3.3 The Problem of Induction

so without further ado let's go straight on to induction you'll see that here there are a lot of things in common with the material we've just covered so some of that I shall go over quite quickly however the handout aims to be relatively self-contained so that you can look at it separately the the people shown here we've got David Hume on the left so Peter Strawson who was at maudlin for many years and I think started out at University College so he's very much an an Oxford man Hume Ella until recently professor at Cambridge and Nelson Goodman famous author of the Goodman paradox now the main historical reading that you will get on induction is David Humes inquiry concerning human understanding section four and the discussion there starts with a vital distinction a very very important distinction and one that has remained of tremendous importance though its exact formulation has changed over the years Hume draws a distinction between relations of ideas and matters of fact well what's a relation of ideas well think for example of this proposition here all bachelors are unmarried okay so we've got certain ideas like the idea of a bachelor the idea of being unmarried and we can see just by looking at the nature of those ideas what we understand by them what do we understand by a bachelor well an unmarried man if that is our idea of a bachelor then we can see just by consulting our own ideas that all bachelors must be married three times five equals half of 30 that's one of Humes examples simply by examining our ideas of three and five and multiplication etc we can again see that that is true more complicated example Pythagoras's theorem it seems that the proof of Pythagoras theorem comes pretty much from just consulting the ideas of a Euclidian triangle the axioms of Euclidean geometry and simply doing inferences from those so these kinds of propositions are for human relations of ideas the more modern term is analytic propositions ones that can be known if you like purely by analyzing the meaning of the terms and Hume draws a distinction between relations of ideas and matters of fact now matters of fact are things that we cannot know to be true or false simply by consulting our ideas so he gives examples like the Sun will rise tomorrow the Sun will not rise tomorrow those are things that we cannot know to be true also be false just by thinking about our ideas of what the Sun is if we take a pen hold it in the air and let go of it before it's fallen the proposition that it will fall when released is a matter of fact it doesn't follow from the idea of a pen from what we understand by a pen from what we understand by releasing it in air it's not a matter of logic that the pen must fall it's a matter of fact so the modern term for that is a synthetic proposition a proposition whose truth is determined by the facts of experience rather than what we mean so this raises a natural question some matters of fact we can know to be true or we think we can know to be true just by perceiving them I can perceive that the selectin directly in front of me so let's not worry about that I can remember that it rained last week and not gonna worry about that what about matters of fact that I don't directly perceive and that I don't remember how can I possibly know anything about those and now we come to that example that's been mentioned before of the billiard balls paradigm example of a matter of fact I see it a yellow billiard ball moving towards a red one I suppose that when they touch the red one will move but that it will move is not a relation of ideas it cannot be known to be true just by consulting my ideas of billiard balls and movement it's a matter of fact and I can't see now that it's going to move and I clearly can't remember its movement because we're talking about something in the future so it's just an example of the kind of matter of fact that Hume is talking about so why do I suppose that the red one will move when the yellow one hits it according to Hume the only way we can ever draw any inference to a matter of fact which we don't either see or remember is by relying on causal relations so then we get to this famous thought experiment there's Adam as painted by Michelangelo Adams just been created by God he sees one billiard ball moving towards another put yourself in his position you have no experience at all to call on you've never seen anything like this you are asked to predict what will happen when the first ball meets the second one how could you possibly proceed according to humans we've seen you couldn't you would have no idea what was going to happen maybe when that ball hits that one it will just stop maybe it will explode maybe it'll go right through it maybe it'll turn into a frog who knows without experience you have no basis for any prediction so that means that any inference - a matter of fact beyond what we perceive or remember seems if you write to be based on assumptions of causality and all our knowledge of causal relations such as with the billiard balls comes from experience without experience we can't make any predictions about what will cause what and it seems clear that learning from experience takes for granted that observed phenomena things that we've seen in the past do provide a guide a guide of at least some reliability to what's going to happen in the future so it seems that in order to make any prediction about the future we have to take for granted or we have to have some basis for extrapolation extrapolation from our experience to the future because experience is our only guide well here's a passage from a letter from a gentleman to his friend in Edinburgh that Hume wrote in 1745 the context of this was that Hume was applying for a chair in moral philosophy at Edinburgh and the the clergy at Edinburgh were very much against him because they thought his treatise of human nature was atheistic and so he wrote a letter trying to explain how the treatise wasn't nearly as bad as people thought it was it's not exactly clear how much of this letter we should take as entirely ingenuous some of it might possibly be suspected of somewhat glossing over the truth but at any rate in that letter he explained part of the background to his epistemological thinking it is common for philosophers to distinguish the kinds of evidence into intuitive demonstrative sensible and moral when Jim talks about intuitive evidence that is intuition like Lockheed means something that is immediately self-evident so for example that something is identical with itself I am identical with me 2 is greater than 1 these are things I can know to be true just self-evidently by sensible evidence Hume means sensori evidence the end evidence of the senses demonstrative evidence well that's demonstration logical argument and by moral evidence Hume means inductive reasoning reasoning from experience it's very important when you read the inquiry notice that when human uses the word moral he does not mean ethical in the sense that your I would mean by moral so moral reasoning is reasoning about the world so here Hume is drawing on Locke we've seen before how Locke draws this distinction between demonstrative and probable reasoning and we saw that for Locke both types of reasoning involve a rational perception of the links so Locke's view of demonstrative and probable reasoning or demonstrative and moral reasoning is that in one case when we reason from one step to another in our chain of reasoning we see a clear evident connection from one step to the next in probable or moral reasoning when we reason from past experience according to Locke we see evidential connections but there are only probable connections not demonstrative ones ok with that background let's go back to Humes question we want to know why the second billiard ball will move when the first touch is it we think that the only ground of such an inference is causation we think that the only way we can learn about causation is from past experience and we want to know what ground we have for extrapolating from past experience to the future for expecting that the causal laws if you like that applied in the past will apply in the future what ground have we got well is it self-evident no it isn't can it be demonstrated can you produce a logical proof that what's happened in the past will happen in the future no you can't because we can perfectly coherent be conceived of it not happening do we have sensory knowledge can we see through our senses that what has happened in the past will happen in the future clearly not what about factual inference what about ordinary day-to-day inductive moral reasoning no because that is the very kind of reasoning that we're considering we're asking ourselves whether it is possible to extrapolate from past to future legitimately so relying on that kind of reasoning to justify our relying on that kind of reasoning would be going in a circle so here I give a very brief review of the argument of the inquiry I'm not going to go through this now in detail but when you come to Humes texts take a look at these slides and use them to inform your reading of these passages that's a summary of the part 1 argument where humor says that all factual inference is founded on experience it follows that all factual inference has to be based on an assumption of uniformity the assumption that what has happened in the past is a guide to what will happen in the future and then we get the proof that we have no ground for making that assumption so it seems as we've said before that all of our reasoning about the world all of the reasoning by which we reach any matter of fact at all beyond those we immediately perceive or remember is based on an assumption of uniformity a an assumption that what we have experienced is a reliable guide to what we haven't experienced and if you MS right that assumption is based on nothing at all other than animal instinct there is no rational basis for it whatever and that's the famous human skepticism about induction it's been an inspiration to huge numbers of philosophers of science it was seen by many as a complete crisis by some as an opportunity the kind of philosophy of science that you find it in in popper to some extent in kuhn and many many other philosophers of science takes it start from Humes results popper for example tried to give an account of science which in no way depended on induction because he thought that Hume had completely undermined that basis as I've said it seems to imply that our human reason that we tend to be so proud of is actually different from animal reasoning only in degree it's not fundamentally different in kind the sort of supposed perception of probable connections that Locke had thought was the basis of human reasoning turns out to be wishful thinking there is no such perception when we when we think that we have insight into the way physical things behave at bottom there is this assumption of uniformity which is based on no insight whatever and our understanding of causation is not really based on intelligibility it's based on observation of uniformity now I'm not going to say very much about Humes particular view of this but just very briefly does it imply a complete irrationalist point of view if you go with Hume on this does it follow that anything goes that there is no different between the scientist and the superstitious enthusiasts who bases predictions about the future on the shape of the tea leaves in his teeth in his tea cup or on tarot cards or astrology or any other superstition you care to mention well Hume didn't think so he did deny this inductive inference is founded on rational insight but he didn't want to say that therefore anything goes but that raises a major problem of demarcation and again this is a problem that has echoed down the centuries since what right do we have for preferring scientific reasoning to superstitious reasoning if the ultimate ground of scientific reasoning is just an animal instinct so we have animal instincts to be scared of certain things or to have certain superstitions why should we give any less respect to those than we give to our animal instinct that underlies science well Hughes answer is basically to favor consistency Hume wants to say that everything we do in life is based on the assumption that we can learn from experience and that the future will conform to the past we can't even wake up in the morning wash go out the door eat our breakfast without making assumptions that the behavior of things in the past is a guide to their behavior in the future even the entirely superstitious person has to rely in almost everything that they do on that assumption of uniformity and systematic behavior so Humes answer is to say well in that case the rational thing to do is to accept that accept that we are part of nature except that this assumption is one that we simply cannot live without and now follow through the consequences and if you follow through the consequences if you remain faithful to that assumption that the basic laws by which nature works are consistent over time since you have to assume it in your daily life why not make that the model and then try and systematize what you discover about the world in conformity with that that is where science comes from and according to Hume it gives a reliable basis for preferring science to superstition but it does mean that our attempts to understand the world are reduced to the kind of thing that Newton did in the case of gravitation the utmost effort of human reason is to reduce the principles productive of natural phenomena to a greater simplicity and to resolve the many particular effects into a few general causes but as to the causes of these general causes we in vain attempt their discovery so we have to make do with the science in which the ultimate principles are ones that we just have to accept and as I suggested in the case of quantum mechanics that is in fact where we are if you now look at what Hume has to say about science a lot of it will look like common sense at the time it was very far from common sense and it's a mark of how far we've come that we now accept that the ultimate principles of science are ones that we cannot hope to base on pure reason ok the last few slides I'm just going to go summarize very quickly many people have attempted to answer Hume in all sorts of different ways all I'm trying to give here is a little road map so that you can see where some of these attempts fit in to discuss them with any sort of depth would require at least another lecture or two so I shall not attempt to do that one way of trying to answer Hume is to show that actually induction can be justified by pure reason but by appeal to probability rather than demonstration here are some of the famous names of those who've tried to do this including Simon Blackburn and John Mackay both Oxford philosophers in their time Roy Herod other attempts to heat to answer Hume include the so called analytic justification of induction this is associated particularly with Peter Strawson the claim is that induction is rational by definition when we think of what is a rational way to behave basing your assumptions about the future on the past just is rational to assume that what's happened in the past is a reliable guide to the future that is what just what the rational person does how can we make sense of rational behavior which didn't do that and so the claim is that induction no skeptical problem can be raised about induction in the way that Hume was thought to do some philosophers have argued that induction can be justified by its past success inductive reasoning has always worked very well for us it's worked in the past should work in the future shouldn't it and the pragmatic justification of induction attempts have been made to show that even if we cannot justify relying on induction by pure reason we have pragmatic reason for doing so practical reason briefly I don't think any of these answers really hit Hume very strongly he would agree that we describe induction as a rational rational way of behaving he himself advocates that we rely on it an inductive justification does just seem circular it seems pretty obviously circular I think ultimately it pretty clearly is circular the pragmatic justification doesn't touch humans position because humor himself after all says that we irresistibly inevitably assumed that the future will resemble the past anyone who comes along to me with a pragmatic justification of induction who tries to preach to me and tell me why I should rely on it is wasting his time I'm already bound to rely on it it's the way I am the only question is whether I will rely on it consistently and finally I end with a couple of slides on hue Mela and on Nelson Goodman I'm not going to attempt to bring those into the discussion here I've put them there because they are amongst the reading that you will get on this topic and I hope that what I've written there will help you to assimilate that those into the general framework that I've given you next time we carry on with more topics on general philosophy see you then [Applause]

Channel: University of Oxford

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Keywords: yt:stretch=16:9, philosophy, Hume, induction, knowledge, truth, experience, reason

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Length: 22min 59sec (1379 seconds)

Published: Thu Oct 21 2010