In a previous post, I asked whether it is possible to objectively compare the quality and validity of different pieces and forms of art. In the responses I got the overall response is that there is no accepted way, and it might be impossible all together. I still struggle with the idea, that even if we could never differentiate between Pink Floyd and Justin Bieber or Martin Scorsese and Michael Bay, surely there are extreme cases which can be dismissed as commercial or insincere art. For example in the case of film arts, surely advertising and most internet pornography don't qualify as legitimate artistic expression. But it seems that even that is not possible (see this reply to my pervious post).
But then I came across the statement "I know it when I see it", in particular the way it was used by US supreme court justice Potter Stewart:
The phrase was famously used in 1964 by United States Supreme Court Justice Potter Stewart to describe his threshold test for obscenity in Jacobellis v. Ohio.13 In explaining why the material at issue in the case was not obscene under the Roth test, and therefore was protected speech that could not be censored, Stewart wrote:
"I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description ["hard-core pornography"], and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that."
There is no reason to look, as we have done traditionally—and dogmatically—for one, essential core in which the meaning of a word is located and which is, therefore, common to all uses of that word. We should, instead, travel with the word's uses through “a complicated network of similarities overlapping and criss-crossing” (PI 66). Family resemblance also serves to exhibit the lack of boundaries and the distance from exactness that characterize different uses of the same concept.
Justice Stewart used this "I know it when I seen it approach" to differentiate between obscenity and acceptable porn. But it seems to me that we can use for at in general.