Let's agree that something is art if the art world views it as art. Many famous painters were refused exhibition for years, only to have their rejected works considered masterpieces at a later date. Others were considered great artists, only to be virtually forgotten. Operas go in and out of fashion. Same with literary works. Does this mean that the same works can be art at some points in time but not art at other points in time?

"Let's agree that something is art if the art world views it as art." I think that we shouldn't agree to this proposition, precisely because it does seem that it has the relativistic implications you describe. So I take your question to be, "Does the institutional theory of art, e.g. George Dickie's (the theory that something becomes art if and only if the 'artworld' gives it this status) have the implication that something can be a work of art at one time and then not be at another?" The answer the institutional theory gives is that it is the totality of all the little artworlds at particular times and places inclusion in which at any time makes something art. Does this answer work? Does it make indeterminate today whether this is a work of art, as whether it is seems to depend on the possible response of some future art scene. Some ugly Greek pot is displayed in a museum by lovers of Culture today, so it was art even if the people who saw it at the time it was made dismissed it as crassly commercial or just ugly.

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