Let's try a summary and then give it a rest?
As I understand it Ms. Kamhi's position is that abstract art cannot be meaningful because all meaning in art is derived by its reference to something external to it-a picture functions as a conceptual symbol like a word. She feels that abstract art does not refer to anything in the external world - therefore it has no meaning. I prefer to define meaning in art as felt experience as well as conceptual reference and I also deny that abstract art cannot refer to anything external. Other than being in itself a physical event that can occasion a response(like a tree, it is an object) any painting cannot fail to reference something else as well-even an all-white painting refers to the physical property of "whiteness". We wouldn't say that Newton's third law is meaningless because it doesn't refer to a particuliar baseball-why should we reject a painting because it refers to a general characteristic (or organization of general characteristics) rather than a specific case?
My position actually includes that of Ms. Kamhi, but as part of a larger whole not exclusive as an end in itself. Closely examined, it can be seen that I am arguing from an inclusive individualist position that is not hostile to the vital root of her world-view.
A "collectivist" opinion would say that only what all(or most) people believe to be true is true. An "individualist" opinion would say that whatever each individual believes to be true is true. Absolutist individualism could not accept any collective opinion as true in any case. Any individualist cannot accept the opinion of one other (or many others) as true if it contradicts what he knows/feels as true. This need not be an absolutist position because an individualist can accept that collective opinion,physically demonstrated, is true and, even in some cases, in accord with his own if not demonstrable. An individualist will also acknowledge that he (and all other individuals) can perceive and experience a truth, or a level of truth, that is certain for himself but not the same for others.
Ms. Kamhi, by insisting that what is true for her and others must also be true for me, is arguing for a collectivist position. I am arguing for an individualist position. It would never occur to me to think I could see into another's mind and call delusional what they think and feel. Nor would I subject its veracity to a test by collective opinion, no matter how "expert" or popular and pervasive. I only ask that my mind be granted the same courtesy.
I applaud Ms. Ford's letter and its warmth of committment which addresses, primarily, the issue of quality in art. I would also like to reiterate one of the original subjects of this debate-a definition of art as a category-specifically a category of human product and effort. I think it's important to remember that a category does not necessarily confer value in itself. A hammer doesn't have value because it fits the category "tool" and the category "tool" doesn't automatically confer more value than something that fits category "cat".
A thing need not have(or lack) value to us simply because it is "art". For those who really do want a scientific definition of art as a category I can't improve on that of the anthropologist Kathryn Coe; "Color and or form used by humans in order to modify an object, body, or message solely to attract attention to that object, body, or message. The proximate or immediate effect of art is to [deliberately] make objects more noticeable" (1992. Art: The replicable unit -- An inquiry into the possible origin of art as a social behavior. J. Social and Evolutionary Systems 15(2):217-234.) Note by Neil Greenberg: "Coe's definition requires intentionality. Speaking of the appearance of an Acheulean handaxe of Homo erectus (200,000 BP), if the craftsman did not go beyond pure functionality it was not art: "Aesthetic 'attractiveness' thus may be an unintentional consequence of use, and hence not art" (p. 223).
This is, of course, not the full spectrum of what art is and can be-it is only a base, a category,-no mere definition should be more.