Right. To amplify that a bit:

To admit this is not to admit idealism though, because idealism claims that percepts are not merely mediated and added to, but entirely constituted by, ideas. — John

I don't think 'constituted by ideas' is quite it. Recall that Kant always claimed to be an empirical realist, i.e. if you asked him what something was constituted from, he would regard that as a question for physical chemistry. But he could still be idealist, insofar as claiming that our knowledge of physical chemistry, whilst sound in its domain of application, was still constituted in some basic way by our own cognitive apparatus, the categories of understanding, and so on. So I take his claims to be about the nature of knowledge and experience, not about the nature of things, as it is only by those means that we encounter things at all.

So I think to say that idealism says that everything is 'constituted' by ideas, is also a kind of naturalistic error, because you're still thinking about it in terms of what constitutes objects, rather than thinking about it in terms of 'what is the nature of knowledge'. When you see the visual ilusion I mentioned, or anything else, that 'seeing' is itself a perceptual operation; so you want to ask 'what is the object apart from the perception of it', but by asking that, you're trying to get outside the very act of knowing.

It's no secret that the mind can sort of 'fill in' details where they 'normally' would be to produce a kind of impression. But you're not actually seeing the edges of the triangle except where there is black and white contrast. — John

But where you see a white edge, there is only just unedged whiteness. So you are seeing a triangle when you really shouldn't - even if this is the kind of foundational trick upon which the whole business of "perceiving reality" depends.

Dreams and hallucinations sort of fill in for reality in a big way. But the point is it is all "fill in" down to the finest grain of perceptual processing. Your epistemology has to be able to deal with that frankly.

To admit this is not to admit idealism though, because idealism claims that percepts are not merely mediated and added to, but entirely constituted by, ideas. — John

Well in a way they are. Or I would say signs, as in Peircean sign relations.

I would say that "categories and kinds" are not merely projections of the mind, but reflect the reality of the things being seen as kinds and placed in categories. Otherwise it would all be merely arbitrary and could never become systematic.

It is only the naive realist who thinks that things are there in the incoherent sense of "having a look when they are not being looked at". Things are, however, visible or invisible even when they are not being seen. And things may be said to be this or that colour when not being seen, although of course they do not appear to be this or that colour when not being seen. In the same way something can be round when not being seen or felt, on account of the fact that when it is seen or felt it will reliably be seen and felt to be round.

I find Kant's independently real noumena are really unintelligible, the in itself can only ever be in itself for us, so I prefer to think of things as being just as we see them to be. The things themselves can only be what we think, or come to think about them. What else could they be? But from this it certainly does not follow that they are mental projections. They, just like we, are manifestations of the Real, and they are brought into being just as we are, by our ideas. However they are nonetheless material for all that and are not constituted by ideas, which seems a ridiculous notion. For me this is logical realism, pure and simple.

I would say that "categories and kinds" are not merely projections of the mind, but reflect the reality of the things being seen as kinds and placed in categories. Otherwise it would all be merely arbitrary and could never become systematic. — John

I didn't say that they're projections. I said they we project them onto the independently real things. They're perhaps "inherent" (to some extent) in things as perceived.

Things are, however, visible or invisible even when they are not being seen.

What does it mean to be visible or invisible even when not being seen? Do you just mean capable or incapable of being seen by the typical human?

And things may be said to be this or that colour when not being seen, although of course they do not appear to be this or that colour when not being seen. In the same way something can be round when not being seen or felt, on account of the fact that when it is seen or felt it will reliably be seen and felt to be round.

What does it mean to be red and round even when not being seen? Do you just mean that it will be seen as red and round by the typical human?

Yes, I agree that Kant was no idealist of the kind I am targeting. I am thinking more of Berkeleyan idealism. Phenomena are, I agree, entirely constituted by experience and thought, but they are materially, not ideally, constituted. We conceive things as being constructed from bits of matter, not from bits of thought; the idea really makes no sense at all.

so you want to ask 'what is the object apart from the perception of it', — Wayfarer

No, that is precisely what I think it makes no sense to ask, at least if you are asking it in terms of 'what is the object considered entirely outside of perception', Of course in the ordinary sense as with science it makes sense to ask the question, because there is much that may be learned about things by modeling them in terms of mathematics and physics, understanding them in terms of causality, and so on. These are the kinds of things which are never given directly to perception, only percepts are given directly to perception. But those things not given directly to perception may be given to thought; so it is thought that tells us what things are like apart form perception in this sense, but nothing can tell us what things are like entirely outside the whole context of perceptual experience, because that idea can really have absolutely no meaning for us.

What does it mean to be visible or invisible even when not being seen? Do you just mean capable or incapable of being seen by the typical human? — Michael

No, I mean, for example, say you are looking at a field and there is a rabbit perfectly visible in the field, and yet you do not see it.

No, I mean, for example, say you are looking at a field and there is a rabbit perfectly visible in the field, and yet you do not see it. — John

That doesn't explain what it means to be visible. I understand it as just meaning "capable of being seen".

What does it mean to be red and round even when not being seen? Do you just mean that it will be seen as red and round by the typical human? — Michael

Yes, something like that.

Interestingly, Kant mounted an argument against Berkeley in the second edition of CPR (annoyed that many of his critics accused him of the same doctrine). It's Kant's 'critique of material idealism' - rather a good summary on SEP.

I can't see why it doesn't. Don't you know what it means for something which you are not seeing in a field to be visible nonetheless. Perhaps in the next moment you spot it, and yet it hasn't moved.

The epistemological idealist and anti-realist will accept that account of being red even when not being seen. But that's not the naive realist view. The naive realist won't define "is red even when not seen" as "will be seen as red by the typical person" but will use the former to explain why the latter is true.

I can't see why it doesn't. Don't you know what it means for something which you are not seeing in a field to be visible nonetheless. Perhaps in the next moment you spot it, and yet it hasn't moved. — John

I understand "visible" to mean "capable of being seen", as I said. I don't know what you mean by it, and simply saying "it's visible but you can't see it" doesn't help me understand what you mean.

Thanks Wayfarer, I have read Kant's refutation of idealism in the past.

Yes 'visible' means "able to be seen".

Right. Well, given that you said "no" that definition here you'll understand my confusion.

I can't see where I said "no" to it. Perhaps you could quote the actual passage where I purportedly said it.

Me: "Do you just mean capable or incapable of being seen by the typical human?"
You: "No, I mean..."

But, aren't you just cavilling over language here? In any case, how sure are you that most or even all naive realists will respond this way? Have you polled all or even most of them? I can't see why they wouldn't agree with that. What else could 'being red' mean, than 'will ordinarily be seen as red"?

Oh, I see where the misunderstanding lies, I was proposing a broader definition, where for instance something might be visible or not visible to a hawk, or a fox or any animal that can see, and I did not want to define it in a way that restricts it to your anthropocentric "typical human".

What else could 'being red' mean, than 'will ordinarily be seen as red"? — John

Presumably that things have a red appearance even when not being seen. The traditional naive view is that things have a look even if they're not being looked at. They say that we see a thing as red "because it really is red" – where this is an actual explanation rather than just a tautology. They say that if one person sees a thing as red and most other people see that thing as orange then it's not just that the former has an atypical perception but that she fails to see what colour the thing "really" is. And, of course, it's nonsense, which is why naive realism is wrong.

In nay case, how sure are you that most or even all naive realists will respond this way? Have you polled all or even most of them? I can't see why they wouldn't agree with that.

It's how naive realism is ordinarily defined; as the view that things have the properties we perceive them to have even when they're not being perceived.

Doesn't that mean that everything except dark matter is visible?

Well, I don't agree with your characterization of naive realism, and I don't see how you could possibly know that is what most of them think. You must think they are all morons, I mean it just doesn't make sense to say that things have an appearance when they are not appearing. Being visible when not being seen is not the same idea; it makes perfect sense. Naive realist that have not thought through their 'position' might vaguely imagine a world of objects 'out there' appearing the same as they do when seen, but anyone of even just average intelligence I believe could see that this doesn't really make sense when you think about it.

You say it is how it is ordinarily defined, but I think you are leaving out the part that says it is how it is ordinarily defined by its detractors.

Everything with a reflective surface and some light shining on it I guess. But really it only makes sense to speak about anything being visible from some perspective or other. Because if something is behind a mountain it is invisible from this side and visible (perhaps) from the other side. Something microscopic is visible only through a microscope, and so on. Maybe quarks will never be visible.

I don't know who defined it that way, but it's how the view is defined on the Wikipedia and the Stanford Encyclopedia of Philosophy pages. And it certainly fits the "naive" label, as it's likely the view that children (or anyone who doesn't understand the science of perception) have.

Well, since probably most people are, at least prior to reflection, naive realists I don't see how it could possibly claim to be characteristic of the way they would all understand it. Probably just another example of stupid philosophers defining terms to suit their own nefarious purposes.

Again, you cannot know that beforehand, since you do not know which experiences are hallucinations or not beforehand.

You're right. Philosophical rejections of naive realism also had the unfortunate consequence of jamming epistemology for the last 350 years with pointlessly complicated or obscure attempts to overcome a problem which arises from a simple fallacy of ambiguity regarding objects of perception. As if the illusory white triangle would be seen in the same sense as the black marks from which it is derived.

Again, I'm not looking at my own experiences wondering which is illusory and which represents reality. That's your problem, not mine. The objects of my experiences are the real objects that I experience, not elements of my experiences.

Do you have any illusory experiences, or is it possible for you to?

Sure, the experience of that white triangle, for instance. But the triangle has no lines of its own, and it is only experienced, not seen. Instead I see the black marks by way of which I experience a white triangle. When I see the black marks I can shift my conscious attention away from them and instead experience something I don't see, a white triangle.