4.3 Introduction to Cartesian Dualism

so let's move on now to another Cartesian topic dualism this is certainly the view for which Descartes is now best known if you find the word Cartesian in a philosophical text the most likely accompaniment is the word dualism Cartesian dualism is fairly straightforwardly stated he takes the body to be material made of matter whose essence is extension and he takes the mind to be made of a completely different substance immaterial substance non material whose essence is thinking so we've got two distinct substances now that's very important notice to be a cart easy and you listen uh you just think mind and body are different or even that mind and body have different properties you've got to think that they're different substances and that is a very substantial claim now in the discourse on method Descartes argue something like this I can doubt that my body exists I cannot doubt that I exist therefore I am not identical with my body quite a tempting argument at least to start with put yourself in the position of the skeptic what can I be sure of well the only thing I can be sure of is my own thoughts and my own perceptions so I'm absolutely certain that I exist but when I contemplate my body if it's all an illusion I cannot be sure that my body exists surely then my mind and my body must be distinct things for example I can imagine myself transported maybe to an afterlife or something like that in which I don't have a body but I still think I can imagine myself in that situation so surely I and my body must be dis things it seems quite plausible but actually as it stands this argument is fallacious so here's an example Hesperus and phosphorus are ancient names for Venus phosphorus is the Morningstar Hesperus the evening star the ancients didn't know that they were the same heavenly body they are in fact Venus of course is quite close to the Sun it's between us and the Sun so it only ever appears in the morning or the evening and never in the middle of the night ok so imagine somebody who does not know that Hesperus and phosphorus are the same and they might present this argument I can doubt that Hesperus is phosphorus indeed maybe I do doubt that Hesperus is phosphorus but I can't doubt that phosphorus is phosphorus therefore Hesperus isn't phosphorus because Hesperus and phosphorus have different properties ok one of them I can doubt to be phosphorus the other one I can't doubt to be phosphorus and there's no way that the same thing can have different properties so that's appealing to a rule called Leiden it's is law in fact Leibniz law is used in different ways by different people but this is one particular form of it if a and B are the same thing then any property of a must also be a property of B so if you have FA that means F is a property of a and a and B are the same FB follows so if F is the property of being doubted by me to exist a is me and B is my body we get Descartes argument from the discourse and by suitable substitution you can get the argument that I just put about Hesperus and phosphorus but you can see that this is fallacious if you put the problem if you count as a property something like being doubted by me to be to be Prime Minister you can get I don't doubt what the Prime Minister is the Prime Minister I doubt that Gordon Brown is the Prime Minister therefore Gordon Brown isn't the Prime Minister very easy to produce lots of examples of fallacies and the simplest way to avoid it is simply to highlight that being doubted by me to be something is not a genuine property of the object when I doubt whether Hesperus is phosphorus my doubt is not a fact about that planet it's a fact about me and it's about the fact that I am not aware that the appearance of this planet in the morning is an appearance of the same planet that appeared in the evening some weeks ago it's not a fact about the planet so much as about me so that argument of Descartes is well known to be fallacious but he produces a more interesting argument in the sixth meditation which is certainly much better but has questionable premises and it goes like this when I contemplate myself I can very clearly understand myself as being a thinking non extended thing I can see at any rate but I'm definitely a thinking thing because here I am thinking so I'm obviously a thinking thing and I can have a clear understanding of what thought is sufficient to enable me to see that I am potentially not an extended thing I also likewise have a clear understanding of body as extended and not thinking so when I contemplate a physical object I'm aware that it is necessarily extended and I'm also aware that it is not essential to its being but it be a thinking thing indeed it seems hard to see how a physical extended body can be a thinking thing certainly doesn't seem to be essential to it that it be so well if I can clearly understand what it would be for me to be a thinking thing and not extended and for extended things not to be thinking well in that case it's possible for God to create a world in which these things that I'm clearly understanding as possibilities are actual truths and it follows that if God could create me as a thinking thing distinct from my body as an extended thing then they must indeed be genuinely distinct things if they were not distinct God would not even God would not be able to create them as separate now I've mentioned that you've got a very crude argument in the discourse in the meditations you've got a much more sophisticated argument but even in the meditations Descartes does try to make this move from doubt to knowledge of his essence so here's a quotation what shall I now say that I am when I might be deceived by an evil demon or dreaming at present I'm not admitting anything except what is necessarily true I am then in a strict sense only a thing that thinks that is I'm a mind or intelligence or intellect or reason what kind of thing is that a thinking thing so notice what he's doing he's using his skepticism remember he started out saying I'm not going to accept anything except what is completely certain he then points out that he is certain of his own thinking and his own existence and moves on to say therefore I can be sure of that but that's the only thing I can be sure of I am a thinking thing but this is a dubious move distinguish two different meanings of a thinking thing what do we mean when we say that a thinking thing well we could just mean something that thinks or we could mean something whose essence is to think something which is in its own essence a thinking thing that cannot be anything else that cannot not think and those are two very different claims and the kind of move that Descartes is making here from epistemology to metaphysics that is he's arguing from how we come to know something to what it is that is in general a very suspicious move knowing that I'm thinking it does follow that I am a thinking thing in one sense if I'm actually thinking then I must be something whose which is capable of thinking at least if you don't put too much stress on the word thing but it doesn't at all follow that I'm something whose essence is to think so suppose for example I mentioned a couple of lectures ago about John Locke coming out with this speculation that God could make matter think so imagine God took a stone and made it think and the stone thinks to itself far I know I'm a thinking thing okay even the stone only knows that it's a thinking thing it doesn't know it's an extended thing because it has the same problems as we do it's only aware of its own perceptions it could then conclude that it was something whose essence is to think and it would immediately be proved wrong when God withdrew from it the power of thinking and the stone would still exist what about the final move of Descartes argument this seems rather more defensible though on the face of it it might seem dubious God could have created my mind and body as separate entities therefore it is possible for my mind and body to exist separately therefore my mind and body are in fact distinct things now at first sight this might seem to be committing exactly the same fallacy that I've just been talking about it might look as though something metaphysical a fact about what could be the actual distinctness of two things is being inferred from what is just a hypothetical possibility well it's very important that the possibility be understood in the right way so let me give you an example suppose I look up in the sky one day and I see Hesperus we could do later I look up and I see phosphorus maybe I don't know that anybody's even suggested that these are the same heavenly body or maybe the thought occurs to me and I say to myself well it is possible for Hesperus to be snuffed out while phosphorus survives maybe I'm thinking of some cosmic catastrophe that's heavenly body Hesperus could meet with some accident while phosphorus survives so there's a real possibility of one of them existing without the other therefore they cannot be the same object now actually there's nothing wrong with that last move but it depends on how you interpret possibility because actually when I speculate it is possible for one of them to be snuffed out while the other survives actually you can respond to that by saying no it isn't possible unbeknown to you it isn't possible because they are in fact the same object and if they are in fact the same object then it isn't possible for something to happen to Hesperus without it also happening to phosphorous but on the other hand you might be cutting glad to say well surely for the person in that situation contemplating these two objects it is a real possibility yes but only epistemologically when you say it is a real possibility there what one means is for all I know for all I know one of the objects could meet with a calamity while the other ones have eyes yes that's true but that's a truth about my knowledge it's not actually true that one of those objects could really meet with a calamity while the other does not because they are in fact the same object so again you have to be very careful when you talk about the properties of mind and body and so forth or indeed heavenly bodies are you actually talking about your knowledge of them or are you talking about their own properties essences etc Hesperus and phosphorus are in fact the same object at least that's what we believe because you might think well scientists could discover you know next week that there's been some some great hoax and they're not actually the same object after all yeah sure for all we know in a sense that could happen but if they are the same object in fact then whatever happens to one of them must happen to the other okay so when Descartes says I have a clear understanding of myself as something that thinks and need not be extended all that we should allow him is that for all he knows he is something that thinks and isn't extended from that it doesn't follow that he actually is something that thinks and isn't extended so Descartes arguments the dualism are not actually particularly strong ones if we draw this this clear distinction between epistemology and metaphysics we refuse to draw inferences from what from the fact that we simply have doubts or don't know things then it's hard to get to substance dualism there are also some major problems for Cartesian dualism one of them a famous problem how can two such distinct substances interact at all a problem that's very often thrown at Descartes if I consists of mind and body and the mind is purely mental it thinks but it's not extended and the body is purely extended and doesn't think how can the two ever come into contact with each other seems very hard to understand now this is a real problem for Descartes because Descartes thinks causation is ultimately intelligible he thinks we ought to be able to make sense of causation as for example when he says that any calls must have as much perfection or reality as its effect he's claiming to have an insight into how things cause other things but if we take david hume's view of causation then the position is very different remember David Hume came in the wake of people like Newton and Berkeley and Newton had said when it came to gravitation sure we can't understand we can't make intelligible why one object attracts another with a force inversely proportional to the square of the distance but when we look at the way things work in the world it turns out this is what happens and humeral eyes that and said quite generally even with billiard balls actually when you think about one billiard ball bashing into another it's very familiar so it has that feeling of naturalness about it because it's familiar but if you put yourself in the position of Adam the first man who's never seen billiard balls before he would be as mystified by that as we are mystified by gravity if you think causation just ultimately is a matter of one thing following another what we call law like connection then why shouldn't there be law like connections between mind and body so there's a bit of a sort of nice irony here that that Hume have all these philosopher philosophers of this period is probably most opposed to Descartes actually if you take a human view of causation what looks like a really serious problem for Descartes actually goes away doesn't actually go away completely there is a genuine issue here about how you would even try to formulate the sorts of laws that might hold between a mental substance and a physical substance even if you don't go with the problem of intelligibility even if you don't demand that the causal laws be intrinsically intelligible or natural trying to formulate any sorts of laws that you might have to connect physical phenomena with mental phenomena is quite a challenge another problem commonly thrown at dualism hinges on the causal closure principle on the causal closure of physics the idea of this is that only physical events can cause physical events so physics is causally closed in the sense that if you want to look for an explanation of any physical phenomenon you have to look at physical things now it's often said this is a major problem for cartesian dualism because if you're a duelist then it looks like you have to deny causal closure why well because mental events are causing physical events all the time I choose to raise my arm that's a mental choice and yet it has a physical effect but if the behavior of my arm is entirely determined by physical causes what room is there for a distinct mental cause how can it be some other substance and mental substance influencing the behavior of this physical substance but in fact I don't think the causal closed your principle isn't nearly as worrying for dualism as many think because the question is what basis do we have for believing it why should we believe that physics is closed in that way and we do these experiments in the laboratory all sorts of very clever experiments that measure things to fantastic precision sure there we might find that everything is explicable in physical terms but nobody's ever tried to do any sort of realistic experiment on what's actually going on in a human brain when we think if it were in fact the case that there was an immaterial substance there influencing how the atoms move how on earth would you know so it looks a bit like a prejudice the same kind of prejudice that you know when Einstein famously said God doesn't play dice in other words in Einstein's view everything in the world is physically determined he was just voicing a prejudice he didn't have a good reason for saying that of course the progress of science can lead us to think that everything will be explained in due course in terms of physical laws but the idea that we're anywhere near close to doing that is just fantasy so I don't actually think that objection is nearly as strong the causal closure principle seems really to to voice more an ambition or a name of science rather than anything that we've discovered but even if we do deny the principle certainly mind-body interaction seems peculiar more significantly I think it's hard to see how an immaterial mind could have evolved I think objections from the theory theory of evolution a far more worrisome for the dualist do animals have Minds at what point in the sequence of evolution do Minds appear well do you have to say that minds are not all or nothing if you're going to allow a mind to evolve as a separate substance does it mean you've got to have separate substance right there at the start Ameobi and so on microbes

Channel: University of Oxford

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Keywords: yt:stretch=16:9, philosophy, dualism, descartes, scepticism, mind, body, knowledge, truth, meditations

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Length: 22min 13sec (1333 seconds)

Published: Thu Oct 21 2010