It would be aggravating and tiresome for me to attempt to rehash the whole art definition debate that was the subject of much philosophical discussion in the last century. And frankly, I’m not even up on the literature, so for all I know someone has come up with the definitive, final answer to the problem. But that seems unlikely, if not impossible. Art, like money or religion, is a cultural institution created by and sustained by the collective behavior of the species. Its ontological status is worth considering, but only in that context.
To answer the question of the necessary and sufficient conditions for a given work to be included in that class of objects one is forced to arrive at an answer that can only be objectively true when constrained by some temporal condition. So the first necessary condition is that the object be located, temporally, within the period that human culture acquired the collective behaviors that became known as artistic, or could be so-called by an informed observer looking backward at this range of human activity. But have I avoided circularity with this criterion?
That gets to the crux of the problem of the art definition issue. Which comes first? The institution or the artwork?
And to make matters worse, creative activity was done for various reasons throughout history and in very different contexts. There don’t appear to be any universal rules that define the variety of institutions that sanctioned creative activity. Certainly over history, religious institutions dominated, but not exclusively.
I believe it to be the case then that the correct form of the question is not about artworks themselves, but rather about the state of a given cultural institution. This points to a completely different issue in philosophy that is an outgrowth of philosophy of language. A philosophical account of cultural or social institutions is worth reviewing in a future post.
To summarize, any particular object known as a “work of art” in the declarative sense is an object that is so designated by appeal to the current norms of the prevailing cultural institution that governs such collections of objects.* There is no privileged ontological status for works of art. They obtain meaning and significance only to the extent that they fit within the matrix of collective behaviors that constitute the institution. It is worth noting, however, that it is possible to include historical works by declaration using the current convention, even though there existed no contemporary comparable institution at the time of creation. This act of appropriation is perfectly appropriate given that the objects attain a different status in virtue of their continued existence. It goes without saying that the intentionality of the artist plays no role whatsoever in this account.
Update: I neglected to mention that in the next part of this discussion I will attempt to distinguish between aesthetic valuation and artistic valuation (finally!) and try to defend my thesis that aesthetic properties are not relevant to, and are indeed outside the scope of, artistic evaluation in general.
*I also corrected a redundant sentence in the final paragraph.