Red Mary
this may interest or amuse those who know Frank Jackson’s story about Mary and the black-and-white room
A conversation, Christmas Day (December 25), 1929
SCHLICK: You say that colours form a system. Does that mean something logical or something empirical? How would it be, for example, if a person was locked in a red room for his whole life and could not see any colour but red? Or if a person’s entire visual field
contained only a uniform red? Could he then say to himself, ‘I see only red ; but there must also be other colours’?
WITTGENSTEIN: If a person never leaves his room, they nevertheless know that there is space beyond it, i.e. that there is the possibility of being outside the room (even if its walls were made of adamant). This is therefore not a matter of experience. It is a priori part of the syntax of space.
Does it, then, make sense to ask, How many colours must a person have experienced, in order to come to know the system of colours? No! (By the way, to think of a colour does not mean to hallucinate it.) Here there are two possibilities:
a) Either his syntax is the same as ours: red, redder, bright red, yellowish red, etc. In this case he has our complete system of colours.
b) Or his syntax is nor the same. In that case he does not know a colour in our sense at all. For if a sign has the same meaning, it must also have the same syntax.[1]
[1] Addendum, Monday, 30 December 1929
I was wrong when I presented the matter in this way. It is not possible to say anything, either in the case where a man knows only one red or in the case where he knows several shades of red. I want to give a simple counter-example that is very old.
What about the number of strokes that I can see ? I could also draw the following inference . If I can see 1, 2, 3, 4, 5 strokes and seen strokes have the same syntax as counted ones, then I must be able to see any number of strokes. This, however, is not the case.