6.4 Making Sense of Perception

okay let's move on to consider the issue of perception in a little more detail I've suggested that realism can be defended it can be defended as long as we're prepared to relax the requirement of intelligibility but that's not the only way in which realism can be attacked so Locke famously is an indirect realist when I perceive a tree there's an idea in my mind that's what's directly I directly perceive in the sense that I'm directly aware of the idea of the tree in my mind and I assumed that there is a material object which is the cause of this idea this naturally brings the so-called veil of perception problem how do we know that there really is a material object as it were beyond the veil of my ideas does this trap me within my ideas well it can seem to do so particularly if you're tempted by what I shall call the unacceptable interpretation now it is possible to parody in direct realism like this okay there's a tree out there I'm looking at the tree how do we explain it well we explain it by postulating an idea in my mind an idea of a tree which is in my mind okay so I see the tree by seeing the idea in my mind now what does seeing the idea in my mind amount to well maybe there's a little homunculus a little me in there looking at a screen and on the screen is an image of a tree and that's the idea of the tree so I see the tree by the homunculus in here seeing the image of the tree now that clearly is not explanatory because it's explaining perception of the tree in terms of perception of the idea of a tree and that's not got us anywhere it's replaced one mystery by another mystery so that interpretation I take it is clearly wrong and certainly that can that can naturally lead to the following sort of puzzle you know if you think about it what happens when you see a tree the image on your retina is upside down right because of the way the eye works as a camera and it could seem really puzzling that we don't see the tree as upside down why if you think about it shouldn't be so puzzling at all why should you expect it to appear upside down unless you are trapped by the unacceptable interpretation unless you're thinking that somehow that image has to be seen the projection of that image onto the retina just is part of the process of seeing and by some intricate mechanism that we vaguely understand but not very well hopefully in the next fifty hundred years we'll get to understand it a lot better we are aware of the tree through by means of this physical process but it is not because there is some little man in there looking at a screen now twentieth century philosophers have tended to prefer to talk about sense data rather than ideas but beware when you read stuff about sense data there's always this temptation to think of it in terms of the unacceptable interpretation it's much better to say that awareness of a sense datum counts as perception of an external object so it's not that you perceive a sense datum and thus perceive an external object rather you are aware of the sense datum think of the sense datum is simply the way in which the object appears to you but how can we know that there really is an object out there as it were beyond what we are immediately aware of how can we prove that causal link well here is David Hume presenting the problem in his characteristically pithy way it is a question of fact whether the perceptions of the senses be produced by external objects resembling them how shall this question be determined by experience surely Hume says experience is the only way but by which we can establish any causal connection but here experience is and must be entirely silent the mind has never anything present to it but the perceptions and cannot possibly reach any experience of their connection with objects thus opposition of such a connection is therefore without any foundation in reasoning so here's the challenge once you accept that there is a difference between the object out there and your perception of the object however you interpret that a sceptical question can be raised how do we know that there are any objects there and what Hume is saying is we only directly perceive or we're only directly aware of those perceptions of things as they appear how can we ever establish a reliable causal connection between the supposed objects out there in our perceptions if we're only ever acquainted with our own perceptions we never get the gods eye view to see this correlation between objects and perceptions so how can we know that there are any objects well one attempt that was made particularly in the 20th century to get around this though it you can see very much themes of this in Barkley's work is so-called phenomenalism phenomenalism is the view that physical objects are logical constructions out of sense data so statements about physical objects are to be interpreted in terms of statements about sense data so saying that an object is in a particular place is like making a statement about what you would perceive in certain circumstances so saying that there is a lectern here is making a statement about the perceptions that I or you would have if we made certain movements those perceptions would correspond with the parent experience of a lectern and maybe the physical existence of the lectern just is to be analyzed in terms of those perceptions well that's trying to get round the sort of Berkeley an argument Berkeley wants to say that you can't make sense of physical objects in abstraction from perceptions here is an account that actually aims to analyze physical object as perceptions it also is trying to get round the veil of perception problem if if I am acquainted with my own perceptions and if physical objects just are to be analyzed in terms of my perceptions then it looks as though we can get round that skeptical worried or at least it might look like that here again just as we saw we've seen before the problem of horizontal skepticism can be raised just as effectively phenomenalism is trying to get round a kind of vertical skepticism by saying well if we can't prove this exist the existence of this different kind of thing the physical objects let's just analyze those in terms of what we do know about namely our own perceptions but again we can raise the problem of induction suppose you do analyze the existence of a physical object in terms of perceptions that you would perceive in certain circumstances you've still got the problem of justifying the claim that those predictions are actually true well phenomenalism was very popular in the in the mid twentieth century it hasn't been so popular since much more popular since Jay Austin and PS strossen has been to insist that we perceive objects directly so the claim is that instead of being in direct realists in the way of Locke instead of saying that we perceive objects as it were by having ideas of them each we should say instead that we perceived them directly what does that mean what does it mean to say that we perceive objects directly well in one sense it seems definitely right insofar as it counters the unacceptable interpretation if somebody thinks that we see objects by means of a little man in the head seeing a screen that's dead wrong we do not perceive our ideas we perceive objects so when I look at a tree it's the tree that I see it's not an image of a tree however and this is the problem with it there is no question that my seeing the tree is mediated by a physical process which involves things like light rays and so on impacting on my retina involves signals going up the optic nerve involves the brain doing all sorts of clever jiggery-pokery which somehow makes me aware of the tree simply insisting that the only thing I see is the tree while in the sense that's true I do see the tree I don't see an idea of the tree in anything like the same sense that doesn't actually unfortunately help the skeptical problem because the skeptic can still perfectly well say look the experience that you're having I grant you if it is caused by the existence of a tree in the appropriate way then I grant that you're seeing the tree I'll even grant that you're seeing it directly if that's the language you want to use fine but how do you know that it is in fact caused by the existence of a tree how do you know you're not a brain-in-a-vat etc so the insistence on direct perception though it does have some point I think particularly encountering the unacceptable interpretation doesn't really help against the skeptic it merely gives a verbal solution as it were rather than a genuine one well can we move back to a sort of Lockean position a Lockean position which accepts that there is a difference between the object itself and how the object appears to us we have to draw that distinction we have to be aware that there are potential skeptical worries here that it is possible logically to distinguish the one from the other and therefore that it's not a logical impossibility for me to be in the situation as of seeing a tree without there actually being a tree there I could be hallucinating I could be a brain-in-a-vat and so on well to get rid of the unacceptable interpretation instead of thinking of an idea as a little image of a tree instead think of the idea as what we might call an intentional object so it's not like a little tree in the mind it's rather how a tree appears to me well that's a bit difficult to pin down it's not exactly an image it's not really an object at all nor is it really an explanatory thing within the the the causal story of how my perception comes around rather what we're saying is this when I perceive a tree there is a characteristic experience of what it is like to perceive a tree and since we can distinguish that experience from the actual being of a tree let us talk about the idea of a tree as capturing just that it's not an object but it's what it's like to see a tree okay is that still a representative theory of perception well who cares what we call it a lot of Locke's language can plausibly be understood in that way not in terms of ideas as little things projected on mental screens but rather in terms of the way in which we encounter objects to read more on this again we're getting here into some quite deep issues we're trying to cover them in the compass of a lecture is quite tricky I think John Mackey's book problems from Locke gives a pretty good discussion of this sort of approach pages 40 47 to 51 as I've indicated there well in that case what we end up doing is going back to a Lockean indirect realism in a sense it's indirect in a sense not all right we're not saying that there there are these little ideas that are somehow intermediaries we rather reflecting the fact that when we perceive objects there is an experience that it is like perceiving those objects and one can draw this conceptual distinction between our awareness of them and the existence of them so how do we justify the existence of those objects how do we get round Humes problem where he says you never experience the link between the objects and the perceptions so how can you justify the claim that there are any objects there well we justify the existence of the external objects in terms of their scientific explanatory nur's how things appear to us is explicable in terms of mechanisms that attribute causal powers to these objects that explain them in terms of physical intermediaries like light rays like sound waves and so on and these explanations do actually enable us to predict the things the way that things behave so as I mentioned earlier we can think of physical properties things like size and shape and so on as corresponding structurally to our ideas of them and we do find in fact that if we make predictions based on that the predictions tend to be reliable by attributing a ball or a block or whatever with a particular size and shape and physical properties corresponding broadly to our conception of them we can end up with predictions about what we will perceive that end up broadly right so isn't the simplest explanation there rather than going to Barclays God which is supposedly Orchestra the whole show to suppose that there really are things out there something like at least structurally something like our conceptions of them now these explanations the causal explanations of how things behave of how things bring about our perceptions those explanations are going to be have to be in terms of the object real qualities but we can drop the requirement as we've said that those real qualities that we attribute must resemble our ideas we are free to give explanations in terms of things like charge and spin and strangeness and whatever we should not feel trapped by the paradigm of the 17th and 18th centuries when so many people were looking for a scientific explanation that would inevitably appeal to real qualities that had ultimately to resemble our ideas we have to be prepared to accept that the world as it is out there is actually more radically different from our ideas than even the scientists of that time thought it to be thank you

Channel: University of Oxford

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Keywords: oxford university, lecture, student, Peter Millican, philosophy, perception, realism, idealism, phenomenalism, austin, strawson, locke, hume, berkeley

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Length: 16min 37sec (997 seconds)

Published: Thu Apr 14 2011