Ep. 353: Reid on Visual Knowledge (Part One)

0:08 Mark: You are listening to the Partially Examined Life, a podcast by some guys who at one point set on doing philosophy for a living, but then thought better of it. Our question for episode 353 is something like, how does knowledge relate to vision? We read chapter six of Seeing from Thomas Reid's Inquiry into the Human Mind on the Principles of common sense from 1764, continuing our discussion of that book from our prior episode. For more information about the text and the podcast, please see partiallyexaminelife.com this is Mark Linsenmayer with eyes distorted in unnatural directions.

0:39 Seth: From Madison, Wisconsin, this is Seth Paskin, untutored by modern philosophy in Austin, Texas.

0:47 Wes: This is Wes Alwan Deferring to the Common sense of mankind in Cambridge,

0:51 Dylan: Massachusetts, this is Dylan Casey, Uncovering Laws of Nature as an Explanation of Cause and Effect in Madison, Wisconsin.

0:59 Mark: And so we continue this. On Seeing chapter is more than halfway the book. And we didn't read the whole thing. Maybe you did, Wes, did you read the whole thing?

1:07 Wes: Almost. The squinting. Two chapters skimmed over the squinting. I squinted at the squinting. I thought it was hilarious that there

1:16 Mark: was three chapters, I think, on double vision.

1:19 Wes: Yeah. So much information on squinting. Yeah. So he has some very technical chapters involving vision and the inversion of the image on the retina and various optical illusions and what that means. So I, you know, in our final assignment for this, we did some of that, but we also skipped quite a bit of it.

1:39 Seth: Right.

1:40 Mark: We had skipped the chapter on touch, though he refers to it a bit mostly in the contrast between the idea of shape that we get from seeing something and the idea of shape that we get from touching something and how, for instance, Berkeley said those were totally different things. Right. One of the things that Reid is picking up on, as we discussed last time, is that in general, the sensation that we get from something does not actually resemble that thing. That. For Berkeley, that meant that the picture in my head of a. If I'm looking at a horse or if I'm touching a horse, I'm smelling a horse.

Well, certainly that smell, as we said last time, in my mind, it ceases to exist when I'm not smelling that. That smell sensation. But that smell sensation we perceive as being connected, being causally connected to some objective thing in the world, a stink, an odor that would be there if you came along and smelled that. But it seems like the physical thing, whatever it is, this unknown quality that's giving rise to the stink, and this idea could not possibly have a resemblance relation, but in sight, there actually does seem like a resemblance.

Relation. And this is why we end up talking about the image that is on the retina is that, you know, are we somehow getting an image or something that corresponds, that resembles something out in the world? In some ways, yes. In some ways, no. We'll get into that. So that seems like a big, big point for that whole section.

3:06 Wes: Yeah, it's important that. Right? So in a way, he's fighting the copy. He's fighting, you know, it's kind of similar to people like Rorty. He doesn't like a certain brand of representationalism, and he doesn't like the copy theory of representation, which we know right off doesn't work for most of the senses, like smelling. We don't think that smells are copies of something out there, but we get confused when it comes to sight. And he's going to end up telling us that actually sight is more like smelling than you thought. That what you see immediately, what we see immediately in our visual field, which we seldom actually pay attention to, they're really more like language, like signifiers, like words on a page that we use to see straight through to the signified perceived thing.

That if we do pay attention to those signifiers, we'll find that they are actually quite dissimilar to the objects that they signify. And one example, right, is just we know, perspective. There are a lot of simple examples of which we are all aware that our visual field, you know, where, especially where if we've ever tried to draw or paint anything, if we want to represent parallel lines going off into the distance, say with train tracks, we have to make them on the canvas or they will inevitably, in our visual field, look like they are converging.

Look like they are just converging at some infinity horizon point. So they actually look triangular within the field. So we translate, you know, the language the. The signifier is, hey, look at this kind of triangular setup of converging lines. And we read that, and it depends on context, of course, but we read that as signifying. Hey, here are two parallel lines, not a triangle.

5:02 Dylan: And this is exactly the same explanation you'd have for all kinds of other judgments and interpolations of regarding how the signifiers are related to the signified. Using that language that you would read about, especially among early moderns, is trying to resolve some kind of error. You know, the bent stick in the water, or the jaundiced eye looking out in the world and having it be yellow and all other kinds of things like that. You know, the change of the hue of color because of the changing light. All of those are not examples of error. Those are just examples of different ways in which our seeing is.

Is working. It doesn't mean that there isn't a thing behind it that has properties that are its own properties independent of our seeing of it. Just like the parallel lines converging in the distance. Doesn't mean that there isn't a property of the lines of the road being parallel to one another.

6:05 Seth: Yeah, he does a really, really good job at the beginning of the seeing chapter to point out that. So you have the idea that the sensation is not a representation of the thing from smelling and touch.

6:23 Wes: It's not a resemblance, let's say.

6:26 Seth: Sorry, it's not a resemblance.

6:28 Wes: We might try to defend a broader conception of representation, but yeah, okay, I won't.

6:32 Seth: But okay, I'll say resemblance. So, you know, he starts talking about what happens when you look at an object. And we've referenced this many, many times before, right? That when you look at something, you see it in three dimensions. You know that there's a backside to it. You know that we've used this example a million times. And he, you know, points out that mechanically the representation of that external three dimensional world takes place on a two dimensional canvas that is, you know, he goes into the retina and so forth. But what hit home for me was when he said, nobody pays attention to the fact that the sensation that we have which comes across this color and gradient and yet, you know, yada yada, and is, is actually a two dimensional representation, signifies a three dimensional object.

Like nobody pays attention to that two dimensional sensation that generates the idea of a three dimensional object except artists and sculptors. And he says, a painter can't see the world the way human beings see it. The painter has to see the world the way it's sensed as opposed to the way it's idealized or ideated. And it brought me in mind of there's a really great documentary about, I think it's Vermeer. It's called like Tim's Vermeer or something like this, where in order to try to understand Vermeer's use of light and how he used this camera obscura to paint this particular picture.

This guy builds a replica of the painting and of Vermeer's studio in a warehouse in San Antonio. He shows basically how Vermeer might have done this. And essentially you cannot look at the picture. You can't look at the studio and the setting and paint it by the naked eye. You just can't. Because there are places where the light appears to be different, but in fact it's the same shade. It just has to do with the trick of the human eye, that when you see the same color next to one thing and next to another thing or in a different background or whatever, it's the same exact color, but your eye sees it differently.

So he showed how Vermeer might have overcome that. And I, like, the top of my head blew off. I was like, oh, my God, he's absolutely right. Like, we're doing all this work in our head, which we've kind of known. I mean, we know that our brain does all this work, but to then talk about, you can marvel at the fact that our brain creates that thing out of the sensation that it gets. Or in his case, he's like, imagine that the sensation is not that image that you have. And I just. I mean, I fell out of my chair. It was just mind blowing to me. And it has so many implications.

But that's the way in which sight is similar to smell, because the sensation that you get is not going to give you what it is that you actually idealize in your head.

9:45 Mark: Right. So last time I was saying maybe we are reconstructing objects out of these individual appearances. He wants to say he doesn't use words like that. It's just the famous in the Smell chapter that on seeing an appearance or smelling a smell, our mind immediately goes to the supposed cause. So, you know, I was also asking last time, well, does that mean we indirectly get at the object and directly only get at the thing in our head? He doesn't want to use any language like that. It's just that we gain knowledge, both of these immediate things, which, you know, we really don't actually retain much knowledge of that because our, for the most part, our mind goes straight to the thing that's represented. It doesn't dwell on the signifier, on the appearance.

10:30 Dylan: Unless you're an artist.

10:31 Mark: Yeah. And then we have knowledge of things out in the world. We just have the knowledge. And so after these 12 sections where he gets increasingly precise about optics, we skip down a bit to section 20, which was kind of rehash, for the most part, about realism and why skepticism is wrong. And I was sort of thinking this week's reading did not blow me out of my chair. I was not as impressed as you were, Seth. In fact, I was sort of thinking like, well, I kind of wish. I wish I'd known this last time. I would have been more precise in a few things. But this sort of Seems more like an hour long part three than a full episode. But then the last section before the conclusion that we read last time 24 of the analogy between perception and the credit we give to human testimony. That I was like, yes, this is. We could spend a whole hour and Wes will want to talking just about this.

11:26 Seth: You didn't think the fact that he says sensation works has the same mechanism as language, the whole idea of signs and signification, that they work in the same way was. That didn't rock you?

11:38 Wes: Yeah, that's what I'm saying.

11:39 Mark: I'm saying this part rocked me. Not the earlier part.

11:41 Seth: You're talking about the second paragraph of the last section.

11:44 Wes: Yeah, I find it so. I mean I do. I just find the technical aspects of it pretty mind blowing. Including. Right. Something I hadn't thought much about, which is his claim that there's a non Euclidean geometry to the visual field. So it's not even just that it's two dimensional, it's two dimensional with a non Euclidean geometry and it has to signify a three dimensional Euclidean space.

12:07 Seth: Now can you explain?

12:09 Wes: Well, so for instance, in the visual, it's as if you're looking at. It's flat from our. Right. Okay, so it's two dimensional, but it's as if. It's as if it's a two dimensional field that has been projected onto the inside of a sphere. Right. So imagine taking a picture of Euclidean diagram of a triangle and then projecting that using a projector of some kind or something to kind of project that onto the inside of the sphere. And the way that would get warped on the surface of the. Of the inside of the sphere such that the angles of that triangle would no longer add up to 90 degrees and they would be kind of.

The sides of triangle would be kind of curved and all that stuff. So I think there's. I did a little research and I found some who wanted to give him credit for being really the first to talk about a non Euclidean geometry. And I found others who were. Wait, is he right and what is he saying? Exactly. I found some paper that said in fact there's not even one consistent geometry to our visual field. It's even more complicated than that. Anyway, it gets crazy. So I don't know what the truth is, but very clearly what's going on in our visual field is very different than what it signifies to us.

13:25 Dylan: So I mean, I didn't go through it point by point for him to try to see. Oh, did he get all of the tenets of Lobachevsky and non Euclidean geometry, right or not. What I think is really, really clear is two things. One is, is that he is very clearly imagining a geometry that's distinct from Euclidean geometry based upon our visual field and going through a very precise thought process with exactly the example that you would give nowadays for how to understand it. What you're talking, when you talk about a triangle that has angles that adds up to more than 180 degrees, you give the example that Wes just gave.

You just spend a bunch of time imagining projections of 2D things onto the inside surface of a sphere as if you're laying on your back in a planetarium. And you just spend a lot of time imagining that. And to me, it didn't matter whether or not he got all of the details right such that you could derive all the self consistent axioms of such a geometry. The fact that he was thinking about it that way, I thought was just that blew my mind. I mean, just because I didn't know about it. I mean, to me, if you had asked me when did people start thinking about this, I would have said middle 100 years later.

And I'm not an expert on mathematical history or anything like that, but it was very surprising to me. And then the second thing was, is just that that was one example and he clearly meant to point to Euclidean geometry being one example of a self consistent geometry of which there could be n of them, there could be any number of them, and the spherical geometry one was one that was an example based on a visual field to point to the distinction between what we see and what we can imagine. And he's going down the road of, well, Euclidean geometry is part of, you know, a blind person could understand Euclidean geometry, right, because it's based upon a whole set of axioms.

And then that you could have another geometry that was based upon another set of axioms. That is also awesome and to me really, really foretelling.

15:40 Mark: Does that undermine his overall point though? That I thought it was just that you have this special geometry that we didn't know about of the actual appearances of the visual field and then you've got the tactile geometry. You know, we didn't read the section on touch, but he seems to think that when you feel, you know, a ball in your hand, you're getting the real figure, you know that you're getting the Euclidean figure. And so that is the one. And he spends quite a lot of time talking about how a blind person, you know, sort of Mary in the color room, but it's a Dr. Loeb was it a real person that he's referring to?

16:17 Wes: Dr. Saunderson.

16:18 Mark: So there's a blind geometer.

16:21 Wes: Yeah, yeah.

16:23 Mark: Could understand quite a lot by touch about how space worked such that the blind person could even get the idea of what the visual figure would look like. So this was kind of. I, I'm very surprised about this but I guess if there's an actual person and this is not just a Mary the color scientist made up example then yeah, okay, that person could get the idea that here is what the new dimensions would be. If I took this figure and I projected, I don't want to say an image but I somehow projected its outline upon a sphere, you know that that person could understand all this stuff. But I'm not seeing that the open endedness Dylan that you're seeing. It seems like if. Oh we don't even know what the real world is like. No we do know this like it's Euclidean. It's just that the apparent world, the visually apparent world relates to the tactile, the real world in this very predictable way.

17:20 Dylan: So I think there are both issues going on. I think there's the one between the tactile world and the. So he's making a distinction between the physical world in the world that is consistent within the mind and reason and that there's a distinction between those two things. And you have the visual world that you know the visual geometry was an example of that. But he also talks about Flatland two dimensional geometry and I guess I'd have to go back and reread it but to me this notion that there is a, that distinction between the tactile and the, the act of reason on it, the kind of language there.

Maybe I'm over reading into it right. Because of just him talking about multiple kinds of geometry and that there would be principal rules for those other geometries. Maybe I'm just extra sensitive to it because that's just the way in which mathematics works now. Right. And physics makes great use of the fact that there are many many kinds of geometry based upon. You define your geometry based upon a set of rules that govern that geometry.

18:26 Mark: So yes, it's the Idomenians he makes up this sci fi example that is like Flatland that is you know, for, for a being like this, if two objects, one is behind the other they wouldn't have the notion of a third dimension. So they would just say one has been overcome by the other whichever one that you overcome.

18:45 Wes: Quality of bodies. You know this is really interesting because this is true. This is one way we judge PERS perspective in depth. I went and looked at some, you know, some videos on YouTube about how all that works and things being in front of each other or behind each other. Right. The fact that we don't expect things to simply merge into each other is one of the important ways in which we judge one thing to be at a greater distance than another. It sounds simple, but when you think about it, it's kind of important. And yeah, if you're a flatlander, it's not the way it looks. Things just converge into each other and then come back out of each other.

19:23 Dylan: I mean, yeah, I mean, in particular, right. Besides the expectation that you can't have two things in the same place at the same time, you have to then have one in front of behind. You do have perspective where the height of the wall that's closer to you is going to be taller than the one behind it. And so therefore that would be part of the visual and field information that will allow you to say, well, one's moving behind, you know, one truck is moving behind the other truck because the truck forward of it is taller in your visual field. But at Flatland you won't get that right, because you won't have that third dimension.

19:58 Mark: So it is true that if we had different senses like these two dimensional seeing creatures do, then we would have a different, yet a different geometry to characterize the appearances. And I think this is getting at again what we've been saying. Reid's overall point is of how different the appearance can be from the reality. But it's not, I think, saying, but the reality could be any geometry at all. Like the geometry. The reality, I think, according to Reid, is what even the flatlanders, if they were careful enough, they might be able to derive that.

Oh, let's. Maybe there is another dimension that we're not able to see and maybe we could even do that and come up with future things, but we would be getting at greater and greater reality that God, right, does not fool us into giving us a bunch of bullshit that has, you know, we, we get these systematic relations between the appearance and the reality and that we rely on that to truly know the reality.

21:02 Dylan: Yeah, I wasn't implying that there were multiple geometries for reality necessarily at all. I was saying that the notion of a geometry is distinct from what the world. There are multiple geometries that could be at play, just that notion that there is something more than just Euclidean geometry and that the only geometry you would have would be the one that corresponds to the world that is, I think, pretty awesome.

21:27 Seth: Yeah.

21:28 Dylan: And I guess I'll just say in my thinking it's so awesome might be clouded by simply the fact that I don't know enough mathematical history, but I found that pretty amazing.

21:41 Wes: So he's a realist in spite of all of this.

21:44 Dylan: Yes.

21:46 Wes: And he knows that he doesn't have an argument against the skeptics really. Right. He can't go to the sixth skeptic and say I can prove to you that the way we are naturally constituted to read these sensations so as to signify X I'm this external reality that there's no proof that that puts us in touch with the really real, with things in themselves. But nature did make us such that we habitually do that. And it is very useful to think that way. And so there's no knockout anti skeptical argument here. But he can point to the fact, I mean, well, maybe there are some more subtle arguments about the self limiting nature of skepticism.

22:38 Dylan: You're right, he has a sense of futility in this aspect of like I'm not going to be able to prove it to you, but he's saying that laws of nature. And he's pretty general about what he means that I mean, he means like for instance, the constitution of our, the relation of our mind to the processing of our visual stimuli are laws of nature. Right. And it's not just, you know, F equals MA and stuff like that and that those laws are really correspondences between cause and effect and how we make our way through the world and understand make decisions because those decisions really rely on causes resulting in effects. And our judgments of those are given by the way the world works and our senses give us ways to determine them, whether explicitly or implicitly.

23:31 Wes: He likes this analogy to the natural language of facial expressions and body language and vocal intonation and the way in which we can use that to read the minds of others in the sense of what is their, was their mental state, what is their effective state? So a certain facial expression connotes anger to us. Right. And we are just automatically. And it's cultural universal and we are automatically primed. We don't even think about it. We look at the expression and we see anger. So we take a. It's a signifier that evolution has kind of hooked up to the emotion and it becomes a way of communicating.

So it's a natural language. And yet, you know, we could pretend like we're skeptics about that. We could say, well, there's nothing inherent. And you know, this is like These things are arbitrarily put together, but they were put together by evolution, which of course he's not thinking about. He simply refers to the way nature has constituted to us. These things are hardwired into us and there's a lot to be said for that. So there's a lot to be said for that when it comes to interpreting facial expressions. And there's also a lot to be said for that when it comes to having certain data in one's visual field and then seeing through to that to a signified three dimensional reality.

And idealists like Berkeley. Well, I don't know what Berkeley would say exactly about this, but I'm trying to express the fact that he's, I think the average philosopher and inclined towards phenomenalism would think, well, the things in themselves are actually inaccessible because all we have access to our own mental states. But I think he's doing something very clever by saying, well, our relationship to things in themselves is not a relationship of sensory access. Exactly. Even though the senses are important for that. It's a relationship of signification.

We can refer to them, we can think them. And there may be a way of saying, well, we do in some sense have an immediate access to reality. That way it's not immediate sensory access, but it's immediate. What? It's knowledge, it's non knowledge, some of

25:41 Mark: it is natural knowledge and some of it is acquired knowledge. Yes, as he's going to get into.

25:46 Dylan: So can we characterize, Maybe this is the response to the skeptics or maybe there's something more to characterize about overall Reid's beef with someone like Berkeley or the idealists. Is there something different to say about it than just they're coming to an absurd conclusion in their idealism and we should shrink away from that? I mean, that's one of his arguments. You know, your conclusion is so absurd that you should understand that it's stupid. But is there something else about the characteristic of where idealism is going wrong and the kinds of answers to the kinds of questions it's asking about the world and the relationship of what we're experiencing and what the world is and how our minds are interacting with the world, or is it just the terms of the answer are so absurd that we should reject them?

26:47 Mark: I mean, that's what he says most of the time I haven't thinked about Berkeley, but. Go ahead, Wes.

26:52 Wes: Well, he is actually a big fan of Berkeley.

26:55 Dylan: No, he's a big fan of all of them.

26:57 Wes: He's like, yeah, but especially Berkeley. And I think Because Berkeley is the one kind of Berkeley has keyed into the essential point, which is this dissimilarity between sensation and reality. Berkeley just draws the wrong conclusion from it. Right, because he'll say that they're operating made this huge advance over the ancients. Because the ancients just thought, okay, in a very naive, realist way, at least the Aristotelians, our perceptions are just imagistic copies of reality. And so the early moderns figured out that that's not the case.

But they held on to a premise of the ancients, which made it even worse for them. And the premise they held onto is that access to reality has to be mediated through resemblance. And that's what he wants to get us away from. And Berkeley starts us down the road, even though he takes a real wrong turn. But Berkeley ingeniously shows us the ways in which our access to reality cannot be mediated by resemblance.

27:59 Mark: Yes, well, so, right. The general critique of Berkeley, as you were just saying, retains the idea, really. He doesn't have Hume's notion of cause and effect.

28:09 Seth: Right.

28:09 Mark: Hume's notion of cause and effect is just that, it's patterns that we don't understand. So earlier, Dylan, you said something like, you know, we have to see that these laws of nature are matter of cause and effect. Whereas I think he actually, in the chapter 20, he, Reid, says effects and causes in nature mean nothing but signs and the things signified by them. So we do not perceive efficiency in natural causes, we don't see powers. So this is straight from Hume. Whereas Berkeley thought with the ancients that if something has a cause, an effect must have a cause.

That's enough like that effect that it could produce that effect. Right. And Descartes had stuff like, well, it has to have at least much reality in the cause as in the effect. He just was importing all these things from the peripatetics and so thought that since the image of something that we have is so different from the physical thing itself, then there couldn't possibly be a causal relationship between them. That's just not how causality works. It has to be. Only an image can cause another image. Only an idea can cause another idea. So therefore physical things, the world, have to be ideas if they cause ideas in our heads.

So that's right, exactly. The Reid is saying, no, no, no, there is a correlation, a signifying relationship between the ideas that we have in our heads. He doesn't even call them ideas, but the images and the things themselves. And those are quite different, as Berkeley has pointed out. But there's just a brute correlation between them and that's just what we're given by. You know, there are limits to our understanding.

29:40 Wes: Yeah. So for those of us who've at one time or another been impressed with Kant and the idea that we have this immediate access to phenomena as we construct them, but things in themselves are tragically and forever cut off from us. You know, we're sort of, I think, at least to me, what has been attractive about that idea is that it kind of doesn't make any sense to say that we can have access, any sort of immediate access to things in themselves because that access is always relational. This is kind of evocative of the beginning of Hegel's phenomenology because it's always a subject object relation, it's always mediated.

And because it's mediated, it's always distorted in some way by ourselves, minds. But I think what Reid is pointing to is the complaint really comes down to the idea that, well, my phenomena as I construct them, my mental representations can't adequately represent things in themselves because they can't be copies of them because they can't look like them. And that's true, but that turns out not to be the point. We don't need one to look like the other for it to give us access to it. I think that's a mind blowing idea. And I just, I don't see that widely represented in a lot of the, even contemporary analytic philosophy that we've read.

I don't, I don't know that I've ever seen it put so well and so clearly. Am I overstating this or am I.

31:07 Dylan: No, you're not. And this is to me a good way to frame the answer to what I was asking about, what goes wrong. So one of the things that goes wrong or the critique of someone like Reid has to do with the terms under which we understand access to things in themselves. So one way of characterizing some big chunk of the portion of the history of philosophy, certainly all of the hand wringing from Berkeley, Hume, Kant, Descartes, all the way down, is how do I get to know the truth of the world based upon understanding and having access to what it is, the thing itself, and then different ways of parsing out that problem based upon the fact that we come up with examples where we clearly aren't seeing what it is.

Right. And Reid, I think, as you described, has some of the clearest answers to why you don't have to have the answer to that question on the terms that you think you need to have it in order to still have the world out there and have your perceptions have real meaning. And in a way, he's saying you do it all the time. Right.

32:18 Seth: Not only do you do it all the time, the only time you don't do it is when you're doing philosophy. And you couldn't do philosophy if you didn't already do it.

32:31 Dylan: Yes.

32:32 Wes: Right.

32:32 Dylan: Yes.

32:34 Seth: Because he'd mix that analogy between sensation and language. He's essentially saying if you can't experience the world veridically, then you have nothing upon which you can base the development of your consciousness and your experience to the point where you could even ask these kinds of questions.

32:53 Mark: Sounds pretty nyaya to me.

32:55 Seth: I was thinking the same thing.

32:57 Wes: One of the interesting things about all of this is the way in which we get spatial information about the world. Right. And we get them through two senses, according to him, through touch and through sight. But it turns out importantly that spatial information is not sensory information, even though we rely on sensory information to construct space, let's put it that way. Although construct. Right. For him can mean just get. Means we're constructing it, but it could mean we're getting direct access to a thing in itself. It's not prejudiced towards distorting reality. But so we're making a jump.

33:34 Mark: So we're. Yeah, we're not constructing, we're making a jump. We are. Our mind is led.

33:39 Wes: Inferring, or as he says, you know, we're inferring or getting at the signified.

33:43 Dylan: But our minds are inherently interactive with this process. Right. There's processing that happens.

33:50 Mark: Yeah. I don't even want to say infer, because that sounds like reasoning, but go ahead.

33:53 Seth: Right.

33:54 Wes: So we instinctually, unconsciously, infer process whatever it is that gets us from the signifier to the signified. Yeah.

34:02 Dylan: The laws of nature, of mind.

34:03 Wes: Construct, I don't think is a bad word as long as we understand what. What we mean by. So space is not an object of sensation, and spatial information is not an object of sensation, which is not itself a new idea. Right. Hume is onto this, just like causality and Kant is onto this. Right. Causality and space kind of fall. Get. And everything else fall under the same category, which is to say they can't be sensory objects. They can't come in through the manifold. And so in a way, it looks like they have. Like they have to be imposed upon the manifold.

But going beyond that, one other very ingenious thing about Reid is he understands that there's a sense in which sight is Only accidentally. Sight and touch are really only accidentally related to spatial information. We've been, we ourselves have been so constituted that they allow us sight and touch, allow us to infer spatial information. But it need not have been that way. And this will sound really confusing, I think to some readers, but a certain point he said, well, you know, it could have been hearing, it could have been another sense that does this.

There's no reason why hearing couldn't be made the sense that conveys spatial information. Then you'd think like, what, what are you talking about? Right? Space is something, you got to see it or touch it.

35:14 Mark: Do you know what it's like to be a bat, Wes?

35:16 Wes: Right. But it made me think about things I'd read in various neuroscience books or articles. So for instance, some blind people do see by echolocating. So some just, even without even being trained will start to do clicking as kids and can basically construct a three dimensional, like an image of three dimensional space around them. And it's the same part of the brain, the same, you know, visual cortex processing goes on as if it were coming from the eyes. Now it's a very low resolution image echolocation. And of course it's not, there's no color.

35:51 Mark: But Daredevil has color calling.

35:54 Wes: It's not just analogously an image. So the, the brain actually doesn't care where it comes from. And the same thing, they've done experiments where they put a photosensitive patch on someone's back and then that patch will translate the effects of light into certain stimulations on the skin. You can see with your skin, give it enough time. You're visual cortex just latches onto that. What it cares about is that, oh look, there's spatial data patterns going on there. I'm going to latch onto that, I'm going to use it so you can actually see through your skin. So I don't know, is this helping? Am I just.

36:31 Dylan: It is helping.

36:32 Wes: I just find it really amazing.

36:33 Dylan: But you're digging into, you know, a part that I wondered about. I mean, it makes sense that we get our, we build our three dimensional world through information, through the visual primarily. And it also makes sense that it's sensible that that's working through a particular area of our brain. And then you're pointing out that we know that we can process other information in order to develop those three dimensional kind of positions and stuff. I did wonder about even hearing and smell because you know, we have, at least with hearing we have stereo ears just like we have stereo eyes and we can tell when sounds come from different directions and further away and closer by based upon getting Doppler effect and other kinds of positional information.

And someone who has good sight, I'm sure, unless they really train themselves, you know, don't have the kind of resolution that you can get out of your ears. But most people still get direction out of their ears and even out of smell. Right. I mean, it's even lower resolution, but just you can tell where a smell is coming from. It's not like it just has no direction or no pointing to things. You can go, just like a dog, you can go find something based upon smell.

37:54 Wes: Yeah. He does make the claim that smell and hearing don't carry any spatial data with them.

38:01 Mark: Right.

38:01 Wes: Which. Which sounds weird because of course, we all know that we can tell where a sound is coming from. But I think he means. I think he was thinking in more robust terms of there's not enough spatial data to construct any sort of. That's a sphere spatial image. Yeah. An image of one's spatial environment. And it turns out he's wrong. Right. Because of echolocation. And. And even I think for blind people who don't echolocate, I wouldn't be surprised if the visual cortex is involved in processing some of the auditory data that gives them a sense of their surroundings.

So, for instance, at Harvard, I actually had a blind girl ask for help finding a building on Harvard Yard. Normally, there wouldn't be a problem, except Harvard Yard is this big open space, and so there's not enough bouncing of sounds. It's just too big and open to be used. You know, it's confusing, right? There's not enough resolution. And at a certain point as we were approaching the building she wanted to find. She's like, oh, I can hear where I am now. I don't need your help anymore. I can hear where I am now. And I think one might think, well, that's just an.

Being used analogously, but I don't think so.

39:05 Dylan: I think I agree.

39:07 Wes: Yeah.

39:07 Mark: I'm sure there are other instances of this in the media. But, like, I don't know if any of you sat through any of that daredevil TV show that was in Netflix. I did, yeah. Because they would be like, he's constructing his world out of smell and hearing and even taste. But of course, they have to show it to us as this weirdly colored, you know, like, seeing through an infrared camera or something. Like, it's like sight, but it's different because we're.

39:33 Seth: We're.

39:33 Mark: Now we Just have to use our imagination to picture the thing that's being presented. Imagine this was a field of space constructed from smell and hearing.

39:43 Wes: Right. And I think we could say. And this is like the. What it's like to be a bat joke you made, Mark. I think, yeah, in a way, we're not that far off. Right. Echolocation is just very low resolution site. Right. So it's like, okay, imagine what it's like to see. And now imagine lower resolution, like being in a. In a very dimly lit room or any other way you want to do it. And there you go. Now you know. Now you know what it's like.

40:08 Mark: Well, another thing about the bats related to one of these whole chapters was that is that they hang upside down. Do they see it as upside down? It doesn't bother them. At least they're not discombobulated. They're not just like, who's that? Is that Jim? Wait, let me get right side up again. And. Oh, no, no, that's. And then I'll hang back up. So there. They seem okay with it either way. This was just one of the things that was asked in the chapter of like, okay, well, philosophers, anatomists have discovered that on the retina, the image is actually upside down.

So do we conclude from that? How do we get the image right back, right side up? And one of the things that had been put forward is, well, we just sort of infer that, well, it can't be upside down. It can't be like. And he's saying, no, we don't see that image at all. Only the anatomist sees that image. The fact that it's on our retina doesn't mean we see it. It, you know, gets converted to something that gets put down the optic nerve. Of course, now we have all these other models. Like, yeah, images can get moved through a fiber optic cable. Like, it doesn't matter that the data does not resemble the image.

The image could still somehow be encoded and then flipped it. So I don't know that he's actually solved the problem. Clearly that data from the retina gets to us is encoded somehow. That resemblance is maybe not the best word, but encoding is. Like, isn't encoding a kind of resemblance?

41:31 Dylan: Well, so that question, I think, is pretty pregnant. Why would we say the access that Reid is describing through many steps, why do we want to say that's not resemblance? At some level, there has to be something like resemblance. When we talk about the steps we go through to get to what the thing is, right, we're processing, you know, not any different than if I look at a electrical signal on an oscilloscope. It has a resemblance to that electrical signal. It's not the electrical signal itself.

42:07 Wes: I think the idea is that. Yeah, brain activity does not resemble.

42:11 Dylan: Yes.

42:12 Wes: Well, the things that it's so. And he says this directly so you. Right. So there's an image on the retina, and then the very center of the visual field is focused on what's called the fovea. So very. A point that's very packed with cones, Right? There's rods and cones, rods for black and white site and then cones for color. And they're most densely packed right at the very center of the field of vision, which is when things get kind of blurrier and less distinct as we go right out from the very center of our field of vision, which is one reason why it's upside down on the retina, because it has to be focused through a lens. And focusing it through the lens flips it upside down. There's a lot of.

42:53 Dylan: We just have one stage of focus. We don't have a double stage. We don't have a compound eye, so.

42:58 Seth: Well, we do.

42:59 Wes: I mean, there is. Yeah. So there's the cornea and then there's the lens. There's pre pupil refraction and then there's post pupil refraction. So there isn't a way of double focusing. But anyway, the point is that. Right. So what is the light hitting on the back of the eye? On the retina? And if I looked at eye anatomy in preparation with this episode and I realized. Well, I didn't really know much about that either and how crazy that is. The eye by itself is like something out of an alien movie or something. But so what happens to that light hitting the back of the retina?

Well, there are these neurons there that immediately take it up and turn it into inputs. It's much more complicated than that because there's color and all sorts of things going on. It gets routed through, like, the hypothalamus and then to the visual cortex. But, yeah, there's no way to say that once it gets pumped into neural processing that anything that it's doing that there's. That there's a resemblance between what was on the retina or what's out there in the world and between what's going on in the nerve fibers. It's now just abstract information.

44:05 Mark: Right, Abstract. So one way of interpreting resemblance is not just like what looks like it resembles to us, because even that's a little subjective.

44:13 Wes: Right.

44:13 Mark: Because Berkeley was saying, oh, that you know, the image that you might have of the glass is not the same as the physical glass.

44:21 Wes: Okay.

44:21 Mark: But there is a symmetry or what's the. There's a conformity, you know, a correlation between the left part of the glass and the left part of the image of the glass and the right part of the glass and the right part of the image of the glass. You know that you have these. A structural isomorphism. That's what I'm looking for. So in any encoding you would have to have some sort of. Okay, well, this part indicates. It is the encoding of that part of the glass so that then an image could be reconstructed in our imagination or however it is we somehow gain the knowledge, we somehow have the sensation of an image. At least, you know, in the case of sight. Somehow this.

44:58 Wes: Right, yeah.

44:59 Mark: So somehow. So the simplest explanation would seem to be that, yeah, that image on the retina does somehow get pretty much taken the way it is on the retina through the tube. And you know, he specifically says it's not. He calls it the sensorium. But this is what Dennett had called the Cartesian theater. That, you know, it's not the case that like, oh, the mind sees the image that's in the head. No, the mind just has the image. Because otherwise, if the mind sees the image, what does the mind have?

45:31 Wes: Eyes.

45:32 Mark: What's the anatomy of the mind's eyes like?

45:34 Wes: It would, in a way, very similar to Dennett. Yeah, he argues against that sensorium, Cartesian theater idea.

45:39 Mark: Yeah, but it's still, it's not merely magic. It's not merely that there's no correlation between the idea, the visual idea that we have in our head and this actual image that is on the retina.

45:50 Dylan: Well, you.

45:51 Wes: We're talking about three many things here. We're talking about reality and then the image on the retina and then brain activity and then the images in our minds. And so yeah. Can brain activity quote, unquote resemble the image on the retina? Can our, the idea in our mind, quote, unquote resemble? I don't think resemble is going to turn out to be the right word. I think that's part of the point. Right. That he's making.

46:17 Mark: If it just means in code, then that's my challenge.

46:19 Seth: That.

46:20 Mark: Yeah, actually it could resemble as to the thing out in the world. So this is actually his.

46:25 Wes: I think signify, though, is a better. Yes, that's the one he wants. But yeah, go ahead.

46:30 Mark: I'll save my other point about Berkeley for The beginning of part two. Please come back next week. Go to partiallyexaminedlife.com support if you want your part two sooner than you might otherwise get it. Otherwise, we'll see you later. Thanks for listening.

46:44 Dylan: Thanks.

46:45 Seth: Thanks.

46:46 Dylan: Thanks.