Arguments Against Physicalism | Philosophy of Mind Lecture

[00:00:03]okay good morning so my uh the philosophy of Mind lecture this week this week only is going to be online rather than in person unfortunately I'm terrible with technology so I spent an hour yesterday thinking I was recording it only to find I was actually talking to myself so I thought today the safest thing I can do is just to do something I know definitely works know how to do which is live stream it on my YouTube channel so that's what I'm going to do and then I thought the more I thought about it thought it might be interesting for subscribers to this Channel and students from Durham University to interact perhaps in the comments pioneering some Innovative forms of teaching here at Durham please be polite um okay anyway a one off we'll we'll see how this goes next week we'll be back to being in person and uh um but also next week I'll set aside some time for my students in my office to discuss the lecture material to compensate for the interaction we would usually have in a live lecture um if somebody could yeah we are live okay so so you've had five weeks so far with Professor Gibb going in depth into dualism and the causal closure problem for dualism in many ways this first term on theories of Consciousness you can think of as an attempt to find out which theory has the least worst problem maybe it's a bit like uh Churchill famously said about democracy it's the worst system of government apart from all the others right I sometimes think many people will defend their favored Theory Of Consciousness and say is an absolutely terrible Theory it's got huge problems but it's the problems are less bad than all the others so with du ISM you've got the causal closure problem which you've looked at in great detail we're now going to look at two other theories of Consciousness with me for the second half of the term for the next five weeks physicalism and panchis with physicalism we'll look at the problems posed by the knowledge argument and the zombie argument and now pans psychism when we get onto that presents itself as solving both the causal closure problem of dualism and the um knowledge argument zombie argument problems of physicalism unfortunately it also faces a big problem namely the combination problem so so your job really is to work out what you think of these problems maybe um maybe you think one or more of them aren't really problems or maybe they're all problems but some are less bad than others uh and that can shape how you decide the the you're going to defend in um an essay or the exam at the end of the year okay so so for the next two weeks or so we're going to be looking at these challenges to uh physicalism all right so let's I always like to start I think good philosophy should start with how we're defining words hopefully not end with how we're defining words but we want to get clear on the subject matter so get some clear precise definitions um so physicalism materialism you've already been talking about with Sophie defined as the view that mental properties are either identical with or dependent on physical property so the reductive physicalist position is that my feeling of pain just is identical with a certain pattern of neural firings just as water just is identical with with H2O the non-reductive physicalist rejects that kind of very that kind of very specific identity of a particular feeling with a particular neurophysiological State nonetheless as physicalists they hold that my feelings and my experiences and all of my mental properties are wholly dependent on the patterns of electrochemical activity in my brain but here's a question you might not have considered thus far is well what does the word physical in that definition actually mean it's a funny one it's one of those words that you sort of think you know what it means and then when you stop and uh reflect for a minute it's it's not at all obvious what it does mean it's a little bit like perhaps St Augustine said about time everyone knows what time is until you think about it moment they think what the hell is time so maybe it's a bit like that now there is a huge literature on this which I consider for example in my the second chapter of my academic book consciousness and fundamental reality which you can get on the University system and it's just coming out in paperback actually think it's just come out in paperback um and this is something you might want to dig into in your own independent research um but there's given limited time I don't want to get too bugged down on uh how we Define words so I'm just going to suggest a definition of physicalism the one I work with in U my book Galileo's eror that you're welcome to just adopt unless you'd unless you want to dig into this and maybe uh argue for a different definition of physicalism okay but the definition the default definition we're going to use here is that physical um the physical is defined as what can be captured in the purely quantitative language of physics what do I mean by purely quantitative I mean involving only mathematical and causal Concepts um so since Galileo as I talk about in Galileo's era physics this was Galileo's big decision that physics was going to be well he called natural philosophy what we now call physics was just going to be pretty much a bunch of mathematics um but it's arguably physical science at least more generally is not purely mathematical um in neuroscience and in chemistry we have causal Notions or thing I mean things like mass and charge are defined causally in terms of what they do gravitational attraction resistance to acceleration it's more controversial whether there is causation in fundamental physics but at least there is the notion of a law of Nature and this is a not a mathematical notion it's perhaps a causal notion or or perhaps what we call a gomic or nomological notion we're going to come to this term in very shortly this means to do with laws of nature okay so anyway physics has this quite constrained vocabulary physical science purely quantitative only mathematical and causal concept so we can Define the physical as what can be articulated in those terms and I think that works well actually with the arguments we're going to consider so it's important perhaps to know that these arguments we're about to look at what they're trying to do is that they're trying to argue that the truth of physicalism is incompatible with the reality of Consciousness perhaps in something like the way certain arguments from Evil and suffering against the existence of God try to argue that the existence of evil and suffering or the particular kinds of evil and suffering we find are incompatible with the existence of God God um and because we know that evil and suffering exists we can infer that God does not exist at least that's what happens in the stronger forms of the that argument known as The Logical problem of evil or logical argument from Evil so similarly anti- physicalists are trying to argue that the truth of physicalism is incompatible with the reality of Consciousness we know Consciousness exists therefore physicalism must be false I think it's important to point that out that because these are trying to be arguments from a from a data point they're trying to draw out what they take to be the implications of that data point namely the reality of Consciousness this real arguably real phenomenon we are acquainted with of our own feelings and experiences um now that doesn't mean the arguments work of course many physicalists will reject the first premise maybe some physicalists reject the second premise but it's just to make the point that it's is not supposed to be uh a sort of abstract philosophical argument it's supposed to be an appeal to data and drawing out the implications of um the data point that a certain phenomenon exists okay doesn't mean the argument works but it's important to understand how the argument is attempting to work all right so let's get more into specifics what I'm going to do this lecture is present the knowledge argument and the zombie argument as I formulate them in Galileo's era which is the um course reading for the next couple of weeks um but that is a book aimed at a general audience I hope it's a good introduction to to these arguments and to get you initially thinking about them to shape discussion in your seminar discussion groups um but ultimately we want to get more into the details of the um academic presentation and discussion of these arguments which is hinted at in footnotes in Galileo's era but which is more more fully worked out in for example my academic book consciousness and fundamental reality also in um obviously many many other works by anti- physicalists like David charm as also the response from various physicalists that we will explore so this week we'll look at the more accessible formulation of the argument and then next week we'll dig a bit deeper um if some someone want to quickly comment that that I am live just so I know I'm not talking to myself um okay so let's get more specific let's start with the knowledge argument this is formulated by the Australian philosopher Frank Jackson um who is a wonderful philosopher also a very nice person I had the fortune of uh interacting with him a lot when I was a postdoc at the Australian National University where he works if people don't know what a postdoc is it's if when you finish your PhD before you get a teaching job so if you're lucky enough you can have a job job for a year or two where you um just are able to focus on writing and trying to get some things published um so Frank Jackson uh formulated this argument in the 80s now what is interesting although this is one of the most disgust challenges to physicalism in contemporary philosophy um Jackson actually ultimately changed his mind on it in the 1990s and is now a quite radical kind a physicalist amazingly um so anyway that doesn't mean the argument doesn't work doesn't mean it does work but it's a little interesting tibit uh okay so the nice thing about this argument is that it begins with a story so if you're sitting comfortably I will tell that story it's the tale of black and white Mary um just let me know if we are live if if if someone get gets a chance okay so here's the setup Murray is a Genus neuroscientist she's in fact she's so brilliant her expertise is in color experience and she's so brilliant she knows everything Neuroscience has to teach us about what goes on in the um in the brain when we experience colors so when particular wavelengths of light hit the eyes how they make changes in the brain how that leads to various information processing um and how that ultimately results in certain kinds of behavior she knows all that stuff oh alist boy has just said you're live thank you very much aliser um I'm not talking to myself sorry just so frustrating that I talked to myself for an hour yesterday okay um so so she's this absolute genius and she's got maybe it's said in the future she's got the complete final story Neuroscience has to tell us about the um Neuroscience of color experience but for some reason that is never explained she's raised in a black and white room so Mary has only ever seen black and white and Shades of Gray okay now there are all sorts of issues one might have about the plausibility of this story has Mary never bled and seen her own bled her own blood her own blood um the idea is she's learned physics from a black and white television and black and white books but there are all sorts of understandable troubles my one might have about this this is why I'm one thing I suggesting G's era is actually the St you don't need such a far-fetched story perhaps and I talk about the case of the the late uh Scandinavian color scientist nut noi who had cones missing from his eyes and so was as a result only able to see black and white and Shades of Gray maybe the closest we've had to a uh real life Murray and nut Norby was interested in philosophy in these philosophical discussions so he wrote on what it was like um for him thinking about these questions as something like a real life Mary and you can you can look at that in Galileo's era okay but this this is not the end of the story um the there's a Twist right the climax of the story again it's not explained why but Mary is liberated from her black and white prison the door is flung open and Mary sees let's say on the threshold a bright red rose on the threshold of her prison she escapes into the world around us with all the beautiful colors and has all these wonderful new experiences and then the thought is the thought is of the proponent of this argument not only does she have these new color experiences but as she have has them and in having them she learns something new Mary gains some new knowledge what is that knowledge it's allegedly what it's like to see red what Murray learns is what it's like to see red the thought is despite all she knew about from her brain science and neuros neurophysiological studies that information couldn't teach us what it's like to see red the qualitative character of a red experience this is what she discovers only when she actually experiences color all right right that's the story now I've taught this argument for nearly 20 years now and I've discovered that many people get the argument a bit wrong I don't know whether it's maybe because it's a kind of catchy story and you think oh I get it I get the story um but it's always important in philosophy in this is one of the thing you're being graded on is that you get not just the gist but the details of the argument right I recently debated the um physicist Sean Caroll you can look at that on YouTube also on this channel actually and um I I said to gasp from the audience he wouldn't get a good grade on my course because he'd misunderstood the knowledge argument um but I mean to be fair Sean is um un like certain scientists I won't mention it is pretty clued up on philosophy and has um takes philosophy very seriously but this is actually just a very common issue so what people what people often think is that people often think the argument supposed to be this Mary learned all this neuroscience and yet she still couldn't experience red if materialism were true surely reading the Neuroscience would allow you to experience red now that would be a terrible argument right of course of course not no is not going to experience red uh you know just from Reading Neuroscience you know he's got the cones missing in his eyes but the ability to experience rare depends on what's going on in your brain it's only when Murray leaves the room the light hits her eyes it makes the brain that's when she experienced of course everyone agrees on that right that's that is not the challenge nobody disputes that you know there no reason to think a materialist would be committed to reading Neuroscience lets you experience color you know why would you think that right that that's that's not the argument whether you can experience color depends as everybody agrees on what's going on in your brain that's not the argument this is the argument right the clue is in the title knowledge argument right the point is the claim of proponents of this argument is not just that Mary only has experiences when she leaves the room but that she gains new knowledge new information she learns something new why is that important well because if according to physicalism maybe you dispute this but this is the thought according to physicalism Neuroscience gives you or maybe physical science more generally gives you the complete metaphysical story of what's going on in the brain when you you see color that's it that's the full story that is all the information you can get and so it shouldn't be possible for maray to learn something new Yes she'll have an experience the first time but that shouldn't give her some new information new knowledge because Alle according to physicalism she already had all the information so the analogy I give in Galileo's error is um you know suppose you have suppose you take yourself to have the final theory of black holes well if you've got the final theory of black holes it shouldn't be possible for you to go on and learn some new essential feature of black holes if you do go on and learn some new essential feature of black holes that shows you didn't really have the complete Theory to start off with right similarly if Murray um had the complete story of color experience all the information from the Neuroscience she shouldn't be able to learn any anything new that's the thought she shouldn't be able to learn some new um essential feature of color experiences but the thought is that she does what is the new uh information she learns uh well let's so so let's give the argument in a sort of in premise premise inclusion form so this is the way I lay it out in Galileo's era there might be different ways of laying it out you might want to look at the Stanford encyclopedia entry on the knowledge argument as well is very good okay so premise one oh sorry the slides got a bit messed up by the software there I don't know why that's happened premise one I hope it's still legible if physicalism is true then Mary in her black and white room has a complete and final theory of color experience premise two if Murray in her black and white room has a complete and final theory of coloric experience uh then it isn't possible for her to learn about some new essential features of color experiences she really and yet premise three when Mary leaves her room she does learn some about some new essential feature of color experiences she learns what it's like to see colors conclusion therefore Mary in her black and white room can't have had a complete and final theory of color experiences and physicalism is false okay so lots of good responses to this argument I'm going to be exploring but make sure if you're discussing it in an essay you present the argument correctly uh not just the gist but the details um so what is this so so the basic idea according to Frank Jackson when he was in his duelist phase presenting this argument he thought there is this this feature of reality that you can't can't learn about from Neuroscience from physical science and is therefore non-physical what is that feature of reality it is namely the qualitative character of experience of color experiences in this case but then he would generalize out to the the quality the qualities we find in pain experiences or pleasure experiences or any kind of feeling or experience Jackson thought these qualities are are non-physical because they go beyond what physical science talks about now Jackson wasn't um a substance jewelist in the sense of deart he thought there were just bodies and brains he didn't believe in a non-physical Soul or substance but he thought some physical entities particular in particular brains as well as their physical properties the kind of neurophysiological properties Physical science deals with and patterns of neural firings and so on physical science uh sorry sorry brains also have these non-physical qualities or qualia the qualities we we encounter in color experiences or any kind of feelings and experiences and it's these he thinks Mary learns about or or the color versions of those when she leaves their black and white room it's those that physical science couldn't teach us about and um and that Murray learns about okay right well I'll leave the knowledge argument there for now um uh well some comments coming up here that may preempt where we're going to go with this uh but for this week I think I'll just uh for the moment plot on with the lecture so let's move on to the zombie argument um so first things first right important to start off with how we're defining words zombie is a technical term in philosophy we're not talking about uh Hollywood zombies we're talking about philosophical zombies which are defined differently so would zombies as we all know look like this and this and this whereas philosophical zombies look like this and this and this in other words they look just like you or I not only do they look like ordinary people but they walk and talk and behave in all ways just like Ordinary People and the reason they do is because the physical workings of their bodies and their brains are just like that of a normal human being of a real human being but there's a crucial difference a zombie is not conscious there's nothing that it's like to be a zombie so you stick a knife in a zombie they'll scream and run away but they don't actually feel pain if the zombies crossing the road they'll stop look carefully both ways carefully cross the road but they don't actually have any visual or auditory experience of the world around them the lights are on but nobody's home okay so the definition of a physical of a philosophical zombie is it's a physical duplicate of a human being but which has no conscious feelings or experiences now you might think why are we talking about this nonsense first thing to note is nobody thinks zombies are real like that's not the point of I I think there is one philosopher who thinks everyone is a zombie but them somebody was another philosopher was pressing this these arguments on me in a bar recently that try to show that we should all think everyone else is zombies and not just the skeptical arguments but anyway in general philosophers aren't saying these things really exist in the first instance the interest is that they seem to be logically possible in the sense that there's no contradiction or incoherence in the idea of a philosophical zombie so the word that's often Ed here in the literature is conceivability I hate that word because it always makes everyone think of it's just about what what you can imagine and that might be tied you know to contingent facts about human psychology but that's not really what what what is what is what we're after here it's it's more a notion of logical coherence what you could what couldn't be ruled out just through reasoning a priori um so I I prefer to use the word logical possibility although you need to be aware the word conceivability is used a lot in in the literature I mean of course there are there may be slightly different definitions of logical possibility maybe Sarah uan teaching logic would pull me up on this sometimes it's used to mean something a little bit more um narrow what can be ruled out in a sort of formal logical system I'm using it a bit broader than that just to mean what can be ruled out through reasoning um so really what we're thinking of is so contrast flying pigs and square circles neither of these things exist um but flying pigs have a slight advantage in that they there's no contradiction or incoherence in the idea of a flying pig you can't rule out a flying pig just through reasoning sitting in your armchair you have to go out and look at the world to know there are no flying pigs at least on our planet in contrast Square circles are just logically incoherent the very idea involves a contradiction and so you can know just by sitting in your armchair startling fact as I discuss in Galileo's era you can know that nowhere in the whole universe all of space and time are there any Square circles because they're just flatly incoherent crucially also we're talking not about um what at first glance you might be able to rule out but what could be ruled out in principle by A Perfect Reasoner as as it were so David Charmers distinguishes Prima fasi conceivability from ideal conceivability so primer conceivability is what you can rule out very quickly maybe Square circles are a bit like this 2 plus two being five but uh maybe time travel is primacia conceivability or or time travel involving changing the past many philosophers think time travel stories that involve changing the past at least unless you have hyper time or parallel universes or something these are contradictory and yet they you know they seem to make sense at first we can watch Back to the Future where Marty McFly changes the past kind of seems to make sense um but many philosophers would say when you really think about it it it it turns out to be contradictory really what we're interested in is ideal conceivability what you think unlimited reasoning could rule out maybe you think there's something dodgy about the notion of Ideal thinking about the ideal reason when there are no such beings you could look at David charma's long paper does conceivability entail possibility but in any case that's what we're after we're thinking are zombies more like flying pigs or more like Square circles are they the kind of thing you can rule out just by reasoning because they have some kind of subtle or UNS subtle contrad ition all right so building on this and just further clarifying this it's important to distinguish different kinds of possibility uh one important distinction is between logical and nomological possibility as I said earlier nomological means to do with the laws of nature so nomological possibility is what we can rule out is what is inconsistent sorry well if we're talking about possibility what is consistent with the laws of nature so maybe maybe maybe um flying pigs are nomologically impossible because of because of the strength of gravity in our universe because of the mass of pigs maybe flying pigs are impossible um you know that's disputable I'm not I'm just sort of trying to illustrate the point um but certainly it would seem that they're logically possible in this more General sense that there's no contradiction and so in another possible Universe if if the laws of nature had been different it seems there could have been flying pics maybe traveling faster than light is nomologically impossible perhaps not not obvious some people think there could be tachon these hypothetical particles that travel faster than life like but maybe some physicists think it's nomologically impossible the laws of nature don't allow it but it seems to be logically possible there are non-contradictory universes it seems that uh have faster than light travel all of this I'm sure can be disputed but I hope you get the the idea here so this is an important distinction in Galileo's era I I suggest that the neuroscientist annel Seth who I've uh debated a few times um you can find on YouTube um we debated in we did the the last year's annual Royal Institute of philosophy debate with two other philosophers um I suggest that he in his discussion of zombies he mixes up logical and neological possibility you can have a look at that because so David Chamas is the perhaps well-known and influential defender of the possibility of zombies but he he doesn't think they're nomologically possible and that's because David Chas believes in what he calls psychophysical laws of nature he thinks that in our universe there are these special fundamental laws of nature over and above the laws of physics that ensure that certain physical States produce Consciousness so charmis thinks if we were in a purely physical world if physicalism were true if there was just matter and the laws of physics then we'd all be zombies there wouldn't be any Consciousness but fortunately thanks Charmers there are these extra laws of nature in our universe that bridge the gap to Consciousness and that ensure that when you get certain specific neurophysiological happenings in brains Consciousness pops up and he thinks it's a it's a task of science partly through doing Neuroscience to try and work out what the what the psychophysical laws are so although Charmers is a duelist he calls himself a a psycho sorry a naturalistic duelist in that he thinks Consciousness is not physical but he hopes we can spand the project of Science and bring non-physical Consciousness into the story of science understand non-physical Consciousness as a lawg phenomenon so we can relate this back to what Frank Jackson believed in his du list days uh these non-physical properties that um he thinks brains have that Murray encounters when she leaves her room I mean she knew some of them already but the the the color ones that she didn't know about she couldn't work out from new science that she encountered you might wondered well where did they pop up from well Charmers would explain that in terms of the psychophysical laws it's because of the psychophysical laws that brains develop these non-physical properties okay um all right so this is the first question are zombies um logically possible now a lot of people have the initial reaction I said they're just ridiculous they're abs of course they're not possible they just seem absurd might be worth noting um just as a matter of sociological fact 60% of anglophone philosophers in the recent 2020 Phil paper survey on the Consciousness question 60% thought they think that zombies are logically possible uh quite a consensus philosophers who normally disagree on everything only about 16.4% I think think zombies are logically impossible inconceivable um now this is not a popularity contest and you're very welcome many good philosophers do think zombies are logically impossible and you're welcome to defend that but it might at least give one a little bit of pause of for if 60% of the relevant experts who've sort of read all the literature had their views scrutinized by peer review and in talks and so on um I've reached that view okay but what I do in Galileo's era I try to give a little argument for The Logical possibility of zombies and we'll briefly consider that now and this argument is rooted in the problem of other Minds this skeptical worry that it seems whatever empirical information we could learn about another human being or another animal it wouldn't prove that they were conscious in the sense of logically demonstrating it right if you think about everything you could learn about my brain and all the electrochemical signaling and so on doesn't seem that any of that proves that I have feelings and experiences all of that seems consistent with the absence of feelings and experiences and the possibility that I'm just a complicated unfeeling mechanism M um this is this relates to challenges in thinking about animal ethics we used to think fish were not conscious most that used to be the majority opinion I think it's now the majority opinion that they are conscious but it's very hard it's hard to see what we could learn about the workings of the bodies and brains of fish that would conclusively demonstrate whether or not they have feelings and subjective experiences um now I'm not saying there aren't ways to rationally proceed here I guess we if it's a human being you can ask them what they're feeling you can scan their brain uh you can try and correlate in that way conscious experiences with brain activity and you can extrapolate to the uh non-human case my point is here just that arguably you may disagree with this but on the face of it it seems that um not nothing we could learn empirically would logic ically demonstrate and in that strong sense prove that um that the person has feelings and experiences you might say okay well why am I why am I working with this very this that seems a very strong demand logically demonstrating it not many things are logically demonstrated well the point is in this context it seems that if zombies were logically impossible it would seem you could demonstrate that others were not zombies because you could um you could there would be certain empirical facts about the human that would logically entail that they have Consciousness okay so so it seems and here's the premise one here if zombies were logically impossible it would be able to prove that you're not a zombie if you share the intuition and you may not that you can't ever conclusively prove that someone else is not a zombie that then it does seem to that we can infer that zombies are logically impossible okay well there's a quick argument you can consider um okay but you may still be thinking all right zombies uh who cares maybe zombies are logically Poss loads of things are logically possible flying pigs golden mountains whatever me being King of the universe who cares what's logically possible we should be interested in the real world well one way of you know how how you might how could this m logical possibility rule out um a popular scientif a popular philosophical option such as physicalism well one way of trying to work this mere logical possibility if it is a logical possibility into an argument against physicalism appeals to what we can call the identity principle this principle that if X and Y are identical then it is logically impossible for X to exist without y or vice versa it's maybe important to clarify what we're meaning by logical possibility here sorry I I didn't mean to say that it may be important to clarify what we're meaning by identity here what we're meaning is what is sometimes more specifically called numerical identity where X and Y are one and the same thing so take the example of Superman and Clark Kent Superman is identical with Clark Kent in the sense that there aren't two people there's just one person with two labels one person that sometimes flies around with a cape and sometimes wears glasses and works as a reporter for the Daily Planet but that's just the same person right unbeknownst to many people but that's the reality so because it's just one person um well anyway got on that so this contrasts with for example qualitative identity in for example when you have when we talk of identical twins it's not that Bill and Ben the identical twins are the same person it's just that they're perfectly resembling of course they're never perfectly resembling we could imagine clones or we to get more sci-fi you could have um you know mirror universes where everything on one side of the universe perfectly mirrors what happens on the other side of the universe uh so then you would have perfect resemblance or qualitative identity perhaps but that's different to numerical identity where you've just no it's just one person with two labels or water being identical with H2O right it's not that like I've got a bottle of water here it's not like there's the water in the glass and the H2O no water just is H2O one there's one kind of stuff with two names one is the sort of the everyday name for it and one is the more scientifically revealing name but it's just two terms for the same thing so the thought behind the identity principle is well look in these cases where you've just got one thing with two labels well obviously X and Y couldn't exist independently not even God could tear apart Clark Ken from Superman CU Clark Ken just is Superman there are two people to tear apart now there are possible universes where um that one person doesn't fly around with a cape there are possible universes where that one person doesn't wear glasses and work for the Daily Planet but that's that's not arguably that's not a possible world where Clark Kent isn't Superman because Clark Kent just is Superman that's a possible world where this one person who we refer to in these two ways behaves differently has different properties similarly not even God you might think could tear apart the water in this bottle from the H2O because water just is H2O um there aren't two things to tear apart um there's no possible Universe where water exists without H2O so this is the thought if X and Y are identical then it's logically impossible for one to exist without the other and with this in place we get to the formulation of the zombie argument slightly simplified we'll get more into the details next week that I present but this is the C simplii present that I simplify for I present in Galileo's era um so actually what I don't say in Galileo's era is that again I'm not trying not to over complicate uh a general audience but I'm actually just talking about what we've come to know is reductive physicalism that involves a specific identity between feelings and brain States so let's make that implicit assumption um Let's Make That explicit assumption implicit assumption explicit now and here's the argument so if reductive physicalism is true then feelings are identical with brain States if feelings are identical with brain States then it's not logically possible for feelings to exist without brain States or vice versa that's follows from the identity principle um if zombies are logically possible then it is logically possible for brain states to exist without without Feelings by definition of a zombie that's just what a zombie is um a zombie has all of the brain States a human being has but none of the feelings right that's just what a zombie is so when a you stick a knife in a zombie it has the brain States a human has when they feel pain but it doesn't actually feel pain therefore if zombies are logically impossible so sorry is that logically possible physicalism is false zombies are logically possible we could support that with the earlier slide therefore reductive physicalism is false okay so this is just an argument against reductive physicalism we can um digital gnosis is uh really again some people in the comments in the same way I can conceive of brains not being phenomenal States epistemically similarly I can do the same thing with water and H2O my imagination is not a guide to anything useful well this perhaps preempts uh the the deeper discussion of this we're going to get into next week um um also well just a slight qualification on that again this is not about imagination right this is maybe we're misled by this word conceivability what we're talking about here is not what human beings can imagine but what any possible reason ideal reasoners the perfect reasoners could rule out just through reasoning so that's not limited to contingent human psychology now you might well think this is a dodgy notion of the ideal Reasoner that's something one could pursue but just to be clear about that but yes there are um ways we could uh further Challenge and lead into a a a more Nuance form of this argument but um okay we just I make one one one more Point here so as I said this is aimed only at reductive physicalism but actually it's quite easy to expand it I think to more General forms of physicalism so what about non-reductive physicalists who think mental properties are not specifically identical with specific neurophysiological properties but are just are dependent on physical properties are dependent on what's going on in my brain well whilst non-reductive physicalists don't ident identify mental properties with physical properties specific neurophysiological properties most of them I I would say perhaps all of them in my almost all of them at least in my experience you may find some exceptions do do identify mental properties with functional properties of some kind what are functional properties okay very important word functional here functional properties are defi are properties that are defined in terms of behavior both external Behavior sensory inputs and behavioral outputs but also internal Behavior Uh behavior of the parts inside of the brain and behavior dispositions how things are disposed to behave um we might say for example the the V is dispo it's fragile in the sense that it's disposed to break uh even if it never breaks in its whole existence we can still talk about how it's disposed to behave so I mean historically um people started off thinking about behaviorism if we could Define mental States just in terms of outwards Behavior inputs and outputs defining pain in terms of you know getting stabbed and screaming people quickly realize that that's too simplistic we need we need to talk about internal Behavior as well as external behavior and about behavioral dispositions dispositions to behave as well as just actual Behavior but still and this leads to the position known as functionalism rather than behaviorism which is still trying to Define mental States purely in behavioral terms but it's this more nuanced sense of behavior both internal and external both dispositional as well as explicit actual Behavior um so most physicalists um who are not reductive physicalists are functionalists in some very general sense so we can simply say um so even if they don't identify so non- rtiv are not going to identify mental states with physical States but they are likely to identify them with functional properties and therefore we can just slightly modify the argument so that it's aimed at physicalism more generally if physicalism is true then feelings are ident sorry that should be are identical not and identical are identical with brain States or functional properties if feelings are identical with brain States sorry that should say or functional properties SL functional properties then it's not logically possible for feelings to exist without brain State functional Properties or vice versa again follows from the uh identity principle uh if zombies are logically possible then it's logically sorry if zombies it's logically possible POS for brain State functional properties to exist without feelings therefore if zombies are logically possible physicalism is false uh zombies are logically possible therefore physical is false okay so that's the initial introduction to the argument next week um we will delve more deeply into um challenges to this argument which leads to the more nuanced form that you actually find in the academic literature defended for example by me in consciousness of fundamental reality or David Charmers for example in his paper the two-dimensional argument against materialism and of course the responses the Contemporary physicalists give to that but hopefully that should be enough to uh get you going on discussing your initial thoughts on these arguments and I will arrange for some time to interact on this next week um also if you are subscribed premium subscribers to the channel to the Mind chat Community uh there will be a dis hour some point to discuss this um or anything else later this month I'm in discussion with those people um thank you for listening whoever you are maybe students and subscribers would like to interact in the comments please be polite um I wonder how this will go this you can all praise me in the feedback for my pioneering teaching methods okay um well I'll leave it there for now and I will see you in person next week thank you very much for listening bye-bye how do I stop this