Descartes 2: A Priori Knowledge and Mind/Body Dualism

okay welcome to this second installment of the lecture on rene descartes so I want to begin this lecture talking about a very famous argument that Descartes presents known as the wax argument before we do that it might just be useful to take a second to remind ourselves what we talked about in the previous lecture so we went through des cartes method of doubt whereby he doubts that the senses are accurate he doubts that the physical world exists at all he doubts that the truths of mathematics are what we think that they are until he finally gets to the point where he knows there's one thing which is undoubtable which is that when he is thinking he is doubting we also looked at the arguments for Descartes view that thinking is what we would call very generally in our contemporary times experiencing so feeling pain is thinking tasting chocolate is thinking as well as the more traditional things that we would think of as having thoughts all of these things which occur in our mental stream of consciousness are thinking for Descartes so he knows that that is his essential characteristic so now what do we know about the physical world that's the next step remember with his what he wants to do is build a bridge back what he's got is that he exists as a thinking thing he's got clear and distinct ideas and now he wants to see what he can build back so to begin this argument let's consider some piece of wax it's got certain properties like for instance it has a taste a smell it makes a sound if you were to tap on it and it's got a certain shape so in the meditations Descartes says consider that this piece of wax comes fresh from the honeycomb and so it's got these physical properties and if you ask someone what they knew about the wax some someone who was before they engaged in this sort of philosophical reflection you said what do you know about this piece of wax you might be tempted to list off this range of properties right it's also sorry got a bit of hardness too but of course Day cards point here is that if you take this piece of wax and hold it next to the fire and it starts to melt then every single one of these physical properties begins to change it's no longer got the same smell it's no longer got the same shape it's no longer about the same size no longer has the same field or taste etc so whereas before it used to be hard now it's this puddle whereas before it smelt like honey now it smells completely different so every one of these properties changes so if we just examine what's in our sensory experience well at one moment were presented with this group of properties and at the next moment we have a different group of properties and that's every single one of its properties changes but Descartes wants to emphasize this point we seem to know that it's the same wax throughout this process but of course there's nothing we can point to that's physically the same every one of its perceptible properties has now changed it's the same it's not as though we somehow think it's the same wax before and after excuse me it's not as though we somehow think it's different substance before and after its melting we keep the idea that the underlying stuff has remained the same even though every one of its surface properties has changed but of course the real question is how do we know that how do we know that the wax is the same wax before and after it's melted and the cards point is that we can't know it by looking at anything where that means simply by sensing it because everything that we would sense is now different so we must know the real nature of the wax by intuition and what do we now know about the wax well by thinking by using reason we understand that the nature of the wax is an extended substance which possesses these various properties and we can't really come to see the substance but we know it must be there because it's the thing which is causing our experience and in which these properties are in so what we have then Descartes concludes from this is some appearances we see the wax the way that it looks it presents to us an appearance on the basis of those appearances we make a judgment that there is a physical object out there and we now know that the essential attribute of this physical object is that it's extended in space and can take different shapes but strictly speaking we don't have any contact with that object what we see are its appearance is the way it presents itself to us in our experience so we perceive the real nature of the wax as an extended substance solely with the mind and this is again Descartes way of trying to arrive at the conclusion that we spoke about earlier so notice there's in this his representational Theory namely that what we have are the representations of some substance outside of the mind and these are the appearances and we also have his view that the essential attribute of physical objects is being extended in space that's what it means to be physical for Descartes but it's somehow occupying some area of space and physical objects are exactly those things which can occupy various areas of space and which can be changed to occupy other areas of space but what remains the same there is that there's occupiers of space ok so we can sum all this up then putting the last lecture together with this brief run-through of the wax argument so the first thing is that Descartes is a duelist so we think there are two fundamentally distinct elements to reality and the first element of reality is the mind and the mind exists for Descartes as a non-physical entity whose essential characteristic is thinking now why would you think this well Descartes is led to believe this actually by the method of doubt where there he was looking for something which can be known but along the way look what happened so Descartes says it's possible that I could exist even without my body so that's exactly the scenario we ended up with in the method of doubt there we went through a process where we were considering well how can I tell that this isn't some dreamlike scenario where nothing physical really exists at all just my consciousness just my mind and I'm being deceived by some supremely powerful evil demon so there certainly seems as though I could exist even in the absence of anything physical but if that were the case then my mind can't be something which is physical so Descartes says it's conceivable that this is happening we couldn't rule it out previously right for all we knew it was happening right then so it's got to be possible that that's happening and if that's possible the mind and the body are not the same thing because when things are really the same they can't be separated that way right you can't imagine the the three sidedness of a triangle existing somehow independently of the triangle itself so that's supposed to be clear and distinct and so true and of course Descartes has another reason for thinking that the mind is non-physical which he thinks if did you know if this one wasn't good enough we should have already known because minds don't seem to be the kind of things that have locations they don't seem to be extended in space and physical things by their very nature are extended in space and can be given locations and the mind doesn't seem to have any of those properties right so now the other end of this dualism is the physical nature of the world outside the mind physical objects by definition never think so the body plays no role in thinking Descartes believes the brain certainly isn't a thinking thing it's where the mechanism of the body is connected to the mind in some way or the way they communicate one with the other but they are distinct things so physical objects have their characteristic as extension which means that they are extended in space they occupy an area space and they never think and mental things are unexpended they're not located in space or time and they are essentially thinking things now this is supposed to be what the wax argument led us to just a second ago by going through this process of examining the wax carefully and asking ourselves what we really know about it we saw that the sensory perceptions we had a bit were sort of confused none of them demonstrated the real nature of the wax we know that because all of those things could change and the wax remain the same so those things can't be essential attributes of the wax what we discovered was that the wax essentially is just an extended substance occupying space time and we know that not by seeing anything but by thinking about the nature of the wax on so on the one hand then we have these extended non-thinking substances which exist in the world and are governed by the mechanical laws of physics which Descartes is interested in discovering and on the other hand we have mines which are unexpended substances they don't exist in space and time they are not governed by the laws of mechanical physics they have a different realm where thinking and experience happened so that's de cartes view about the world and our place in it and this is important too so I'll re emphasize it but that de car really is suggesting here that what you are what you really are is an immaterial mind what you interact with our ideas and this is des cartes use of the word idea to mean experience or anything that's mental whatever so that when you're walking around in your normal day-to-day life and you think that you are encountering physical objects Descartes says that's not the case really what you're encountering are representations of physical objects which you're using to navigate your mechanical body around in a physical world now the procession of these ideas so the stream of the these ideas in your mind makes up your mental life and that's exactly what's happening to you right now you're hearing these words or sitting at a desk perhaps you're on a subway listening to this lecture wherever you are there are experiences which are happening and that's the kind of exactly what your mental life consists of and this is why people have coined the term the Cartesian theater because on des cartes view our normal everyday experiences are much like a theater we the conscious self the person are somehow observing the stream of experiences and we are passively observing them much like a viewer in a theatre now Descartes thinks that we have immediate and unfailing access to the happenings within our own mind so that all we need do is focus pay attention see what's going on and there's a bit of infallibility there by what she means that it's impossible for us to be wrong about our own experience so we may be wrong that there's a table in front of us because we may for instance be dreaming and we can't rule that out a priori although we'll eventually try to get to the point where we can rule it out but where we are now we can't rule out that this is all one big dream being fed to us by some very malevolent creature who's bent on deceiving us but even if that were the case when I seem to myself to see a red table in front of me I can't be wrong that it seems to me that there's a red table there I might be wrong that there's a writ there is a red table there but what I can't be wrong about is how it appears to me the way the experience is for me to have it this is a very interesting view that Descartes has that makes us experts so not only are we infallible but we're also incorrigible nobody could be in a position that tell us that we were wrong and this again was important if you remember from the phantom limb pain argument for representational ism Descartes there says look he relies on this premise in that these people when they sincerely say that they're in pain we can't even fathom that they're wrong if they really believe that they're in pain then there's no sense in which that belief could be mistaken or no sense in which we could be better more reliable judges of whether they really are in pain so the only thing we need to establish is that they're not lying that it's sincere and therefore we immediately know that they cannot be wrong and so that that's real pain and that was an important step in his argument because if these people could be wrong then we might say well you know how do you know you're in pain you just think you're in pain it only seems to you as though you're in pain and Descartes denies this there's no sense in which you could be wrong about the nature of your own experience there's no sense in which someone else could be in a better position to know what you're feeling then you are that's a crucial premise in de cartes argument here so now the question for Descartes is whether or not these experiences accurately represent reality right so you're sitting in there in this Cartesian theatre so to speak and you're observing the experience of a table the big question for Descartes is how do you know that that experience of a table is accurate in the sense that it correctly captures the way things are outside of the mind so how do you know your representations are to use a fancy term veridical that is track the nature of reality so what I want to do here is just compare two views and we'll use some basic pictures so here's the common-sense view about the relationship of human beings to the physical world this is certainly some like Aristotle's view probably the view that most of the ancient Greeks had so there you are over there on the left and there's the the world out there represented by a tree so the tree is green the tree has brown bark and when you observe the tree when you observe it you are in direct contact with the tree and you have access to the real properties that the tree itself Pass so the greenness of the tree is a property of the leaves of the tree they are green and you can get a feel for this what this means when we say a kind of direct realism where you're directly in contact with the objects by trying to ask yourself well what would you say about a case where the tree was in the dark so at night let's say on a moonless night when there are clouds above so no stars no artificial light the tree is out there and it's pitch black and you want to know is the tree still green well the common sense picture has it that yes the tree actually is still green because the greenness of the tree is a property of the thing itself and just like when you put a square in the dark it doesn't cease to be square because the thing is square so it's going to be square whether or not anyone can see it or whether or not there's any light around so to the common sense picture has it that the tree is and its colors are that way whether or not anyone is around whether or not it's light or bright the tree has these properties and the revealed to us somehow directly in sensation and Aristotle would have put this in terms of the form of the color green entering the mind in the mind somehow becoming like it and there's a big dispute about what that exactly means but it's pretty clear that ever thought Aristotle thought that the mind was able to take in these forms and so you really were directly in contact with the green itself which was a property of that object now des cartes picture is very different so on the one hand you have the physical world which according to Descartes lacks properties like color sound etc the physical world is composed of those properties which can be mathematize which means that you can quantify so you can say how many feet how many decibels etc sound waves etc exist and these things are extended in space but don't have any of the properties that we would normally associate with them those things causally interact with the body which is itself a kind of mechanism the body then produces in the mind the conscious experience which actually does possess properties like color and so on so this is what we'll find out a bit later corresponds to Locke's distinction between primary and secondary qualities if you've heard of that distinction it also corresponds to the pre-socratic adam is view of the distinction between bastard and legitimate properties and descartes really never gets the proper kind of credit for having this kind of view but he really does the the things that we think of as color sounds taste etcetera exist in the mind only and don't exist out there now on the basis of these experiences we make a judgment about the cause of that experience so we take hard things go through something of a process as follows we are having a conscious experience as of a tree what would be the best explanation for that experience well clearly the best explanation is that there's some object out there which is producing this very experience so we make the judgment that the tree in the physical world is the causally responsible thing for our experience of the tree so that's a much more complex picture and notice the little thought bubble thing is supposed to be the non-physical mind that's really you not the body down there so there's a difference between the Meccan mechanical body and the non-physical unexpended mind and so you shouldn't be identifying yourself with a smileyface thing down there that's just the body the real you is this non-physical thing in which the experiences occur so this is a very different kind of view than the common sense picture it's no longer the case that you have direct access to the objects themselves because your thought bubble see you're removed from the physical world in that you really are a non-physical thing you're not in the physical world not in the sense that physical objects are you're not in the physical world in the sense that your body is the body is a mechanism so sometimes I like to use an analogy at this point and it's not the greatest analogy there are flaws with it and Descartes probably wouldn't be happy with it but we can sort of I think it gives us a intuitive grip on what's going on here and we'll modify it as we need to so think of for instance the way that NASA sends Rovers to other planets so as I'm recording this in the United States has recently had a rover on Mars and the rover is basically a really fancy remote-control car equipped with all kinds of sensors and cameras and etc and we send the rover there the rover goes to Mars on a on a ship it is dropped there and then once it gets there we can send it signals and drive it around the thing is sending signals back to us and producing on a screen in say Fort Lauderdale at the NASA headquarters images of Mars and based on those images you the scientists can drive the car around so they say ah there's a rock off in the distance head over towards that rock and they can point the rover in the direction of that rock and they can scoop up samples and etc etc now of course the scientists are not really on Mars they are not interacting with Mars in any real direct sense they're in a room in Fort Lauderdale what they have access to our images on a screen which are being sent back from Mars now using those images they're able to navigate a mechanical object around on the surface of Mars and the mechanical object really is on the surface of Mars and based on these images we can really navigate this thing around that environment now this is something like the picture that Descartes has with respect to the mind in the body so the mind would be the scientists in their control room seeing the images having access the controls and the body would be like the Martian Rover it's not in the same place as the mind and everything that the mental stuff is doing depends on the body being really in this environment and this is where the problem of the evil genius comes in because here we are trapped in the mind we're having these experiences we're trying to make a judgment about whether or not these experiences are in fact correct whether they really really do represent the world outside of us there may be no world at all if the evil genius has his way then this is the way things are the world just isn't there all there is is the consciousness we have an experience of a tree it's the evil genius who causes that experience of a tree in us it's not caused by some external tree we have experiences as of other people they aren't really there they're just figments put their non-player characters created by the evil genius so that's the problem that Descartes has got himself into by he's painting himself into a corner so to speak where the corner is the mind he's saying look all I really know for sure is that I exist that I have thoughts that I have experiences and as far as I know at this point everything else could be fake everything else could be the product of the evil genius okay so the question is how do we get out of this hole we've dug for ourselves and I like to try to think of this by in terms of an analogy and it's similar to the Martian Rover analogy so now imagine that you've been raised in a room so you've never been allowed to leave this room you've just you were born in this room you've never been outside of the room you'll never go outside of the room as far as you know there's no doors there's no entry there's no exit it's a sealed system in this room you have a television monitor that shows you scenes from the outside and usually I'm giving this lecture at LaGuardia so I have been damn Street there which is where LaGuardia is located but just ignore that you're seeing scenes from the outside world or if you like in - the Martian Rover you're seeing scenes from Mars so based on these images you conclude that there are people out there doing various things but of course the analogous question here is how do you know that the camera is really out on the street or how do you know that the Martian Rover is really on Mars it could be the case that someone wants you to think that there are people out there who are doing various things but in reality it's just some kind of mock set it might even if you want to take this to the furthest extreme simply be some very very very well done computer simulation so you're seeing all these things on the screen maybe it's not even as Hollywood said it's just a intricate computer simulation so you're trapped in the room you can't get out all you have as evidence is the images on the screen that's the analogy for the mind and the position that we're in we can't leave the room and go outside right there's no way for you to check to say ah here's an image of a person walking down the street here's the real person it's just off limits well how could we know well Descartes argues that if God existed then we would have some evidence some reason to believe that these images are correct now why well first of all God is by definition completely moral according to Descartes so there's no way that God could even possibly be immoral he's supremely good well if that were the case and if God existed then we would know that our experiences were for the most part accurate and trustworthy because if they weren't God would be a deceiver so here we are we're in this position how do we know there's no evil genius out there well if we can prove that God exists get rid of David Bowie and replace him with God from the Sistine Chapel if we knew that God was out there then we would have to believe that the way our senses to pick the world is the way they really are if they weren't God would be a deceiver and Descartes just denies that God could be a deceiver it's not possible for God to practice deception on Descartes view okay so then how can we tell the difference between these two competing hypotheses about the origins of our experiences on the one hand we have a hypothesis that there's some trickster out there who's feeding us this stuff and we'll knit so our experience is radically wrong on the other hand we have the hypothesis that there's a benevolent being out there who guarantees that the picture is set up right right so that even though we're locked in the room we have the highest most trustworthy source well Descartes proposes to go through the various ways that ideas or experiences could be produced in us and try to see what's what's here so there are only really three possibilities here so some of our ideas may be caused by physical objects some of our ideas may be caused by ourselves so for instance my idea of a purple vampiric unicorn is something that I made up that unicorns are cute and fluffy vampires are bloodthirsty and so wouldn't it be hilarious if those two things were joined into a new creature a vampiric unicorn which is purple like my little pony all right so I created that idea in that image which I'm picturing in my mind or the third possibility that Descartes thinks is that the ideas may be innate which is meaning to say that they're born in with us that when the mind is born these ideas are there already in much the same way that if you buy a computer it may have you know Microsoft Word pre-installed on it it already just quote-unquote knows how to process words okay so these are the three options I'm looking at a table it might be the case that there's a table out there which really produces my experience at the table it may be the case that the table is the experience has produced in me like when I'm having a dream and I'm the source of that or it may be an 8 in there already now at this stage and the method we can't just say hello it's physical objects because that's what we're trying to prove so we cannot say ah well you know these things are produced in the mind by physical objects that's ruled out so that leaves us the only other two so either they're generated in us or the ideas are innate ok so Descartes at this point proceeds to make the argument that every clear and distinct idea is an innate idea it's so he believes that like Plato all of logic rationality and those kinds of things are born in us how do you make these this argument how do you make this claim well here's Descartes spew most of my ideas I could have made up myself like people dragons angels fire that could all be stuff produced in me in my experience of a dream but here's one special concept was Descartes wants to focus on and this is the concept of God the idea of a perfect being could I have been the source of that idea well the concept of a perfect being is a concept of an infinite being right one that has unlimited power unlimited love unlimited knowledge there's no limits to God but if that's right then the question is could I myself have been the source of this idea of the oven infinite being Descartes answer is no I couldn't have been the source myself well why not well he appeals to a principle which would have been well known from the scholastic period going back to Aristotle which is that an idea must be as real as the effect otherwise you would have get something from nothing so this is a clear indistinct idea that whatever is produced in an effect must have already been contained in some way in the cause and here you can see card again employing a notion which is similar to Aristotle's so earlier in the wax argument we saw him employing this substance attribute distinction which is very Aristotelian and appealing to the idea that in the course of a change the wax melting in this case there's got to be something which remains the same the material cause this is something knowable by reason the material cause of course for Descartes turns out to just be something extended in space so he does differ with Aristotle but it's very Aristotelian in its underpinnings and the same is true here so Aristotle argued that the formal cause must have been contained in the efficient cause already in order to transmit it into the material cause so that for instance when a fire is heating up a pan as was one of our examples the fire must already have the form of heat that's how it's able to transmit the heat into the pan so Descartes appealing to something like that here when you have a cause and in effect the cause must contain within it somehow the needed stuff which is going to end up in the effects otherwise you would have got something from nothing right there would have been more in the effect than was in the cause and that just seems contradictory well if that's the case Descartes then goes on to argue well here the effect is my idea of God and remember the effect is therefore infinite because it's the idea of an infinite being but if that's right then only something which was itself infinite could have been the source of that idea there's no way that I myself a finite being could come up with this idea since that would be getting more from the source so I'm not infinite I'm finite so you'd have more in the effect then was in the source already so there I can't be the creator of this so we can infer then that the only thing which could have created my idea of god is itself God an infinite being so therefore God must exist otherwise I would have no explenation for how I could even have the concept of God so this is a very interesting argument a lot of people are not convinced by it and we'll see Hume has an interesting rejoinder to this on where the so what the source of our concept of infinity might have been so we'll turn to that when we get to Hume for now just suffice it to say that Descartes is convinced by this he thinks yeah this is pretty good this shows that God must exist as the cause of my concept of God and I know that God isn't a deceiver so now I've closed the circle now I've accomplished what I wanted to do right so now I know about the physical world because I know that God wouldn't deceive me but the knowledge that I have consists in these innate a priori clear indistinct truths so what I know about the physical world is the stuff that math geometry physics logic and philosophy tell me about the physical world I know that it exists as a mechanism as an extended substance in space which conforms to the laws of physics so that I know that F equals MA is true and that F equals MA correctly describes the way the substance is outside of the mind behave now the information from our senses is what Descartes calls obscure and confused the real knowledge we have with the physical world is this a priori knowledge so he's he's done what he wanted to do he's showing that look we know how the physical world behaves but we know how the physical world behaves on the basis of logic and mathematical physics that's what tells us the way the world really is the way the world really is doesn't include colors and sounds those things are produced in the mind of the perceiver and lead us to make erroneous judgments about the nature of external reality so that when we judge that a flower is yellow for instance we are making a mistake the flower is not yellow it's something which is produced in us at experience which is produced in us so real knowledge is achieved by intuition but yet we have real knowledge of the way the physical world actually is Descartes can rest easy now having established that science is on a firm footing and that we don't need to be skeptics as long as we believe that God exists and that God is not a deceiver then we can have peace of mind that the physical world is out there that the Martian robot is really the Martian Rover really is on Mars we can a peace of mind that the information it's sending us back is for the most part right now of course it's not entirely right because the colors aren't there for instance in Descartes picture and so you might say well gee isn't had a problem doesn't God sort of end up deceiving us in this case and Descartes says no that's not right actually is our fault because we have freewill and so we have the ability to endorse the information gained from the senses or reject it and so it's really our responsibility to be more careful and to think more carefully about the nature of our experience and then we won't be led into these traps will come to the conclusion on careful reasoning that the physical world contains shapes and objective mathematical properties but not the subjective things like colors and sounds and tastes so that people who are deceived in this way are deceived through their own fault by not paying close enough attention to the way things are presented in their experience so God is not to be blamed for this okay so now we've seen de cartes picture in general and now we're going to before we end this lecture look at a couple of well-known problems for the Cartesian worldview so the first one that we want to look at is based on the idea of the causal interaction between the mind and the body so it seems intuitively obvious that mental events cause physical events and vice versa so here are a couple examples my belief that there is beer in the refrigerator combined with my desire for beer can cause me to go up get the beer and have one so there we have cases where mental things beliefs and desires are producing physical activity getting up and going to the refrigerator again the itch on my leg can cause me to scratch it kicking me in the shin causes pain so there's a physical stimulation which causes something mental and a mental stimulation which causes something physical so again more commonplace is that my wandering something may lead me to ask the question which might lead me to make noises which cause me to hear the answer to the question so there seems to be just numerous common-sense examples of the relationship between the mind and the body and this is just part of our what's come to be known as folk psychology which is the views about psychology that normal people have so it's just part of our normal everyday ordinary conception of psyche of the way the mind works that there is constant interaction between the mind and the body okay we'll come back to talking about folk psychology when at the end of this class when we look at contemporary views about the nature of the mind and whether or not folk psychology it will be any help in this sense so the question for us here though is how did the mind and the body interact given that it's a common-sense view that they do now Descartes held that the mind and the brain communicated via what was known as the pineal gland so that his view really was that movements in the brain which are caused in a mechanical way by the mechanical bodies the material things out there result in an experience of pain or a belief or a desire or what-have-you and that this there was an organ in the brain where all of these things would be transmitted to the mind which causally produced the experience in the mind so the big question here is well how is this possible so the way that causation is understood at this period of time involves a physical connection between the two objects such as you would have in a billiard so a game of billiards there you have balls rolling around bumping into each other transmitting some of their kinetic energy which causes the other ball to move but you can't do that without some kind of physical contact between the things so that's what we mean by bumping here and the question which was recognized in dick carts own time asked by a famous princess in a letter to him to this princess had read his book very interested in it and sent him a letter saying my dear Descartes you know this is very interesting but how do these things ever causally interact and this was a big focus during Descartes time how can a non-physical mind bump into something which is physical and how could a physical thing bump into something which was not physical Descartes seemed to suggest that the way this works is that there's this kind of miss to this light wind somehow which alters the motions in the brain and of course the question came back to him yeah but that winds are physical right we can measure them we could quantify the force that's there so how do you get something non-physical bumping into something that is physical this is widely thought to be a very vexing problem for Day cards view now here's a more modern contemporary worry about Day cards view has to do with the discovery especially about 150 years after Descartes is writing so that'd be in the 1800s roughly when they started discovering various conservation laws for physics so physicists posit conservation of mass and energy what's basically you may have heard about this makes the claim that mass is not created or destroyed so for instance when we burn a piece of wood the amount of ash left over is slightly less than the amount of wood that you started with so if you have a 10-pound piece of wood and you burn it you will get less than 10 pounds of ash and this was very mysterious for a period of time when people thought that some of the wood was actually destroyed right because you have less of it at the outset then you get at the outset this was an empirical discovery of this time was that if you calculate the amount of energy released during the burning what you have plus the ash is identical to the original mass so instead of some of this matter being destroyed the view came to be that some of the matter was converted into energy in other words the heat that you feel when you're burning the log so that if you take matters you plus energy excuse me matter plus energy you have a conservation of the total net amount there's nothing added there's nothing subtracted everything since the history of the universe has simply been converting from matter to energy from energy to matter the two go back and forth and as I say this is any empirical discovery of this time there was someone who actually went and burned things of various sizes calculated how much heat was released and made sure that the actual material plus the amount of heat released were the same okay so if this is a discovery of science then it seems as though there's really a problem for dualism because how could it be the case that a non-physical thing could causally interact with a physical thing so this is not the problem of bumping which we noted early this is something different the idea here is that if the mind were somehow causing things in the physical world then you would find no conservation of energy you would find energy being put into the system so this is one of the very serious problems for dualism but notice that this is an empirical claim conservation of energy is a claim which is discovered empirically it could be falsified at some point not everybody thinks that this is right but most physicists at this point in history I think is safe to say have the have the view that the physical world is a causally closed system everything inside the physical world is causally sufficient to explain all of the effects on the physical world so there's nothing that happens in the physical world which merits the postulation of some additional thing outside of it the system seems all by itself in principle able to give a complete description of every effect which has ever happened completely in terms of material things and their interactions so for every bodily movement we can find some brain activity which is causally sufficient for that movement we've never had to appeal to any outside thing putting energy into the system so this seems like a very strong argument against dualism and of course we'll come back to this again when we get to the more contemporary period but again remember that at de cartes time the predominant argument against dualism would have been the idea about bumping and connecting the physical thing to the non-physical thing whereas the more modern and contemporary approach has been to wonder whether or not dualism is consistent with the laws of physics which we have since discovered so here let me just put this picture back up this leads to some very serious problems because now since you are the mental thing there you're making judgments the question is how do you know those judgments are accurate and so how do you know there really is a tree out there that corresponds to your image and of course that's in line with the question of how do you know that the Martian Rover is really on Mars and hasn't just been taken to some sound stage in Hollywood and you're not really driving around on Mars but in some other situation so there's that problem but notice also that since these experiences are private in the sense that only you know what they're like only you can tell what's going on in there nobody else has access to your experiences so you're sort of stuck in this mental area you're an expert you can't be wrong but no one else has access to it so this immediately leads to a problem about quality inversion so what I mean real quickly run through this problem because it's interesting so here's a fire hydrant which we would normally think of as red but remember that Descartes thinks the red is not out there on the object the red is something that's produced in the mind of the perceiver so here we have two perceivers there's Scarlett Johansson and there's Brad Pitt now let's suppose that Scarlett Johansson and Brad Pitt are engaging in some very very deep conversation so they're both standing around looking at the fire hydrant and they're both saying out loud that's red now of course it's totally open that what's really going on mentally is that when Scarlett is looking at the fire hydrant the fire hydrant is producing a conscious experience of what we would call red whereas what's going on with Brad is that Brad's looking at the fire hydrant and in him is produced the experience that we would think of as green so they differ in their conscious experiences even though they both agree that the object itself is called red now notice this would be very is very natural because of the way that we learn color words when you were young someone pointed at something and said look that's red do you know a color that is red and they were point out things like fire hydrants and ripe tomatoes and blood when it's been exposed to oxygen and etc and etc and etc you would buy a set of crayons and the crayons will be labeled and you variously come to associate certain words with the experiences that are produced in you buy these prototypical stimuli so you present the fire hydrant - baby Brad and baby scarlet and you point at it you say that thing is red and then scarlet has the experience on the left and she goes ah red and Brad has the experience on the right and he goes ah red so he's come to associate the term red with his experience which is what we would call green now Brad goes around calling red things red he and scarlet agree on every possible color discrimination you say go get all the red things they go go bring back all the same things you say here's a group of red and green things sort them into red and green and they agree on which ones are red of which ones are green there's no way that you could ever tell that this was happening this is a problem for Descartes because it seems intuitively very odd that there would be this kind of problem well I can't even tell if you mean by pain what I mean by pain if you mean by the taste of chocolate by what I mean by the taste of chocolate and notice that a lot of our normal conversations are based on the assumption that you do know what I mean because we'll say things like for instance you know that feeling that you get when you're on the roller coaster about to go over and that's what it was like and the person says yeah and I'm not feeling I love that feeling or I hate that feeling but of course now we have a problem how we even know that you're having that feeling at all or what's even worse is how do I know that you're having any feeling at all I not only may your experiences be radically different than mine on this view if it's right then your experience may not even be there there's no way that I could really tell if you were simply a zombie something that lacked no inner life whatsoever had no experiences at all one way to think about this is in terms of what happens in a video game so video games have gotten very good at having non player characters and these things are just little AI programs and they follow you around they give you ammo they make little snarky comments here and there but there's no real person behind any of those comments it's just a computer program so the question for Descartes is how do you know that this isn't really some complex version of that going on right now there's these other characters in your dream right and that's another case if you don't like the videogame game case when you're having a dream and there are people in your dream there's no real people there so if the person in your dream said I taste chocolate well they don't really taste chocolate they're just a figment of your imagination conjured up in a dream so maybe every person around you is like that and this is what's been known through time as the problem of other minds and the view that you're the only one that exists and that everyone else is a figment is a view known as Sol abscissa and these views are philosophical problems right we don't want to admit that we are the only person that exists we don't want to admit that other people are figments of our imaginations and don't have experience or have radically different experience than ours so then the question is how do we avoid that how do we how do we solve this problem this is one of the problems that Descartes left to us

Channel: Richard Brown

Views: 51,483

Keywords: Descartes René Descartes Mind, dualism

Id: fz0lU8kFQxs

Length: 52min 16sec (3136 seconds)

Published: Mon Oct 24 2011