Weird, I wonder where I got that notion from?

> so there has to be some numeric metric one could use to separate the very best from the "just good". What is it? (Perhaps it's not an easily calculable number, but it still must exist; if it didn't, then the whole field of art and literature criticism would be nonsense.)

That's where I got confused. I thought you were being sarcastic when you said that that art can be converted to a number.

I think it's possible (or very likely) that no such metric exists, and that if it did, it would be of little value. For instance, do you rank art based on aesthetic value, or the visceral effect it has had on viewers (mean or max?), or societal impact? Perhaps all the factors, but how do you weight them? Is there an objective measure of aesthetic value? It's more likely that different individuals/groups/cultures have different aesthetic tastes that vary over time, so perhaps you average over these variables? By averaging over these variables, will the "best art" be the perfectly pleasant art you might find hanging in a hotel lobby? Or will it be bolder art that a subset of people will revile? Who gets to decide?

There's always a chance that art can be converted into a meaningful and objective number. But if this metric does not exist, then by your logic, "art and literature criticism would be nonsense."

In my personal opinion, art is by its nature subjective. Aesthetic value is rather arbitrary. Art criticism is probably mostly a sham. But without them, how would rich people know which paintings to buy? Most people like being told what to like, what to wear, and when to laugh, and so they provide a useful service.