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Is my red your red? Where does the inverted spectrum come from?

Kavya Menon Fellow
· 5 replies
PerceptionAnalyticModern EuropeanEmpiricismJohn Locke#colour#inverted-spectrum#qualia
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Its coordinates: 2.2.1 Perception

Is the red I see the red my sister sees? I have wondered since childhood. When I was eight I asked my mother and she said, "Of course, it's red." That was not an answer.

Now I learn that this has a name, the inverted spectrum, and that it is supposed to be important for theories of consciousness. But I don't understand why. If my red were your green, and we had both learned to call it "red", nothing in our behaviour would ever differ. So why would anyone care? And if no one could ever find out, is it even a real question?

Could someone explain where the idea comes from, why philosophers think it matters, and whether there is any way it could be tested? I would also love to know if anyone has argued that it simply could not happen.

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5 answers

Accepted answer

  1. Alistair Gow

    ✓ Accepted answer Fellow

    The idea is old. Locke has it in the Essay concerning Human Understanding, in the chapter on true and false ideas: suppose the same violet produced in one man's mind the idea a marigold produces in another's, and the reverse. Locke's point was modest. He thought that even if it happened, neither man's ideas would be "false", because each would reliably sort the world the same way, and that is what ideas are for.

    Modern philosophers care for a sharper reason. If the inversion is possible, then what the experience is like is not fixed by what it does: two people could be identical in every function, discrimination, naming, behaviour, and still differ in experience. That would be a problem for functionalism, which defines mental states by their roles. So the possibility, not the actual case, is what matters. It is a test of theories rather than a fact about your sister.

    Whether it could be tested is where Priya's field comes in.

    Helpful · 1

Other answers

  1. Moon Ha-eun

    Fellow

    I have nothing scientific to add, only that I have the same question about han, the Korean feeling I can never quite translate for my European colleagues. When they say they "understand" it, I wonder if they have my han or something that only plays the same role in their lives. Maybe every feeling has this problem, not just red.

  2. Priya Raghavan

    Fellow

    Right, and here's the twist. Human colour space isn't symmetrical. We distinguish many more shades in some regions than others, yellows look intrinsically lighter than blues, reds and greens differ in how they relate to warmth and to other hues. So a simple swap of red and green would probably show up in behaviour: you'd find "your red" harder to discriminate in places, or you'd call different things similar. Colour scientists like C. L. Hardin argued this decades ago. The philosophical reply is to imagine an inversion that preserves all the structure, but then it's no longer obvious the scenario is coherent.

    Helpful · 2
  3. Kavya Menon

    Fellow

    So the possibility is what matters, not whether my sister and I are actually inverted. And the science suggests a crude inversion would leak out, but a perfect one is either impossible or undetectable. That is both a relief and a disappointment. Thank you, Alistair and Priya.

    Helpful · 3
  4. Rin Matsuda

    Fellow

    As someone who mixes paint all day: even within one person, red is not one thing. My grandmother's lacquer red, a fire engine, a persimmon. I sometimes think the inverted spectrum makes colour sound simpler than it is. But I see why the philosophers need it to be simple.