to a brain, if the soul can read the future clairvoyantly, in a way that is not in any way explainable by physical law.”
However!
Putnam provided his readers with a big but. He continued:
“On the other hand, if one is interested in more modest forms of magic like telepathy, it seems to me that there is no reason in principle why we couldn’t construct a device which would project subvocalised thoughts from one brain to another.”
And then Putnam became even sexier:
“As to reincarnation, if we are, as I am urging, a certain kind of functional structure, there seems to to be in principle no reason why that could not be reproduced after a thousand years or a million years or a billion years. Resurrection: as you know, Christians believe in resurrection in the flesh, which completely bypasses the need for an immaterial vehicle.”
It’s not immediately clear how adopting functionalism would help with projecting subvocalised thoughts from one brain to another via some kind of physical device. Unless seeing such thoughts in exclusively functional terms (i.e., as functional states) would help with this project. After all, the physical basis of such thoughts couldn’t be projected from one brain to another.
As for reincarnation.
If the mental lives of human persons are given an entirely functional description, then that description can be captured in a program. (Spiritual and religious thinkers stress “information” when it comes to reincarnation, not functional states.) This example, then, clearly relates to the one just given about the projection of subvocalised thoughts. In both cases, a functionalist account and approach makes everything so much simpler. The messy details of the body and brain can simply be dispensed with.
Putnam on Martian Pain
Putnam then brought on board the multiple realizability argument again. He wrote:
“It is as if we met Martians and discovered that they were in all functional respects isomorphic to us, but we refused to admit that they could feel pain because their C fibers were different.”
Readers may wonder how human persons could ever discover that Martians are in all functional respects isomorphic to us. After all, Putnam wasn’t hinting at analysing their brains. Instead, he must have meant that they (may) behave like human persons when they’re in pain. Thus, such functional respects must be derived from the behaviour of Martians.
Putnam’s point was that pain is multiply realizable. Yet how could he have known that? Was it entirely due to the behaviour of entities which aren’t human persons?
Putnam never actually mentioned behaviour in these passages. However, the gist of what he did say is indeed Wittgensteinian and/or behaviourist. In other words, if Martians behave as if they’re in pain, then they must be in pain. Yet Martians’ brains don’t contain C fibers. [See note.] So their pains must be realised by physical elements which aren’t C fibers. The upshot here, then, is that pains can’t be identical to the “firing” of C fibers.
Note:
(1) The idea of “C-fibers firing” was often used in the philosophy of mind. It’s still used today as an example of mind-brain identity, even though many philosophers (including materialists/physicalists) now view it as being too simplistic.
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