Metaphysics of Mind, Part 1: Type Physicalism
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Hi. Thanks for tuning into Philosophical Investigations, the podcast all about philosophy with no prior knowledge required. In this episode, we’ll be beginning our miniseries on the metaphysics of mind by looking at type physicalism, its ramifications, and why it might not be the best view.
To begin, we should know what the debate is about. Metaphysics of mind is a topic in philosophy about the nature of the mind, largely centred around its relationship with the brain. In other words, what is the mind made of, and how does it interact with the body? Without getting too deep into it (we don’t want to spoil the next few episodes, after all), people traditionally believed in souls, which are more often called ‘minds’ in philosophy. These mind-souls were separate from the brain and had no physical presence, but still controlled the body somehow. That view fell out of favour around a hundred to a hundred-and-fifty years ago in favour of physicalism — the belief that there exist no non-physical things.
Chances are you believe this theory — or something quite like it. It’s a very common-sense view for people of today’s sensibilities, but there are multiple kinds of physicalism, all with different views on the exact relationship between minds and brains. Today, we’re looking at type physicalism, which is also known as type identity theory, mind-brain identity theory, reductive materialism, and a bunch of other names. The simple definition is this: that brain states and mental states are one and the same thing; but to really understand it, we’re gonna have to get into the real nitty-gritty, so here goes.
First, we need to understand what separates physicalism from other views generally, and to do that we need to understand what a substance is, philosophically-speaking. Definitions disagree, but generally, a substance is a basic part of the universe to which properties belong; by that definition, we might conclude that sub-atomic particles are the basic substances of the universe (or even smaller physical phenomena, as the case may be), which possess properties, such as charge and mass, and which come together to build other, bigger things. On this view, one kind of substance is physical substance: things made out of gluons and bosons and so ons are physical things. You can be a monist about substances, a dualist, a pluralist, or even a denier (we’ll get into that at a later date); physicalists are monists — they believe there is only one kind of substance, and that kind is, of course, physical substances.
It’s a little complicated to get your head around at first, but the concept of substances aims to help us in answering the question “What is the fundamental nature of reality?” What exists, and what can possibly exist? On a physicalist account, where there is no space for any non-physical substances, only physical things can exist. So here we have our first issue: if the universe contains no non-physical things, then there cannot be any such thing as a mind in the way we talked moments ago. This goes against our intuition — my mind doesn’t feel physical, like it’s a part of my body, and I can’t point to it — which doesn’t mean it’s wrong, necessarily, just that physicalism will have to do a good job of showing why our intuitions are wrong. And that’s why we have type physicalism — an attempt to explain away our intuitions by offering an alternative account of what the mind is and how it works.
So what’s meant by ‘type’? A type is a kind of thing, of course — two cars that share a make, model and year can be said to be of the same type, for example. Compare this to tokens — the individual cars themselves. To say Jenny and Carl drive the same type of car isn’t to say that they share a single car between them — they are simply produced to the same specifications. Similarly, mental states and processes can be broadly grouped into a number of different types; pain, for instance, is a type of mental state. Likewise, brain states and neurological processes can be broadly grouped into a number of different types; C-fibre firings is a classic example of a type of neurological event, for example. Of course, this isn’t to say that the events leading up to the pain or the C-fibre firings are always the same — a stubbed toe is distinct from a gunshot wound — but that the mental and neurological events that follow such misfortunes are similar enough to be grouped together.
And finally, we’ve reached the point of this long-winded explanation: according type physicalists, mental state types and brain state types are identical. Specifically, there are materially equivalent — remember that term from Episode 2? They’re two sides of the same coin: if and only if C-fibres are firing in the subject’s brain, then the subject’s mind will be in a state of pain; and, if and only if the subject’s mind is in a state of pain, then C-fibres will be firing in the subject’s brain. You can extend this further to say that a mental state of happiness is identical with a brain state of endorphin excretion, or that a mental state of depression is identical with a brain state of reduced serotonin activity. (And, of course, note that these paired mental and brain states can be updated when new neurological evidence shows a different, more accurate pairing.)
It’s easy to see why this view is so attractive to non-philosophers, even if it has fallen out of popularity among philosophers themselves. It’s a no-nonsense take in today’s secular, scientific world, and it quite neatly allows us to talk about mental states naturally, using regular everyday language, while understanding our mental states in physical, biological terms. In other words, this conclusion is not merely metaphysical, but semantic — it tells us a lot about the way we talk about mental activity. For type physicalists, talk about mental state types is reduceable to talk about brain state types. When someone says, “I’m happy,” we can accurately say that what they’re describing is a particular brain state type that is currently present in their particular brain. When a pharmaceutical company wants to treat depression, they can look at the chemical brain state identical with the mental state of a depressive mood and word from there.
The most powerful ramification of type physicalism may be its impact on the field of psychology and its status with the scientific fields of study. Many people today claim that psychology is not, in fact, a science; rather, they say, it is a pseudoscience — for whatever reason. Type physicalism would solve this issue, and here’s how.
The sciences are inter-related in a strict way. See, biology is largely reduceable to chemistry, which is in turn largely reduceable to physics, and physics is largely reduceable to basic observation on the one hand, and applied mathematics on the other. If psychology, and talk about mental states more generally, can be reduced to talk about brain states — which is biological in nature — then we can see how psychological study could be, eventually, be founded on physics and maths. Currently, psychology as a field of study is largely non-reductive, but if it can be reduced, it finds more favourable footing in the scientific community.
The second important ramification of this viewpoint is that it opens the door for determinism. Now, we’ll get super in-depth into determinism in a later episode, I’m sure, so for now we’ll just go over the highlights, but the broad message of determinism is that physical systems are determinative. If I push over a domino at the start of a sequence of dominoes, then without outside interference, and if they are lined up close enough, then the first domino will start a chain of events that causes — necessarily — the final domino in the sequence to fall over as well. And note the use of ‘necessarily’ here, in contrast to ‘contingently’; if the chain of events were non-determinative, then the chain of events that follows me pushing over the first domino could stop halfway through. In reality, the laws of nature necessitate that the chain of events can’t just stop of its own accord; the final domino falling is a necessary consequence, not a contingent consequence, of my pushing over the first domino, provided nothing else gets in the way.
We see this similarly in weather patterns, ocean currents, and so on: these physical systems obey regular laws and patterns of (non-cognitive) behaviour. Since, on the physicalist view, we are also entirely physical, including our mental states, then there is no reason to suppose that we would not also be subject to the laws and regular patterns of non-cognitive behaviour as well — just like weather systems and ocean currents. And, in much the same way as a butterfly flapping its wings in Europe could cause a hurricane in the US (an extreme example of course, but chosen for its popularity), so too could a lightning storm in Alabama affect my brain state, and consequently my thoughts, feelings and actions, in Stoke-on-Trent. What does this mean for free will — which is to say, the choice to do one thing or another without any sort of predestination? If someone were to know the precise state of every atom moments after the big bang, could they then follow that through to your birth, your performance at your first interview, the opinion of the interviewer, the transmission of COVID-19 from animal to human and what Patient Zero did after catching it? After all, it’s all one physical system on this view, with precisely no difference between individual types of mental state and individual types of brain state. The causal nexus, as it is known — the interconnected web of causation that extends throughout all of history and all the way into the future — is inescapable, if indeed both type physicalism and physical determinism are true.
(Wait, didn’t I say I’d be brief on determinism?)
Anyway, let’s talk about some of the criticisms of the theory. The first one’s pretty easy to defeat, so we’ll cover it quickly. The counterargument goes that “Pain” and “C-fibre firings” mean two different things: when I say “pain”, I’m picturing some sort of internal sensation; when I say “C-fibre firings”, I’m picturing some sort of neurological event. The response to this is based on a distinction made by a famous German philosopher of language named Gottlob Frege — the distinction between a word or phrase’s sense, and its reference. While “pain” and “C-fibre firings” evoke different images in the mind, they refer to the same type of mental/brain state. In other words, they have different senses, but the same reference. This is still consistent with the view that psychological talk is reduceable to neurological talk, since the reference in both cases would be the same.
The second criticism is far more damning, and comes from another famous philosopher — this time, Hilary Putnam. Putnam’s critique is known as the problem of multiple realizability, in which he argues that, since it’s possible that the same type of mental state could be paired with two different types of brain state, type physicalism is false. Specifically, in standard form, he says:
(1) According to type identity theory, mental state type A if and only if brain state type A;
(2) It is probable, however, that in another species, mental state type A if brain state type B;
(3) Therefore, it probably not the case that: mental state type A if and only if brain state type A.
It seems reasonable to say that a theoretical alien species could have a differently wired, but otherwise functionally identical, brain to ours. What this means is that the necessary relations of identity between brain state types and mental state types are, in fact, only contingent — significantly weakening the position and explanatory power of the theory. For instance, earlier, we talked about Frege’s sense/reference distinction. Because of multiple realizability, it stands to reason that two people could say “I am in a state of pain,” and refer to two completely distinct types of brain state with their words. Different senses and different references mean that they simply aren’t talking about the same neurological phenomenon — a big problem for a view based on the reduction of one set of terms to another.
The final problem we will discuss for type physicalism is that of qualia. “Qualia” is a philosophical term that refers to the qualitative aspects of mental events, and it goes completely unaccounted for in type physicalism. To be specific, qualia are what it is feels like to be experiencing a certain mental event; they are what it is to feel pain, as opposed to just being in pain. They are essentially non-physical and logically private (i.e., unable to be experienced directly by anyone but the subject doing the experiencing at a given time), and so cannot be pointed to during an fMRI scan. Yet, it appears qualia exist — they are part of the everyday experience of being a cognitively functional human being. Unable to account for, or otherwise explain away, qualia, the type physicalist suffers another heavy blow.
Of course, it is possible that qualia don’t exist, and that our intuitions regarding them are false; and though it is disappointing, to truly give that view a fair shake, we’ll have to wait for a later episode all about qualia and phenomenology. For now, it seems a credible criticism, and we’ll leave it at that.
So, what do we think? There certainly are possible responses to the multiple realizability and qualia counterarguments, but most people don’t think they work. A good source to read following on from this overview we’ve done today is the “Identity Theory” article on the Internet Encyclopaedia of Philosophy, especially section 5, “Attempts at Salvaging Type Identity”. I’ll leave a link on the episode transcript page on Medium for anyone who’s interested in that further reading.
In this episode, we’ve learned about type physicalism, substances, qualia, determinism, and why the position of type physicalism is, as it stands, probably false. Next episode, we’ll take a look at token identity theory and its critics, and I’m thinking of doing the first bonus episode between now and then, so subscribe in your podcast app and stay tuned for that.
As always, you can find a link to the Philosophical Investigations Medium collection in the episode description, where you can find a transcript, corrections, and sources for all the episodes so far, and you can leave comments if you’d like as well — I’ll try to answer each one to the best of my ability.
Thanks for listening.
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Bibliography
[1] Schneider, Steven, “Identity Theory”, Internet Encyclopedia of Philosophy, published online. Accessed 2020–08–08. URL = < https://iep.utm.edu/identity/ >
[2] Smart, J. J. C., “The Mind/Brain Identity Theory”, The Stanford Encyclopedia of Philosophy (Spring 2017 Edition), Edward N. Zalta (ed.), URL = < https://plato.stanford.edu/archives/spr2017/entries/mind-identity/ >
[3] Stoljar, Daniel, “Physicalism”, The Stanford Encyclopedia of Philosophy (Winter 2017 Edition), Edward N. Zalta (ed.), URL = < https://plato.stanford.edu/archives/win2017/entries/physicalism/ >
[4] Robinson, Howard, “Substance”, The Stanford Encyclopedia of Philosophy (Spring 2020 Edition), Edward N. Zalta (ed.), URL = < https://plato.stanford.edu/archives/spr2020/entries/substance/ >
