This roughly is the picture standing behind our idea that B must have “understood” the word “darker” differently from the normal person. On the other hand let us put side by side with this picture the fact that there is in our case no evidence for ◇◇◇“another sense”. ‒ ‒ And in fact the use of the word “must” when we say, “B must have understood the word differently”, already shews us that this sentence (really) expresses our determination to look at the phenomena we have observed after the picture outlined in this sentence.