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Is there any proof to Sir Isaac Newton's claim that color exists only in the mind? That there is nothing intrinsically blue about light with a short wavelength. To us it would look the same whether the cones in our retina detect color or whether they detect wavelength which our brains convert into color. Is there any definitive scientific evidence to prove or disprove his claim?

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    Do you have an extract to support your view of what Newton said? – Mozibur Ullah Feb 22 '16 at 11:36
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    is the blue color of the sky that you see in a dream different than the blue color of the sky that you see in waking life? if so then how? if not then how does that fit with the blue of the sky being an intrinsic property of light? – nir Feb 22 '16 at 12:36
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    Optiks 1704. The rays to speak properly are not coloured. Sir Isaac Newton. – Zane Scheepers Feb 22 '16 at 13:38
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    Consider abnormal colour vision and tetrachromatism: colour is subjective. – pjc50 Feb 22 '16 at 14:38
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    @DevSolar great answer. A trains whisle sounds higher pitched when its travelling towards us and lower as it moves away. Yet the whistle itself is making a constant sound. A similar red/blue shift occurs when objects are moving towards or away from us at near light speeds. This would indeed seem to support the idea that color is not intrinsic to light but rather a perception based on wavelength. – Zane Scheepers Feb 22 '16 at 21:55
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The human colour vision is bound to the cones. We have three types of cones with maximum of absorption in the wavelength domain respectively

  • violet
  • green
  • yellow.

The subjective impression of colour results from the neuronal processing by these types of cones by additive mixture of colours. The theory of Young, Helmholz and Maxwell from the 19th century explains this mechanism in our brain.

It is not the single wavelength which creates the colour impression. We do not have a continous range of receptors, each receptor restricted to one small range of wavelengths disjoint from the range of the next receptor.

Light is an electromagnetic wave like radiowaves. The only difference is their wavelength. We cannot detect any difference between radio waves in addition to their physical properties like wavelength, polarisation or intensity. Hence there is no evidence for colour as an intrinsic physical property.

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    According to sources I've looked at, the cones have a maximum absorption corresponding to red, green and blue (LMS respectively). – Bumble Feb 22 '16 at 13:56
  • @Bumble The maximum of absorption is violet (420 nm), green (535 nm) and yellow (565 nm) See: Schmidt, Robert; Schaible, Hans-Georg: Neuro- und Sinnesphysiologie. 2006 The authors explicitly emphasize that the long wavelength is not red. – Jo Wehler Feb 22 '16 at 14:38
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    Some humans also posses Tetrachromacy which gives them an extra green receptor (usually) that allows them to see green in a completely different way than other people. en.wikipedia.org/wiki/Tetrachromacy – Bradley Uffner Feb 22 '16 at 17:45
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    @JoWehler it should be noted, however, that different cultures (esp. different languages) do not necessarily agree on which color names correspond to which wavelengths. In particular, there is considerable difference between what Europeans call red, orange and yellow and what North Americans call them and where they draw the line between them (also blue and violet/purple). – RBarryYoung Feb 22 '16 at 19:09
  • And in many cultures green and blue were not distinguished. Colour words developed sophistication with developments in pottery glazes and dyes. In low light when only rods are activated, humans see in black and white. – CriglCragl May 14 '18 at 21:31
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Magenta

One of the simplest proofs: Perceivable colors cannot be the same as specific wavelengths because there is a range of colors which do not correspond to a specific wavelength. These colors are called magenta, pink, fuchsia, and the like. They are all colors which are placed on the so called line of purples (the straight line on the CIE chromaticity diagram).

CIE chromaticity diagram

Physical explanation

There are three types of cone cells (called S, M, and L) responsible for color vision in the human eye. Each type is sensitive to a range of wavelengths. If both the S and the L cones are stimulated, but not the M cones, the impression of the color magenta emerges. Because the main responsitivity ranges of the S and L cones do not overlap, one needs light of at least two wavelengths (a short "violet"/"blue" and long "red" wavelength) in order to stimulate both the S and the L cones, which in turn somehow trigger the phenomenal impression of the color magenta.

  • interesting answer... maybe you could add something about light waves not being composed of more than one wavelength. would that mean that objects (as well as light) do not have colours? – another_name Jul 4 at 17:57
  • @another_name A beam of light can indeed be composed of light of different wavelengths. In this sense we could indeed speak of magenta colored light if something reflects both short (violet/blue) and long (red) wavelengths. Equally, if we have light of some color, and it is reflected off an object, we can say the object has that color. I must admit that this somewhat runs against my original answer. – Max Jul 5 at 19:01
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The word color has 3 different definitions, depending on context. When speaking about the color of an object, we're referring to a property of the object. Which wavelengths of light it absorbs or reflects. When we speak about the color of light, we're referring to it's wavelength or the combination of wavelengths from which it is comprised. When it comes to visual perception, we're referring to hue. So a red balloon (property) under blue light (wavelength) appears black (hue).

Light has no hue, but it does have different wavelengths, which result in the perception of corresponding hues.

  • good answer and to the point, thanks – another_name Jul 4 at 18:09
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The "correct" interpretation of Newton's ideas and researches on light is a complex issue and Newton's theory for sure evolved during time.

But, having said this, here is an extract from :

So the true cause of [the phenomena experimented by Newton] found to be just this:

light consists of rays that are differently refractable.

[...]

I shall now tell you about another, more notable, unalikeness in light-rays, which is the source of differences of colour. I shall set out the doctrine first, and then describe one or two of the supporting experiments.

THE THEORY

You will find the doctrine comprehended and illustrated in the following propositions.

(1) Just as the rays of light differ in degrees of refractability, so they also differ in what colours they are disposed to exhibit. Colours are not what they are generally believed to be, namely states that light gets into because of how it has been refracted or reflected by natural bodies. Rather, colours are basic properties of light, properties that come into existence when light does, and these properties are different in different rays. Some rays are disposed to exhibit a red colour and no other; some a yellow colour and no other, some a green colour and no other, and so on through the rest. [...]

(2) A given colour always has the same degree of refractability, and a given degree of refractability always goes with the same colour. [...]

(3) The kind of colour and degree of refractability that any particular sort of ray has can’t be changed by refraction, or by reflection from natural bodies, or by any other cause that I have so far found.


See also Newton's theory of colour.

Newton's theory is that colours are not properties of things; they are the way we "perceive" wave-lenght, which is an "intrinsic" property of light:

the colours of all natural bodies have no other origin than this, that they are variously qualified to reflect one sort of light in greater plenty than another. And this I have experimented in a dark room by illuminating those bodies with uncompounded light of diverse colours. For by that means any body may be made to appear of any colour. They have there no appropriate colour, but ever appear of the colour of the light cast upon them [...].

  • The homogeneal light and rays which appear red, or rather make Objects appear so, I call rubrifick or red-making; those which make Objects appear yellow, green, blue, and violet, I call yellow-making, green-making, blue-making, violet-making, and so of the rest. And if at any time I speak of light and rays as coloured or endued with Colours, I would be understood to speak not philosophically and properly, but grossly, and accordingly to such conceptions as vulgar People in seeing all these Experiments would be apt to frame. For the rays to speak properly are not coloured. – Zane Scheepers Feb 25 '16 at 19:21
  • Not only does the scientific mainstream tradition conflict with the common-sense understanding of color in this way, but as well, the scientific tradition contains a very counter-intuitive conception of color. There is, to illustrate, the celebrated remark by David Hume: Sounds, colors, heat and cold, according to modern philosophy are not qualities in objects, but perceptions in the mind. (Hume 1738/1911, Bk III, part I, Sect. 1, p. 177; Bk I, IV, IV, p. 216) – Zane Scheepers Feb 25 '16 at 19:23
  • and plato.stanford.edu/entries/color It seems Newton, Hume,Galileo, Boyle, Descartes, Newton, Young, Maxwell and Helmholtz. Maxwell as well as the Stanford Encyclopedia of Philosophy disagree with you. – Zane Scheepers Feb 25 '16 at 19:26
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Is there any proof of Newtons claim that colours appear in the mind? That there is nothing intrinsically blue about the light with a short wavelength.

Newton may, surprisingly enough, demur; in part Book 2 of his opticks, he wrote:

Proposition 4: the transparent parts of bodies, according to their several sizes, reflect rays of one colour, and transmit those of another, on the same grounds that thin plates or bubbles do reflect or transmit those rays. And this I take to be the ground of their colours.

Newton appears to take rays to be coloured.

In a later chapter, he does claim though that vision is:

Qu.23: is not vision performed by the excitation of this medium, excited at the bottom of the eye by the Rays of Light, and propagated through the pellucid, uniform cappilimenta of the Optick Nerves into the Place of Sensation?

There's no mention of Mind, though; perhaps you've confused Newton with Hume, or perhaps Saussure; or both.

  • Place of perception! Is that not the mind? To be more specific, in sight it occurs within the occipital lobes. – Zane Scheepers Feb 22 '16 at 13:13
  • @Zane cheepers: the point is he doesn't bring mind into it; if you compare him to Hume, you'll see the difference... – Mozibur Ullah Feb 22 '16 at 14:35
  • I'm critiquing your argument from authority - what you say - that Newton said, in both your question and comments. – Mozibur Ullah Feb 22 '16 at 14:53
  • Stop wasting time arguing semantics. He says sensorium and I call it the mind. The point is that color is not a property of light or an object. Color is a sensation which we percieve internally and does not exist "out there". – Zane Scheepers Feb 22 '16 at 15:06
  • @zane Cheepers: you're wasting my time, my friend; Newton would call your finger, where you touch a coin to pick it up, a place of sensation; philosophy is about semantics... – Mozibur Ullah Feb 22 '16 at 15:11
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To follow up on the very good answer already offered by Max, we can observe that all the things in our natural environment that would have mattered to our survival as a species don't come in pure wavelengths. From this, we have to assume that our vision system has evolved and has been selected for by evolution not to be able to "measure" each of the possible pure wavelength but to be able to identify any particular mix of them.

It is therefore clear that having only three different types of cone cells in our eyes, each working on a specific range of wavelengths, is a very economical, and probably optimal, organisation if you keep in mind the cost for our metabolism of producing and maintaining the neurobiological "infrastruture" of our vision system. With such a low-cost "design", with only three types of cells, our vision system can identify a very large range of all the mixtures of wavelengths that occur in our environment.

You could still salvage your suggestion by insisting that colours really exist outside our minds or brains as mixtures of pure wavelengths rather than as pure wavelengths, but that possibility is really far too implausible to take seriously.

There is another reason. Light has one objective property which is its wavelength. It is an objective property because we can make experimental setups, for example the "double-slit interference", that produce observations that are best explained by assuming that light has a wavelength. If light had another, different, property, colour, we would expect to be able to observe some objective consequences. Yet, assuming wavelengths is all we need to comprehensively explain the objective behaviour of light. Colour doesn't explain anything that wouldn't be explained, and more gracefully, by wavelength.

The only thing we cannot fully explain with wavelengths is our subjective experience of colours. Indeed, we only experience colours as a subjective quality, something that as far as we know only occurs within the confine of our mind, whereas wavelengths explain elegantly everything that happens objectively outside our minds.

So, no proof definitive, but we won't have any such anyway for anything objective. Rather, we use common sense to opt for the more sensible option. Scientists say wavelengths and I agree with them. Still, you're the only one who can decide which option seems more sensible to you.

EDIT No. 2 : We can also all observe on ourselves that we can reliably make ourselves see colours in complete darkness, and in different circumstances.

First method: put yourself inside a completely dark room; check that you cannot see anything with your eyes wide open; close your eyes and press gently with you palms on your eyes for about 30 seconds. You may be able to see possibly very bright coloured spots forming around the centre of your visual field (and corresponding to the fovea). They will disappear after a minute or two.

Second method. Stay for five minutes in a completely dark room, eyes open; then, with your eyes still wide open, flash (i.e. very briefly) a bright light, for example using a spotlight, onto the part of the room you are facing. Once the light is shut off, you should be able to see the strikingly distinct remanent image of the room, and this even though you will be back in complete darkness. The effect last for a minute or two. This is the same effect as the blinding persistence of the image of the sun when you happen to look directly at it even briefly, something to be avoided of course.

So, colours and no light; ergo, colours are not intrinsic to light.

EDIT No. 1: Light has several other objective properties, such as intensity, speed and direction. All these other properties can be evidenced by well-known experimental setups.

Intensity is measured as a "macroscopic" property of light. It is the power transferred per unit area when light falls on a material. It depends on both the energy of each of the individual particles of light involved, the photons, and the quantity of these photons per unit area and per unit of time.

Intensity is the main objective factor affecting the subjective sensation we have of the brightness of light, whereas our subjective sensation of colour is mainly affected by the mix of wavelengths received by cone cells.

Light has also objective wave-like properties and particle-like properties, which can both be evidenced by experimental setups.

Intensity as a property of light is a function of the other properties of light that are its particle-like property, the energy of its particles, and its speed.

The direction of light is one of the objective factors affecting our subjective sensation of brightness.

Please note that all the elements used in this explanation are very basic and can be found in all science textbooks and from well-known and publicly available websites such as Wikipedia.

  • Actually, light has a second property which affects color perception. That's intensity, which affects brightness. – Zane Scheepers May 14 '18 at 21:24
  • Do you have references that would allow the reader to get more information? – Frank Hubeny May 14 '18 at 22:07
  • @ZaneScheepers Sure, which is why I said "our subjective sensation of colour is mainly affected by the mix of wavelengths received by cone cells". – Speakpigeon Jul 4 at 17:14
  • @FrankHubeny Sorry, no. This is from memory or personal experience. However, as I said at the end, "all the elements used in this explanation are very basic and can be found in all science textbooks and from well-known and publicly available websites such as Wikipedia". And also by conducting your own experiment (carefully). – Speakpigeon Jul 4 at 17:17
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If colour was intrinsic to light, then colour blindness should not exist, but it does therefore colour is not intrinsic to light. Red-green colour blind people detect light, but because of defects in their eyes cannot differentiate between the two colours i.e different wavelengths of light semingly have the same wavelength.

  • You have obviously never heard of representationalism – Zane Scheepers Aug 6 '18 at 21:22
  • Sorry! Not meant for you. – Zane Scheepers Aug 6 '18 at 21:22
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Color may be only in the mind, but remember that we associate colors with everything around us, and that is what gives them meaning. For example, the sky appears blue, the trees green and the sun yellow-orange. The universe is made up of colors or in other words differences which emerge from the oneness (of love) To truly understand why colors are so magnificent, you need to back to the creation and stare in wonderment of who we are. You might be interested to know that some species can differentiate more color than humans, as they have more than three types of receptors. Look up mantis shrimp for more information.

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