The problem is that you are mixing the use of “bitter” as a noun and as an adjective. So there are two meanings, bitterness, and something bitter. You need to correct for that. It is obviously true that the bark is not bitterness, which is the relevant conclusion.
The original context of this discussion is whether these things are meaningful. It should be pretty obvious that the whole discussion presupposes that they are, including your own remarks. So since this is obvious, there is no need for further discussion of whether they are true or false in particular.
In the proposition “purple is [not] bitter” it seems clear to me that “bitter” is being used adjectivally. Imagine someone with a variety of synaesthesia that makes them perceive bitterness whenever faced with something purple; then I would say that for them purple is bitter. (In much the same sense as we might say that quinine is bitter.) For most people, colour perception and taste perception are not linked in any such way and therefore purple is not bitter.
This seems reasonable to me. In any case the argument wasn’t really about whether purple is bitter, but whether the sentence “purple is bitter” has any meaning at all. In fact is obviously has at least one meaning (which you mention here) and potentially several.
The problem is that you are mixing the use of “bitter” as a noun and as an adjective. So there are two meanings, bitterness, and something bitter. You need to correct for that. It is obviously true that the bark is not bitterness, which is the relevant conclusion.
Huh? “Bitter” is an adjective—as you youself say, the noun is “bitterness”.
In both phrases—purple is (not) bitter and this bark is not bitter—it’s an adjective.
By the way, consider another phrase: Red is hot.
Is it true or false?
The original context of this discussion is whether these things are meaningful. It should be pretty obvious that the whole discussion presupposes that they are, including your own remarks. So since this is obvious, there is no need for further discussion of whether they are true or false in particular.
In the proposition “purple is [not] bitter” it seems clear to me that “bitter” is being used adjectivally. Imagine someone with a variety of synaesthesia that makes them perceive bitterness whenever faced with something purple; then I would say that for them purple is bitter. (In much the same sense as we might say that quinine is bitter.) For most people, colour perception and taste perception are not linked in any such way and therefore purple is not bitter.
This seems reasonable to me. In any case the argument wasn’t really about whether purple is bitter, but whether the sentence “purple is bitter” has any meaning at all. In fact is obviously has at least one meaning (which you mention here) and potentially several.