Is "blue" really there in the world, whether it looks blue to you or not? Or is something only "blue" if it looks blue to you?
Both Philip and Phoebe are partly right and partly wrong in what they say. To sort things out for them we will have to look at three different issues.
Phoebe is correct that "blue" is an experience, not something really there outside our heads in the world.
But Philip is also partly
correct because some objects (those that give out light of the wavelength he mentioned) usually give an experience named "blue"
by most people.
We learn what "blue" means as a young child by other people pointing at various objects and saying 'blue!'
some trial and error, we get the idea that they are talking about this strange experience of colour in objects, rather than something
else (like "good to eat", or "hot" and so on). So we try pointing at things ourselves, and saying 'blue!' until the reaction of other
people tells us we are getting it right. This means that Philip is partly correct: you can be right or wrong about colour, it is not
just a matter of opinion.
But there's a problem here. Take two young children learning their colours together.
They both learn to say 'blue' when an adult
points at certain objects. But we don't know whether they are having the same experience of the colour. One child may be having
exactly the same experience as the other does when looking at green objects. It's just that he or she is learning to name that
experience "blue". So Phoebe is also partly right: "blue" may differ from one person to the next.
If you think about it, the answer to this question is clearly no. You cannot climb inside
someone else's head and see what they
see. From what they say about their experience you might guess you are both experiencing the same thing, but you cannot be sure.
As we've seen above, if someone says 'What a lovely orange sunset!' you can't be sure they are experiencing its colour the same as
So "colour" is a complex matter. Maybe Philip and Phoebe weren't being so silly in disagreeing about it after all!
Synaesthesia is an illness where the sufferer experiences things in a highly unusual fashion.
In some cases, hearing sounds
triggers the experience of colours inside the brain. You can find out about this fascinating condition by clicking here.