Originally posted by knightmeister
An outstanding example of a complete context error.
Do you mean "category mistake"? It isn't, anyway.
Look, it may well be that there is some "association" between the colour blue and certain wavelengths (in fact I'm sure there is). But in almost all contexts, when we use the word "blue", we are
not talking about wavelengths. Imagine you work in a factory and your sole job is to sort pieces of cloth into two piles - red and blue. Firstly, you wouldn't use a "wavelength" machine to do this in preference to the evidence of your own eyes. Secondly, we can imagine a case where you did use such a machine, but for some reason it started to give out typical "blue" wavelength readings when probing red cloths, and typical "red" wavelength readings when probing blue cloths. In fact we can imagine
every wavelength-measuring instrument producing similar readings. In such a case, we would
abandon the machines. We would not start calling blue "red", and vice versa. In fact for the thought-experiment to even make
sense requires that by "blue" and "red" we do not mean particular wavelengths, etc. Does that mean "blue" and "red" refer to some private mental impression? Absolutely not. They are properties of objects in the world. As Wittgenstein said, when someone remarks on the blueness of a sky, they are inclined to point at the sky; not at their head.
Look, your basic problems are twofold: you seem to think the only things that can be said to exist in the world itself are those that can be weighed and measured in a certain "scientific" way; and even worse, you can't even accept that the measure of how tall or heavy something is - expressed in our measuring concepts like miles and kilometres -
is a property of that thing. The first assumption is manifestly false; if you don't like the example of a mile, then how about a smile? Smiles exist, and are not conceptually identical with mouths. They cannot be reduced to mouths without losing certain distinctive, vital properties. The second assumption is so counter-intuitive it barely warrants a response. And I'm tired.