Truth is Relative

No, some truths are relative, others are absolute.An example of a relative truth is your coloured triangle. Colour is a private mental experience, and it makes a difference whether the experiencer is a human, a dog, or an ant. In the outside world colour does not exist, so anything you say about colour is at most a relative truth.An example of absolute truth is the fact that there are infinitely many rational numbers.

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"Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science." - Charles Darwin.

The wavelength of light is not the same as the experience of a colour. When I look at light with a certain wavelength, my experience of it differs from that of, say, a dog. It's true that we're both looking at the same wavelength, but our experience of it is not the same.Saying that light with a wavelength between 520 and 570 nm is green is the same as saying that boiling water is pain. Both are nonsense. It's better to say that boiling water (if touched) causes the sensation of pain, and that light with the wavelength mentioned above (if seen) causes the sensation of green.

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"Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science." - Charles Darwin.

By "outside world" I meant everything outside my (or your, or any other creature's) mental experience. See my reply to ikabod above. Can you say where in the outside world pain is? Even if numbers only "exist" in a sort of Platonic realm, then it is still an absolute truth that there "exist" infinitely many rational numbers. Edited by Parasomnium, : added "(or your, or any other creature's)"

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"Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science." - Charles Darwin.

I think a clarification is in order here. When I gave my example of an absolute truth, I was no longer referring to the "outside world" of my previous example of a relative truth. I also stated in a later post that it doesn't matter in what way rational numbers are deemed to exist, Platonic or otherwise. I said this because the absoluteness of the truth of my example, rather than about their actual existence, is more about the infinity of the set of rational numbers, in the following way: once the ancient Greeks proved that the set of rational numbers is infinitely large, they saw that this had always been true. And it has ever since been true, and it always will be.Sorry if I inadvertently sparked a debate about the reality of numbers, I never meant to. Actually, I would have been more interested in such a debate about my other example, the reality of the colour red.

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"Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science." - Charles Darwin.

OK, I'm game. In messages 30 and 36 you're effectively saying that the colour is the pigment. But how does that square with the fact that when I see a red rose in the dim light of a watery morning sun, its colour looks quite different than when I look at it in the bright light of noon? Clearly the pigment hasn't changed, but the colour - or at least my perception of it - has.That's my point really: colour is nothing but perception. "Outside", there are only molecules and light waves. Red is in my head. And only there.

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"Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science." - Charles Darwin.

Ben, I'd be happy to talk about things "mindspace", please go ahead.I realize that "red" is a kind of shorthand for light of certain wavelengths, but in essence light can be completely described in physical terms without referring to colour. There's energy, wavelengths, light speed, frequencies, particles even. Colour, as a concept, is not necessary to describe the physics of light. Colour only comes into play when we want to describe what it is like when we see light, and then we can't describe it. That's the meaning of the word 'colour' that I'm talking about.To me, the essential thing about red is what it is like to see a picture like the one below. I can, in principle, completely describe what happens physically when I look at the picture, from the reflection (or emission, in the case of a computer screen) of light from the picture and its refraction by my eye's lens, to the excitation of my retinal cells and the subsequent neural firings in my brain. Nowhere along this path do I need to invoke the concept of colour. Although such a concept might be handy in part of the description of what happens in the retinal cells, it is not strictly necessary, I can also speak about wavelengths to describe exactly what happens. And if I could have the experience of, say, an insect when seeing a rose, it might even be flatly wrong to describe the physical process that causes the experience in terms of specific colours.But when it comes to describing the experience itself, no words are sufficient and no physical concepts convey the meaning. The only way to tell you what it is like for me to see red is to have you look at the same thing and hope that your experience is similar to mine. Although I cannot express what it is like for me when I see the picture above, I have reason enough to assume that it is similar to what it is like for you, because biologically and physically you and I are very much the same, and it is therefore reasonable to assume that our experiences are very similar. But I can't be sure of course.However, even if - unprovably - your experience of the picture above would be very different from mine, I still think that whatever either of us would think is the essence of colour, is our pure perception of it, because everything else about the processes that cause us to see colour can be described in words and concepts without any reference to colour whatsoever.Edited by Parasomnium, : No reason given.Edited by Parasomnium, : No reason given.

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"Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science." - Charles Darwin.

A quite amusing example in this context is the pigment Brazilin, which has the chemical formula C₁₆H₁₄O₅. You can see its molecular structure in this picture: The funny thing about Brazilin is that it can have two different colours: in an alkaline solution it appears red; but in an acidic solution, it appears, wait for it, yellow. Now, if pigments have an intrinsic colour, as you seem to suggest, then in the case of Brazilin we're facing a dilemma as to which intrinsic colour to assign to it. Is it intrinsically red or yellow? I am not denying that something exists that causes colour experiences in us and in other animals. I just think that to say that something is red is to say nothing about the thing itself, but everything about what it is like to see it.

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"Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science." - Charles Darwin.

That's irrelevant. Even without human interference, Brazilin will find itself in an alkaline environment, or an acidic one, or a neutral one. Whatever the environment, the question remains what the intrinsic colour of Brazilin is. That is, if there is such a property as 'intrinsic colour'. It is my contention that there isn't. Again, I'm not saying that colour doesn't exist, all I'm saying is that colour is a perception, and as such doesn't exist outside the mind of those who perceive it. If redness was an objective property of things, should it not then be possible to tell a person who has never seen red what it's like to experience seeing red, without showing them? Sure, you can tell them that light of certain wavelengths hits their retina, and that neurons start to fire, and that the visual cortex is activated. But can you convey the redness of red? Can you make them see red just by telling them? You can't.Of course there is something out there that triggers perceptions in a perceiver, but since the same outside thing can trigger quite different perceptions in different animals, you cannot equate the outside thing with just one of those perceptions and ignore the rest. The only logical conclusion is that no one perception is equal to the outside thing. What you should have said, in my opinion, is that having a certain chemical composition seems to have a purpose in nature, because that chemical composition triggers certain responses that seem useful.

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"Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science." - Charles Darwin.

You're right in that the concept of colour is a convenient shorthand to talk about wavelengths of light. Such a convenient shorthand it is that even if you don't know you're actually talking about wavelengths, you can still have a meaningful conversation about it.But to me that's a trivial aspect of colour. What really interests me is the essence of colour: that which first comes to mind when someone mentions the word 'red'.

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"Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science." - Charles Darwin.

The first thing I get when I hear "red" is a vague version of the picture I posted upstream in this thread. That's what I'm talking about, that's what I mean by the "essence of colour".

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"Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science." - Charles Darwin.