Hume 2: The Problem of Induction

okay so but changing from humans view about the opry re to his views about matters of fact we can say that matters of fact on the other hand have their truths determined in a different way so remember relations of ideas are made true by the relationship that hold between ideas matters of fact on the other hand are determined by the way the world happens to be so now fumes big target here is the concept of cause and effect as it's being used in the Newtonian sciences of the day and he wants to show that cause and effect is a matter of fact and the argument that he wants to develop rest on the two criterions - excuse me - criteria that we've already made use of in the earlier parts of this lecture so when something is a matter of fact you can deny it without contradiction and you also cannot know without experience what the thing will be so remember those all the things that were relations of ideas had these two elements to them if you denied them you got a contradiction and you can know that they were true without having to go and check the world so matters of fact are the ones that don't meet these two criteria they can be denied without a contradiction and you can't without the right kind of experience know what's going to happen so cause and effect certainly seem to fit that bill it does not seem as though you can tell what will cause what without going and looking and it certainly seems as though any time you imagine the opposite happening you don't get the contradiction so just to remind ourselves of what Hume actually says here he says look you know imagine that Adam was created one day and Adams got perfect rational faculties he never confuses denying the antecedent with modus tollens or anything like that right so he's totally rational in this sense and he pops into existence one day God says let there be life and here he pops up and now Adam is sitting here looking at a body of water like a lake Hume says look could Adam though his rational faculties be supposed to be perfect know that water will drown him if he walks into it and of course Adams never had any experience with the world so it certainly seems possible like you walk in the water you start breathing there doesn't seem to be anything contradictory in the idea of breathing underwater and you can't really tell unless you do it I mean the reason we know that you can't breathe underwater is because people have drowned so we've learned from experience that people can't drown excuse me keep people can't breathe underwater so these kind of causal relationships that going underwater will cause you to drown that kind of thing seem to be based in experience but if they're based in experience then we need to have an impression from which they're derived so he wants to know where is the impression of cause and effect so here's some little fancy computer animation here just to illustrate the point here comes a stick now of course we can ask did that stick cause the ball to move and of course the answer is no this is just a little bit of computer animation what happened was first you saw the stick on the left move and then you saw the stick the ball on the right moved to the right and you then conclude ah the first thing caused the second thing to move and that's pretty obviously wrong since this is a computer simulation but Hume thinks that roughly the same thing is true in an everyday ordinary observation of two things happening in a cause-and-effect relationship so suppose you have some ball and you hold it and you drop it and the ball begins to fall to the earth where there do you see the cause and effect Hume argues that what you actually see is first me holding the ball then you see the ball being released and then you see the ball moving through the air to the ground and nowhere in that sequence of events event 1 holding ball event to releasing ball of and three ball moving towards ground nowhere in there can you see the actual connection between them that makes it necessary that the ball move straight down so let's put this in a you know in a slightly more formal way so what's doing a lot of the work and is behind the scenes at this point is that Hume really is after a concept of cause and effect as the idea of a necessary connection between events and this really is the idea which you would get from someone like Newton someone in a physicist or something like that who thinks that for instance F equals MA it's necessarily true and describes the way that the world around us works such that that's impossible for there to be anything which could happen besides the ball of this mass moving at that speed if you applied this force to it right that this describes is something which is true everywhere and which must be true or to put it slightly differently to say that the connection is necessary is to say that the same effect will always follow from the same cause and Hume wants to say we don't get the idea of necessary connection between events from reason and we already know why because you can deny it without contradiction there's nothing contradictory about imagining that you drop the ball and it flies around your head instead of falling to the ground and you don't know what's going to happen to you actually do it so we don't get it from reason and Hume also thinks we don't get it from experience you never see the necessary connection remember you never see the thing this is the claim that he's making you never see the thing which makes it necessary that this effect was what happened as opposed to something else what you see is the first thing happen and then the second thing happened but nowhere in there see a connection between them what somehow indicates that the only possible thing which could have happened was the thing that you saw that's not something that you can get from looking at the series of cause and effect so you stick your hand in the fire you feel the pain you now think I every time I stick my hand in the fire I'll feel the pain and human is yeah but why do you think that what makes you so confident that the next time you stick your hand in the fire you will experience pain there's nothing in your experience which you can appeal to and say this is the thing which guarantees that the next time I'll feel the pain since the idea cannot be traced back to an impression Hume argues the idea of necessary connection is meaningless we have no rational reason to expect any cause and effect relation to hold in the future and Hume says make remarks like you know I drop a pen and I have no more rational reason to expect that it will fall to the ground and make a sound as I will that it will fall the ground and cause of the destruction of the entire universe no rational reason to prefer one over the other all of our inductive knowledge Hume thinks is founded on our belief that the future will resemble the past boom our belief that the future will resemble the past or that the way things have happens regularly over time is the way that things must happen and will continue to happen and Hume doesn't think that we're justified in believing this on rational grounds or to put it another way this belief is completely irrational we have no rational reason to believe it now of course we all believe it I believe that the laws of physics are going to remain pretty much the same over the course of the next hour by humans arguing that we have no reason based in our rational nature's which show us that this is right and so whatever reason we have for believing it it must be some other kind of reason okay so let's step back summarize the argument so far so all human knowledge is either learn from experience which is a matter of fact or it's something which we get from reason which are the relation of ideas matters of fact are composed of ideas which are copied from impressions and our true or false depending on the kind of experience we have so notice dogs can fly and dogs don't like cats are both matters of fact in that sense because whether they're true or not depends on the kind of experience we have there's nothing contradictory and a flying dog I haven't had an impression of any flying dog but it's certainly possible that there be flying dogs so the reason that I know that it's false actually that there are no flying dogs is because I've had lots of experience with dogs and my experience so far tells me that dogs can fly is false or in other words it tells me that dogs can't fly so it'd be a mistake to think that matters of fact means those things which are true when Hume simply is meaning the way you know that they're true is by experience so you should hear the phrase more along the lines of as a matter of fact dogs can fly is false but it doesn't have to be false and it has a matter of fact dogs don't really seem to like cats that much although there's nothing contradictory with a dog liking a cat and I've actually had some experience of dogs and cats getting along so I might think that that's false although generally true or something or something like that now relations of ideas are true or false depending on the relations that hold between the ideas so triangles are four-sided objects is something that I can know to be false because of the relationship that triangle has two three side so relations of AI are all those things which you can tell are true or false merely by inspecting the relationships which hold between your own concepts where as matters of fact are those things which you know to be true or false depending on the kinds of impressions you actually have the kind of experiences you actually get now again you can tell the difference between relations of ideas and matters of fact by seeing what happens when we negate the sentence in question so if you get a contradiction then you know you're dealing with a relation of ideas and if you don't get a contradiction then you know that it's a matter of fact so triangles are for started objects is a contradiction dogs can fly is not a cup of tradition now all of our ideas must be in one of these two categories their truth must be determined in one of these two ways and one of the more important ideas that we have is the idea of cause and effect which again is a code for the idea of a necessary connection between events which again is code for saying that the same cause is going to give rise to the same effect every time no matter what and this is very important because all of science is based on it this is why we do experiments because we think we can isolate the causes in many cases and we can tell that every time you do this you're going to get that and we depend on that in a lot of ways as for instance when you build a tire of a certain kind that you want to withstand a certain amount of turn force or something like that we depend on these kind of inductive observations that we make and even more than that our common-sense views about the world is based on this idea that you can learn the way the world is from observing it and that the thing the things that we observe to happen in the past are going to continue to happen that way in the future so that I'm not worried that tomorrow artichokes will be poisonous because I've been to plenty of artichokes they've they're harmless everyone knows they're fine so I don't expect that to change in any way and so too I expect the floor to remain stable underneath my feet as I walk around and there are many examples we could go on and on and on about okay but the problem is that we need to know where the idea comes from what makes it true that F equals MA or that every time I put my hand in the fire I will experience pain well as we've already looked and and said it can't be from a relation of ideas so fire causing pain is not a matter of a definitional thing like that fire by definition causes pain although it might be definitional that fire is hot it's not definitional that heat causes pain and you can see that because any of the causal relationships that you postulate can be denied without contradiction so I can stick my hand in the fire and feel pain but I can certainly imagine putting my hand in the fire and feeling no pain and you had nothing being different you can imagine putting my hand in the fire and instead of feeling pain I feel a tickling sensation or I taste chocolate or I get transported to the moon or you name any sorts of anything else could happen so there's no contradiction of course that's not the way the world has worked in the past and no one is denying that but the point here is that there's nothing contradictory in the same way as saying that some triangle has four sides which is truly a contradiction and it's always possible to imagine something else happening so I can always imagine that putting my hand in the fire produces some other kind of experience besides the feeling of pain so I just went through a couple of those and of course it's very different than saying yeah but I can imagine what a square circle would be right so some things are imaginable like that pain produces the sensation of tickling but some things are not imaginable like that squares can be round and of course the other end of this claim is that we have to go and check to see what follows from what so you can't tell what causes what without the right kind of experience that was the point of the atom water example and of course this is just something we know from common sense so think about mushrooms there are a lot of kinds of mushrooms most of which are poisonous some of which are edible how do we get the knowledge of which ones are edible well by people eating them and then dying in the one hand in case and now we say that mushroom is poisonous and passing that down and then people eating them and not dying we say how that mushroom is edible people eating them and hallucinating and we say that mushroom is hallucinogenic but it's not as though we can tell what caused a mushroom will have simply by looking at it we needed tons of experience in order to know what's going to proceed from what and of course again the common sense point is that's why we do science if we knew what follow for what by reasoning we wouldn't have to do actual experience experiments to figure out for instance whether or not bodies accelerate at a uniform rate or whether or not mushrooms are poisonous okay so all of our knowledge of cause and effect must be a matter of fact which is to say that it's got to be verified or falsified by the kind of experience that we have so the idea of necessary connection has got to be traceable back to an impression notice that Bachelor is not traceable back to an impression but it's still meaningful because it's connected by definition to ideas which are so if necessary connection might have been like that definitionally true but it's not so there's got to be some impression some actual experience that we have which vindicates it otherwise remember the idea is meaningless but Hume argues when we look at any example of a causing be all we see are separate events we see a happen we see B happen right after but we don't see anything that connects those two events the pool stick moves connects to the pool ball the ball goes flying off in some direction we see a chain of events one two three but we never see anything that binds or ties them together there is nothing you can point to and say look there it is that's the thing that makes the second occurrence a necessary consequence of the first occurrence or in other words every time you do it this way with that thing is going to happen in exactly the same way you never can find anything in your experience which allows you to do this and notice that even the laws of physics that Newton developed like f equals ma are not deduced a priori but a rather extracted from the empirical data so what Newton actually did was to look at very carefully and all the records that Galileo kept and to fiddle with stuff until the numbers came out right so that the laws of physics as stated by people like Newton are actually arrived at by careful observation and induction about the way the world works and then on the basis of that they make the claim that it's going to work this way always and forever and it's really that claim that Hume is taking issue with we're in our experience do we find the justification for saying that it's always going to happen that way now if we were rationalists we might say we don't get it from experience we get it from reason but Hume is concerned with arguing with empiricists he wants to show that empiricists can't help themselves to the idea of a necessary connection between events and so shouldn't be so confident about mathematical physics at least in the sense in which it says necessary and universal so Hume concludes we don't have any rational reason why we looked our relations of ideas is not there we looked at matters of fact we try to find the connection in our experience we can't find it so we have no reason to believe that the laws of physics are necessary and universal now this isn't to say of course that we don't know things have worked this way for a very long time but we don't have any reason to expect them to continue so humor really thinks that inductive knowledge is based on the fallacy of assuming that the future will resemble the past but remember the Black Swan just because something has happened for a long time is no guarantee that it will continue to happen it doesn't matter how many times you've seen the Sun Rise every day so far you can't say with certainty that it will rise tomorrow even though for millions of years the Sun is risen does the largest sample size of anything known to man it doesn't mean that it has to rise that it's necessary that it rise so to just because you've seen things fall to the ground for all your life gives you no rational reason to expect that they'll continue to fall to the ground and behave in the same uniform way that they have behaved and as I said this is exactly like the problem of black swans we talked about in the logic section when we talked about inductive logic you can see a million of these things and it doesn't mean that that's the way nature must be so then why do we all feel so strongly that there is a necessary connection between events well Hume says what's going on here is that we actually have a habit of expectation you see a happen you see B happen right after you see a happen you see B happen right after repeat that you drop the thing it falls you drop the thing it falls you drop the thing it falls eventually you see a happen and your mind immediately comes to expect B ah he dropped it is going to fall and it's that habit of expectation that we mistakenly project out on to the events we observe so Hume thinks that this is another instance of what he calls spreading the mind onto the world around us we have this feeling that when you drop something it's going to fall because we've seen it that way a bunch of times and we mistakenly think that that feeling is indicative of the real connection between the events a and B but we cannot know if there is anything more to the world than this constant conjunction of one event following another so notice that this is an epistemological claim that Hume is making we can't know if there is a necessary connection between events he's not making the metaphysical claim that there is no necessary connection between events this is why some people think of Hume as a skeptic because of what he's arguing is there's just no way for us to really tell whether or not there is this necessary connection between events or not because it may be for all we know that things have been regular for all this time and then tomorrow you drop a ball in a float and nothing has changed if that's what we experienced tomorrow we would simply have to say well wow it used to fall now it's different just like when you see the first Black Swan doesn't matter how many times you've seen swans Wood for white in the past you meet a Black Swan and that's the end of the story there's the Black Swan so - if you drop a ball someday and it floats and nothing else has changed well then you'd must simply come to the conclusion that things fell for a very long time and they accelerated in 9.8 meters per second per second and that was fantastic but now things are different okay so what's very similar here - in what's in psychology known as classical condition and Pavlovian classical condition in particular now a few guys before Pavlov comes along and does his experiments but it's not very long after Hume that Pavlov is doing and Hume would have approved very greatly of this kind of work so what Hume thinks really is that we've been trained by nature to expect certain events upon seeing certain other events just like Pavlov's dog so just refresh ourselves about what Pavlov did so first you get some dogs and you drill a hole in their throat and put a tube in there that goes to a bucket and you start collecting their saliva so when their mouth waters it goes instead of another stomach into this tube and what you do is you keep these dogs hungry and so you ring a bell for instance around the dog you get no increase in saliva activity but if you bring around a piece of meat saliva starts accumulating you can measure how much saliva the the the meat produces so a Pavlov did is take these two things that are totally unconnected in nature the medes and the sound of a bell and he pairs them together so what he did is he rings the bell first and then he brings the meat the dog salivates because the meat there you repeat that ring the bell bring the meat ring the bell bring the meat ring the bell bring the meat before you know it the dog is salivating when it hears the bell ring whether or not the food comes so early on you ring the bell nothing happens you bring the meat saliva you ring the bell nothing happens you bring the meat saliva dot dot dot you ring the bell saliva from the dog even if you don't bring the meat so the dog has been conditioned to expect that the meat will arrive when it hears the sound of the Bell he's come to expect that this is true Belvin food but now of course imagine that the dog were to reason itself so to reason to itself so suppose a dog becomes a philosopher we might call him phyto so suppose phyto is thinking well you know every time the Bell has rang food shows up and in fact this happened my whole life every day ever since I was a puppy but all food Bell food this is clearly something which is necessary every time the bell rings the food will appear well of course we could easily see that the dog has made a mistake there's no connection between food and bell it's accident and we can even imagine that phyto works out a bit of mathematics and say you know develops an equation which describes the relationship between the intensity of the bell sound and the quickness of the food arriving so we can say suppose the bells very loud the food arrives shortly after the bells sort of dim the food arrives later and there's a nice inverse proportionality to excuse me a nice direct proportionality to the sound of the Bell and the quickness of the food arriving and so phyto might work out this nice little equation which describes this and it's true it described the way things have happened for a very long time just like our laws of physics have described the way things have happened up till now very reliable very regular but of course one day the bell will ring and the food won't come and phyto cannot protest oh but my equation said that it would if that relationship no longer holds it no longer holds that's because there's no necessary connection between the bell ringing and the food appearing in nature so Humes point how do we know this is not the way nature is for us maybe it's just this reliable conjunction of events maybe it's just been set up that way maybe it just accidentally is that way for this period of time which to us seems like a long period of time but there's no guarantee that it will always be that way none it's it's important to note that Hume is not denying that nature is regular he's not denying that up till now things have worked this way in exactly the way the physicists have described F equals MA is a perfectly good description of the way things have have worked for thousands of years but of course the bell ringing food bringing relationship seemed regular as well but if there really is no necessary connection between those events and there's nothing which would prohibit that relationship from changing no matter how many times you've applied this amount of force to a ball with that mass and God the Fung a certain acceleration no matter how many times that has happened if there's no necessary connection there's just no necessary connection so things have happened regularly and predictably but we have no reason to believe that it must happen that way from the mere fact that they have happened that we've experienced them being regular is equally compatible with the Pavlov kind of example as it is with there really being a necessary connection between events now switching gears a little bit in sort of wrapping up this section on Hume Hume applies this exact same criterion to the issue of the self so remember the self was supposed to be this permanent thing which exists through time for Descartes the self is the thing you know most directly and immediately that you exist as a thinking thing yourself which stays the same over the course of time you're the same you as was born oh those many years ago well of course if Humes being an empiricist if this idea is to be meaningful there's got to be an impression of it there's got to be somewhere in our experience where we find ourselves Hume argues that when he looks inside as he says when I quote enter most intimately into what I call myself and quote he never finds this thing that people are talking about what he finds instead are momentary impressions that flow by in an endless procession so you can try this yourself think about what you're experiencing right now the sound of my voice the feeling of a chair on your backside the background sounds a taste you have in your mouth maybe a smell it's hot it's cold you you're thinking about this you're wondering what Hume was thinking about etc but nowhere do you find this thing called the self it's not the body you see in the mirror since that's changed from the time you were a kid it's not this or that belief since when or this or that experience since if I'm looking this way and see a pumpkin for instance it's near Thanksgiving and Halloween while I'm recording this so I look over here and see a pumpkin but I look over here there's no longer this little orange oh orb in my sensory experience so that stuff is all changed and there's nowhere in there that Hume says you can find the notion of the self but now look at where we landed here Hume doesn't think that we can know that cause and effect is necessary we don't have any real reason to believe that the causal relationships as described by science will continue to work that way we can't find the self anywhere we look for the self but we find our momentary impressions nothing which unifies them they just seem now cold now hot now sweet now warm now wet etc and it's just going by now orange now blue now circle over there sound over here sound so how then can we go about our lives well Hume famously makes the distinction between himself as a person as an animal out there in the wild so to speak and himself as a philosopher sitting in his room thinking about this stuff so of course when he's walking down the street he sees a carriage coming his way and jumps out of the way of the carriage he doesn't stick his hand into the fire he doesn't stab his tongue with a knife or eat razor blades and for the same reason you don't because he expects that these things will cause them harm but this is just instinct this is just animal expectation just like the dog hears the bell and starts salivating it can't help it it's not a rational process it's just us in our instincts cranking away and Hume says I'm also a human being I'm also a person and I have these instincts but when I go into my study when I go to the my room and I start thinking about these issues I start to see that they're instinctual that they're conditioned that they're irrational and so it's perfectly consistent with for for him to act like he wants to protect his self from harm and to say things like I think and I believe even though on rational reflection he doesn't find that there is any real reason to believe in these things

Channel: Richard Brown

Views: 29,109

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Keywords: David Hume, induction, Inductive Reasoning, cause and effect, science Mind Effects Brain

Id: QiYGSR8xOec

Length: 33min 51sec (2031 seconds)

Published: Mon Nov 14 2011