— The Great Whatever

]Hmm. Why does Sellars think this? — tgw

Here, I'll take a swing at it. I think Sellars means something like this:

"I had experience x."
"I had experience x, and it was veridical."
If the former is the same as the latter, then the second clause in the second statement is vacuous and veridicality adds nothing to the discussion. If, on the other hand, the second clause in the second statement is not vacuous, then these are two different statements. It follows that "Having a veridical experience of P" is something over and above "Having an experience of P." But this implies that veridicality is "optional" - it makes sense to speak of the experience as lacking veridicality. — Pneumenon

]That can't be right, though, because the sense datum theorist doesn't claim that all things of the form 'I had experience X' have no duality between veridicality and non-veridicality, only that there's a certain class of experiences that it makes no sense of to call non-veridical. — tgw

I think the key is to focus on why Sellars' sense theorist is honing in on this special class. For these theorists, its meant as an solution to a problem: If there is no way to determine whether an experience is veridical or non-veridical, then how can knowledge get off the ground? So a class is identified where it is possible to make such a determination. And so we have a foundation on which we can build.

But how can we can move from knowledge gained from necessarily veridical experience to knowledge involving potentially non-veridical experiences? That's the rub.

The experience of non-veridicality precedes the idea of veridicality. The very idea of veridicality would be meaningless if we hadn't already experienced being wrong. (it's an anstoss type of logic.)

The necessarily veridical class of experiences operates on a pre-having-experienced-being-wrong level. It doesn't leave that level because it can't leave that level. But, by that same token, it can't shed any light on anything outside its own class. The veridicality of experiencing e.g. a red triangle is a closed loop.

I think Pneumenon's analysis is more or less right. The sense datum-theorist does indeed hold on to the veridical/non-veridical distinction - but the logic of the class to which that distinction applies, simply does not apply to the class of the 'necessarily veridical.' Apples and oranges.

Another way to put this is that the very idea of a necessarily veridical class can only be a backwards projection by someone who has experienced non-veridicality. If they had always remained within the purely veridical, they could never do this. It would be like the fish who doesn't know what water is.

Or, to use Hegelian language: the class of necessarily veridical experiences is only veridical for someone steeped in non-veridicality. In-itself (and it's precisely this in-itself the sense data theorist is trying to leverage) it's neither nor.

Also, by the by, I don't know how much everyone's read ahead, but Sellars is super clever (I think the dude's actually internalized his Hegel. Was anyone else doing that in his milieu?) This essay straight up blossoms and it blossoms just where you want it to (so, for instance, the illustration of the clerk in the neck-tie shop, or whatever, touches on exactly the issues we're all discussing now.)

The experience of non-veridicality precedes the idea of veridicality. The very idea of veridicality would be meaningless if we hadn't already experienced being wrong. (it's an anstoss type of logic.) — csalisbury

I don't know, why? I think it's a coherent position to say that there are no non-veridical experiences, even if there are veridical ones. We might draw certain inferences or get certain expectations from veridical experiences that are unlicensed, and so have our expectations disappointed, but the issue with non-veridicality seems to be that realist assumptions about perception engender their possibility, not that we learn about non-veridicality from experience and so project veridicality back onto it.

The sense datum theorist seems to me to be seeking a realm in which act and object unite, making realist metaphysics of perception irrelevant, and hence the notion of non-veridicality that accompanies it. It always seemed to me that skeptical arguments about non-veridicality are only coherent, and are meant to be, in response to realist assumptions.

Veridicality doesn't seem to hinge on this – what you see is what you get.

--

Although I will say that the objection as Sellars outlines it -- that empirical knowledge can't rest on a secure foundation if it must come from a class of things that has non-veridical members that can't be distinguished surely by any mark -- presupposes that in order for knowledge to have a secure foundation, there must be a sure way of knowing that one knows in any particular case. But this just doesn't follow if we're interested in knowledge, not knowledge of that knowledge. It might be that we know all sorts of things, even if for any particular case we can't infallibly (or even reliably!) know that we know this.

@The Great Whatever

I don't know, why? I think it's a coherent position to say that there are no non-veridical experiences, even if there are veridical ones. We might draw certain inferences or get certain expectations from veridical experiences that are unlicensed, and so have our expectations disappointed, but the issue with non-veridicality seems to be that realist assumptions about perception engender their possibility, not that we learn about non-veridicality from experience and so project veridicality back onto it.

That's fair. Then realist assumptions themselves would be a reaction - a theoretical reaction - to disappointment. But, then, veridicality is meaningless without a minimal helping of realism. What does 'veridical' mean if not that the way things seem (or appear to be) coincide, in this case, with how they are.** If seeming and being are one and the same, then the very idea of veridicality is meaningless. (But then, to deal with the fact of disappointment, we would have to substitute a different kind of thinking, where the distinction would not be between seeming and being, but between valid expectations and invalid ones. And then, once again, my indisputably experiencing a red triangle would have no bearing on whether or not any corresponding expectations were valid or not.)

**Sellars, in a later section of this essay, gives an analysis of seeming/being that I find very satisfying.

Veridicality doesn't seem to hinge on this – what you see is what you get.

But the whole thing with veridicality is that what you see might not be what you get (i.e. you might be wrong.) If you can't be wrong, then you'll always get what you see, and you won't even comprehend the idea of that not happening.

Although I will say that the objection as Sellars outlines it -- that empirical knowledge can't rest on a secure foundation if it must come from a class of things that has non-veridical members that can't be distinguished surely by any mark -- presupposes that in order for knowledge to have a secure foundation, there must be a sure way of knowing that one knows in any particular case. But this just doesn't follow if we're interested in knowledge, not knowledge of that knowledge. It might be that we know all sorts of things, even if for any particular case we can't infallibly (or even reliably!) know that we know this.

But the reason we want to know that we know isn't that we're interested in any sort of meta claims. It's not even (at least not at first) a cartesian defense against an evil demon. It's that we thought we knew, but we turned out to be wrong. We thought we knew, but we didn't. So then: how do we know whether we really know? Of course, we'll never be wrong about having seen a red triangle, or experiencing an emotional or spiritual movement while listening to song x. But we may be wrong such that e.g. the rocket we engineered to get to the moon can't even get out of earth's atmosphere. In any case, Sellars is subtle (or at least cautious here.) As you've mentioned he's talking from the sense-datum theorist's point of view, and it's the sense-datum theorist who is hunting for something that we know that we know, and therefore honing in on this class. But even if we disagree with the conclusions of the sense-data theorist, I think one can see where they're coming from.

Also, by the by, I don't know how much everyone's read ahead, but Sellars is super clever (I think the dude's actually internalized his Hegel. Was anyone else doing that in his milieu?) This essay straight up blossoms and it blossoms just where you want it to (so, for instance, the illustration of the clerk in the neck-tie shop, or whatever, touches on exactly the issues we're all discussing now.) — csalisbury

My opinion of the essay so far is that it's horribly written, but then I again, I hate Hegel. He's not quite as garbage as Heidegger, but he's not far from it.

The experience of non-veridicality precedes the idea of veridicality. The very idea of veridicality would be meaningless if we hadn't already experienced being wrong. (it's an anstoss type of logic.) — csalisbury

I don't buy that. I think that would only work if one thought that veridicality were necessarily the case. One could believe that veridicality is contingent instead, and that one's sense data haven't happened to be wrong yet, while one could still imagine the possibility.

Another way to put this is that the very idea of a necessarily veridical class can only be a backwards projection by someone who has experienced non-veridicality. — csalisbury

Why couldn't someone who believes that sense data are necessarily veridical have the view that non-veridicality isn't even coherent, for example? In that case, it would be dubious to say that they've experienced something non-veridical.

But, then, veridicality is meaningless without a minimal helping of realism. — csalisbury

That was my immediate thought in response to that, too, but then this struck me: why couldn't it be the case for an idealist (an idealist who adheres to a sense data view in this case) to believe that their sense data could fail to correspond with ideal existents? The only thing that a veridicality/non-veridicality dichotomy requires, logically, is that one's sense data (or one's phenomenal experiences on a view like mine) (a) don't exhaust the world ontologically, and (b) ostensibly have some sort of correlation to things that aren't one's sense data or phenomenal experiences.

As you've mentioned he's talking from the sense-datum theorist's point of view, and it's the sense-datum theorist who is hunting for something that we know that we know, and therefore honing in on this class. But even if we disagree with the conclusions of the sense-data theorist, I think one can see where they're coming from. — csalisbury

It's extremely dubious that any sense data theorist would say both that (i) there are both veridical and non-veridical sense data, and at best we have methods of knowing that some sense data are more reliable than others, and (ii) they're forwarding sense-data theory in a bid for epistemic certainty.

Earlier on, I said this:

You're saying that, if claim A is solely about experience B, and claim A is solely grounded in experience B, then A can't be non-veridical. That is to say, if I have experience B, I can't infer a falsehood about experience B solely from that experience. Do I have you right, or at least, mostly right?

I see a red triangle. Upon seeing it, I form the belief, "I am currently having the experience of seeing a red triangle." What is necessarily veridical here? Following the above quote, the necessarily veridical thing must be my belief that I'm having that experience. Which means that there's no room for error in the process of my forming a belief about an experience that I'm having, provided that that belief is solely derived from that experience.

Now, we want to say this: "For this class of beliefs, it makes no sense to say that they are non-veridical." We're not just saying that all such beliefs are veridical, but that it it is senseless to talk about them any other way. If this is true, then it must be logically necessary for those beliefs to be veridical, which is to say that "A belief of this class is non-veridical" must imply a contradiction. (You can substitute "claim" for belief here, if you like - I think TGW used that word a few pages back)

It seems to me that the most obvious way to get this result is to say that the experience in question is identical to the belief. My belief that I am currently having the experience of seeing a red triangle must be that experience. If you didn't want to say that, I guess you could appeal to an infallible belief-forming faculty.

Thoughts, anyone?

I see a red triangle. Upon seeing it, I form the belief, "I am currently having the experience of seeing a red triangle." What is necessarily veridical here? Following the above quote, the necessarily veridical thing must be my belief that I'm having that experience. Which means that there's no room for error in the process of my forming a belief about an experience that I'm having, provided that that belief is solely derived from that experience. — Pneumenon

We just had a big discussion about this in the thread about whether we can be mistaken about any experiences . . . let me find it to give you a link:

http://thephilosophyforum.com/discussion/917/can-we-be-mistaken-about-our-own-experiences#Item_254

You could get a belief about an experience (a phenomenal experience that is) wrong if the belief and the phenomenal experience aren't both presently occurring--you could remember it incorrectly, for example.

However, Sellars' comments about veridical and non-veridical sense data aren't about this to my understanding. The idea is that sense data are getting something else--whatever is causing them, where we're not directly aware of what's causing them--right or wrong. Of course, talking about sense data in that way, it's unclear why we'd be supposing that any(one is saying that any) sense data are or can be necessarily veridical.

So then: how do we know whether we really know? — csalisbury

We don't; but then, epistemologists usually don't frame the question this way, but rather in terms of 'Do we know?' or 'how do we know?' Some sort of sliding happens between knowledge and knowledge of knowledge (some people even think the so-called 'KK' principle is valid).

Any way you slice it, the 'figure' of the sense-datum theorist, in Sellars' essay, is seeking foundational experiences - experiences which, unlike other experiences, can be determined to be veridical (whereas the others have no 'inspectable hallmark'). The point of this 'figure' is represent a way of thinking which Sellars is going to go on to criticize. (And, without saying I agree with it, I think 'knowing that we know' is an understandable approach, tho I'm not familiar with the literature on the 'kk' principle.)

But maybe we're on the same page here, and I misread your intent in raising the point about knowledge of knowledge.

It seems to me that the most obvious way to get this result is to say that the experience in question is identical to the belief. My belief that I am currently having the experience of seeing a red triangle must be that experience.

Yes, I think Sellars says something similar.

Now it might seem that when confronted by this choice, the sense-datum theorist seeks to have his cake and eat it. For he characteristically insists both that sensing is a knowing and that it is particulars which are sensed. Yet his position is by no means as hopeless as this formulation suggests. For the 'having' and the 'eating' can be combined without logical nonsense provided that he uses the word know and, correspondingly, the word given in two senses. He must say something like the following:

The non-inferential knowing on which our world picture rests is the knowing that certain items, e.g. red sense contents, are of a certain character, e.g. red. When such a fact is non-inferentially known about a sense content, I will say that the sense content is sensed as being, e.g. red. I will then say that a sense content is sensed (full stop) if it is sensed as being of a certain character, e.g. red. Finally, I will say of a sense content that it is known if it is sensed (full stop), to emphasize that sensing is a cognitive or epistemic fact. — Sellars

To sense a red triangle is to know that triangle as red.

This stipulated use of know would, however, receive aid and comfort from the fact there is, in ordinary usage, a sense of know in which it is followed by a noun or descriptive phrase which refers to a particular, thus

Do you know John?
Do you know the President?
Because these questions are equivalent to "Are you acquainted with John?" and "Are you acquainted with the President?" the phrase "knowledge by acquaintance" recommends itself as a useful metaphor for this stipulated sense of know and, like other useful metaphors, has congealed into a technical term. — Sellars

Why couldn't someone who believes that sense data are necessarily veridical have the view that non-veridicality isn't even coherent, for example? In that case, it would be dubious to say that they've experienced something non-veridical.

I think the answer to this is pretty straightforward. They've experienced something that seemed to be one way, but was actually another. Non-veridicality is coherent precisely because we understand the difference between seeming and being. A sense datum, on the other hand, would be necessarily veridical because its seeming is its being (but, again, this would seem to make the veridical/non-veridical distinction itself inappropriate to it.)

That was my immediate thought in response to that, too, but then this struck me: why couldn't it be the case for an idealist (an idealist who adheres to a sense data view in this case) to believe that their sense data could fail to correspond with ideal existents? The only thing that a veridicality/non-veridicality dichotomy requires, logically, is that one's sense data (or one's phenomenal experiences on a view like mine) (a) don't exhaust the world ontologically, and (b) ostensibly have some sort of correlation to things that aren't one's sense data or phenomenal experiences.

Sure, but, with that kind of idealism, we'd have to posit a bigger mind (like God's) that grounds the objects we, finite minds, only see through a glass darkly. This kind of idealism isn't ultimately all that different from realism - both deal with objects 'out there' we have limited access to.

It's extremely dubious that any sense data theorist would say both that (i) there are both veridical and non-veridical sense data, and at best we have methods of knowing that some sense data are more reliable than others, and (ii) they're forwarding sense-data theory in a bid for epistemic certainty.

But it's not veridical and non-veridical sense data - it's veridical and non-veridical seeings. Or seeings and ostensible seeings. (this is the same point you made above, to Pneumenon "The idea is that sense data are getting something else--whatever is causing them, where we're not directly aware of what's causing them--right or wrong."

So, then, the story goes, the Sense data theorist moves on to this:

The idea springs to mind that sensations of red triangles have exactly the virtues which ostensible seeings of red triangular physical surfaces lack. — Sellars, outlining the sense data theorist's course of thought

---------------

Of course, talking about sense data in that way, it's unclear why we'd be supposing that any(one is saying that any) sense data are or can be necessarily veridical. — Terrapin

Right, that's Sellars point!

they must overlook the fact that if it makes sense to speak of an experience as veridical it must correspondingly make sense to speak of it as unveridical — Sellars

I think the answer to this is pretty straightforward. They've experienced something that seemed to be one way, but was actually another. — csalisbury

That would explain why someone who thought that experience was (necessarily) veridical could come to think otherwise.

That's not what I'm addressing here by this though: "Why couldn't someone who believes that sense data are necessarily veridical have the view that non-veridicality isn't even coherent, for example? In that case, it would be dubious to say that they've experienced something non-veridical."

What I'm saying is that it's a logical possibility that Joe, say, believes that sense data are necessarily veridical, where Joe is saying something about sense data correlating with existents that are not themselves sense data, and where Joe has a view that non-veridicality isn't even coherent. That's a logically possible stance for someone to have.

A sense datum, on the other hand, would be necessarily veridical because its seeming is its being (but, again, this would seem to make the veridical/non-veridical distinction itself inappropriate to it.) — csalisbury

I agree with that--that it wouldn't make sense to even talk about the distinction if we're simply talking about sense data with respect to itself. For that reason, I don't believe that Sellars is talking about sense data in that sense when he discusses veridicality versus non-veridicality, because the distinction wouldn't make sense in that case.

Sure, but, with that kind of idealism, we'd have to posit a bigger mind (like God's) that grounds the objects we, finite minds, only see through a glass darkly. This kind of idealism isn't ultimately all that different from realism - both deal with objects 'out there' we have limited access to. — csalisbury

Yeah, they're similar in that respect, but still one is idealism and the other realism, because one posits that only mental things exist (or can be known if it's just epistemic idealism), whereas the other posits that non-mental things exist (and perhaps can be known).

But it's not veridical and non-veridical sense data - it's veridical and non-veridical seeings. — csalisbury

But wait though. Sellars says for example, "The first idea clearly arises in the attempt to explain the facts of sense perception in scientific style. How does it happen that people can have the experience which they describe by saying "It is as though I were seeing a red and triangular physical object" when either there is no physical object there at all, or, if there is, it is neither red nor triangular? The explanation, roughly, posits that in every case in which a person has an experience of this kind, whether veridical or not, he has what is called a 'sensation' or 'impression' 'of a red triangle.'"

The part I emphasized is a description of sense data. "Whether veridical or not," then, is about sense data in this passage (per the explanation of sense data theorists which he's going to be addressing). It's not an issue of veridical versus non-veridical seeings in the sense that Sellars is using that (namely, where a "seeing" is "S has come to believe that x is green").

The idea springs to mind that sensations of red triangles have exactly the virtues which ostensible seeings of red triangular physical surfaces lack. — Sellars, outlining the sense data theorist's course of thought

It's not clear to me how you're using "seeing" there so that it's different than "sensations of red triangles" by the way. Again, Sellars' distinction between "looks" and "seeings" seems to be that "looks" is another term for sense data (a la "x looks F to S") and that "seeings" are inferential statements of the sort "S has come to believe that x is F"). But you don't seem to be using "seeings" the same way as that above.

Of course, talking about sense data in that way, it's unclear why we'd be supposing that any(one is saying that any) sense data are or can be necessarily veridical. — Terrapin

Right, that's Sellars point! — csalisbury

Then why would we be talking about it as if anyone is saying that?

Can't an experience be foundational without being able to be known that they are in every (or even most) instances? But yeah, I think this is orthogonal.

That's not what I'm addressing here by this though: "Why couldn't someone who believes that sense data are necessarily veridical have the view that non-veridicality isn't even coherent, for example? In that case, it would be dubious to say that they've experienced something non-veridical."

What I'm saying is that it's a logical possibility that Joe, say, believes that sense data are necessarily veridical, where Joe is saying something about sense data correlating with existents that are not themselves sense data, and where Joe has a view that non-veridicality isn't even coherent. That's a logically possible stance for someone to have.

Sure, so long as he has a different explanation of what seems like non-veridical experience (e.g. perhaps he'll have an explanation like the one TGW mentioned earlier: unlicensed inferences/invalid expectations.) Unless you're asking to imagine someone who has literally never had the experience of being in error?

But wait though. Sellars says for example, "The first idea clearly arises in the attempt to explain the facts of sense perception in scientific style. How does it happen that people can have the experience which they describe by saying "It is as though I were seeing a red and triangular physical object" when either there is no physical object there at all, or, if there is, it is neither red nor triangular? The explanation, roughly, posits that in every case in which a person has an experience of this kind, whether veridical or not, he has what is called a 'sensation' or 'impression' 'of a red triangle.'"

The part I emphasized is a description of sense data. "Whether veridical or not," then, is about sense data in this passage (per the explanation of sense data theorists which he's going to be addressing). It's not an issue of veridical versus non-veridical seeings in the sense that Sellars is using that (namely, where a "seeing" is "S has come to believe that x is green").

But the part you emphasized isn't a description of sense data. It's saying (in the voice of the sese data theorist) that sense data is a necessary condition for both any experience of an object and any experience that seems as though its of an object. Note that 'whether veridical or not' refers not to 'a sensation or impression' but to ' an experience of this kind.' And 'experience of this kind' refers to those experiences where it's 'as though [one] were seeing a red and triangular object.'

The end of that paragraph of you quoted the beginning of makes all this very explicit:

The core idea is that the proximate cause of such a sensation is only for the most part brought about by the presence in the neighborhood of the perceiver of a red and triangular physical object; and that while a baby, say, can have the 'sensation of a red triangle' without either seeing or seeming to see that the facing side of a physical object is red and triangular, there usually looks, to adults, to be a physical object with a red and triangular facing surface, when they are caused to have a 'sensation of a red triangle'; while without such a sensation, no such experience can be had.

It's not clear to me how you're using "seeing" there so that it's different than "sensations of red triangles" by the way.

You mean how Sellars is using 'seeing' there? That's a quote from Sellars, not me.

Then why would we be talking about it as if anyone is saying that?

It's claimed by Sellars that sense data theorists do say that, or at least make implicit use of the idea.

Sure, so long as he has a different explanation of what seems like non-veridical experience (e.g. perhaps he'll have an explanation like the one TGW mentioned earlier: unlicensed inferences/invalid expectations.) Unless you're asking to imagine someone who has literally never had the experience of being in error? — csalisbury

The latter. If someone believes that the very idea of non-veridicality is incoherent, they're not going to have the experience of being in error.

And 'experience of this kind' refers to those experiences where it's 'as though [one] were seeing a red and triangular object.' — csalisbury

How is it as though one is seeing a red and triangular object to a sense data theorist if one is not having a sense or impression of a red and triangular object?

It's claimed by Sellars that sense data theorists do say that, — csalisbury

Okay, but I said that it's unclear why we'd be supposing that any(one is saying that any) sense data are or can be necessarily veridical. Hence that isn't Sellars point if he's making that dubious claim.

The latter. If someone believes that the very idea of non-veridicality is incoherent, they're not going to have the experience of being in error

right, but then the idea of veridicality is going to be incoherent as well - if you can't understand the one, you can't understand the other.

How is it as though one is seeing a red and triangular object to a sense data theorist if one is not having a sense or impression of a red and triangular object?

You wouldn't be able to, for the sense daa theorist. That's why the latter is claimed to be a necessary condition for the former.

Okay, but I said that it's unclear why we'd be supposing that any(one is saying that any) sense data are or can be necessarily veridical. Hence that isn't Sellars point if he's making that dubious claim.

I don't know if I understand. It isn't Sellars' claim. It's what he claims the archetypal sense data theorist claims (or at least implicitly believes)

Can't an experience be foundational without being able to be known that they are in every (or even most) instances?

Yes, I think so, but then (if you're of a certain bent) it becomes a question of whether its a sturdy foundation. I think ultimately it actually is a cartesian question of certainty, I think terrapin might be right on that score (he just seems to confuse Sellars' view with the view of (Sellars understanding of) the sense data theorist.)

'Science and Metaphysics' is a good starting point to examine Sellars' philosophy of perception. It would be helpful to understand 'Empiricism and the Philosophy of Mind'.

Neither sort of light is ontologically privileged. What would actually be the case with the object is that in light 1, it looks green, and in light 2, it looks blue. Both would be accurate. — Terrapin Station

I'd also go further and add that not only does the object look a particular colour in a particular light, but that that object IS that particular colour in that particular light (from a particular perspective, of course). The object's properties are being directly affected by the properties of the light source, which is affecting the properties of our perception of the object. So the object is "blue" in one kind of light, and "green" in another kind of light, and so on.

I'd also go further and add that not only does the object look a particular colour in a particular light, but that that object IS that particular colour in that particular light (from a particular perspective, of course). The object's properties are being directly affected by the properties of the light source, which is affecting the properties of our perception of the object. So the object is "blue" in one kind of light, and "green" in another kind of light, and so on. — numberjohnny5

I don't think this works, because the physics will not agree with that (it's the same wavelength in all cases, and nothing has changed on the object's surface), and you have optical illusions where we see color that isn't there at all.

It's clear that we're seeing the object as different colors in different lighting conditions, because that's how our color vision works, not because the object has different colorings.

If anyone wants to reject the above on idealistic grounds, you still have to account for optics and illusions. In idealist terminology, our experiences are in disagreement with one another as to whether the object's color changes.

right, but then the idea of veridicality is going to be incoherent as well - if you can't understand the one, you can't understand the other. — csalisbury

I don't at all buy that idea in general--that one can only understand (or think etc.) some x if one can understand (or think etc.) not-x or x's "opposite."

Someone could easily think that sense data necessarily get non sense data right a fortiori because it isn't even coherent to suppose that they could not get sense data right. For a hypothetical justification of this, imagine if someone were to think that sense data determines, in a causal way, what the non-sense data world is like, and that the non sense-data world couldn't even be otherwise. The idea of non-veridical sense data could thus be incoherent to them--it wouldn't even make any sense to them to try to imagine that the world could be otherwise, because it's so obvious to them that that's how the world works. Thus they take talk of non-veridicality to be completely vague nonsense that other people engage in.

You wouldn't be able to, for the sense daa theorist. — csalisbury

Right. Hence when we talk about veridical and non-veridical "seeing a red and triangular object" we're talking about veridical and non-veridical sense data when we're talking about sense data theorists.

It's what he claims the archetypal sense data theorist claims (or at least implicitly believes) — csalisbury

Right--that's Sellars' claim. But I don't know why we'd be claiming that any sense data theorist believes that, as there doesn't seem to be any reason to claim that. In other words, it's extremely dubious that any sense data theorist actually believes that.

Yeah, I agree with that.

I don't think this works, because the physics will not agree with that (it's the same wavelength in all cases, and nothing has changed on the object's surface), and you have optical illusions where we see color that isn't there at all. — Marchesk

It's not just the object's surface that's pertinent. It's the whole "system" in question--the object's surface, the light traveling from it, the way the light interacts with the atmosphere, the wavelengths at a particular point in space (the surface of your eye for example). Hence his "from a particular perspective."

It's important to remember that EVERYTHING we say is from a particular perspective, and there are no objectively privileged perspectives.

Right. Hence when we talk about veridical and non-veridical "seeing a red and triangular object" we're talking about veridical and non-veridical sense data when we're talking about sense data theorists.

Before going further, I want to back up to the beginning of this thread of argumentation:

It's extremely dubious that any sense data theorist would say both that (i) there are both veridical and non-veridical sense data, and at best we have methods of knowing that some sense data are more reliable than others, and (ii) they're forwarding sense-data theory in a bid for epistemic certainty — Terrapin

I want to make sure I understand what you were saying here. I took you to mean that that it doesn't make sense to turn to sense-data for epistemic certainty, if one believes that it is characteristic of all sense data that we can only know to a limited extent whether they are 'veridical.' To hold such a position would be to contradict oneself. Is that what you meant?

The key is the first phrase: "It's extremely dubious that any sense data theorist would say . . ."

I'm talking about what sense data theorists would say about their views. Comments and claims are being made about what their views are/what they would say. I'm skeptical of those comments and claims.

That's fine - I too could do with some citations or examples early on - but I think he provides ample historical evidence to support his claims (about the claims of others) as the essay progresses.

In any case, I just want to make sure I understand how you understand the claims Sellars imputes to the 'sense-data-theorist.' Was I reading you right?

I took you to mean that that it doesn't make sense to turn to sense-data for epistemic certainty, if one believes that it is characteristic of all sense data that we can only know to a limited extent whether they are 'veridical.' To hold such a position would be to contradict oneself. Is that what you meant? — csalisbury

I took you to mean that that it doesn't make sense to turn to sense-data for epistemic certainty, if one believes that it is characteristic of all sense data that we can only know to a limited extent whether they are 'veridical.' To hold such a position would be to contradict oneself. Is that what you meant? — csalisbury

That's not what I was saying, but sure, if one were making a claim about epistemic certainty yet at the same time saying that one can only know to a limited extent whether the method in question entails veridicality, then yes, I'd agree that that wouldn't make sense.

That's not what I was saying

Could you point to where I'm misreading you, or possibly re-phrase what you were saying? I'm just trying to pinpoint the exact source of our disagreement.