A poem should not mean
Assuming I understand it, I agree with it. In fact I extend it well beyond poetry. My primary concern is usually stories, and I would say the same thing, a story should not mean, but be.
This has had a tendency to get push back. "Haven't you heard about symbolism and allegory?" I have been asked. Yes, I have. But here's the thing: those are hard to do well.
Before I expand on that, let me say this: a poem will always mean. A story will always mean. People are meaning creating machines. We couldn't create something meaningless if we tried and even if we did the reader/hearer/viewer/player/experiencer would find their own meaning in it. But the poem "Ars Poetica" is not about poems but the art of poetry. It's addressed to the poets, and so I take the statement "A poem should", repeated six times in the full poem as a message to the poet about what their priorities should be.
I would expand that the the creators of all fiction, non-fiction as well but that should be obvious since to even be non-fiction it has to be about what actually happened, otherwise it's just fiction packaged as non-fiction.
So I take it to mean not that the result shouldn't have meaning, but the meaning shouldn't be the top priority, instead the being should be.
Which brings us back to symbolism and allegory.
In both the idea is that something stands in for something else. The stand-in is what's actually in the poem/work of fiction (and thus the being of the poem), the meaning is what it's standing in for. In a well crafted work with symbolism or allegory the stand in is chosen so well that, within the work itself, the stand-in and the thing it stands in for never conflict.
That is hard.
It is hard because the stand-in is not the thing it stands in for, that's what makes it symbolism or allegory, and so they will not be the same in all situations. Sometimes there will be a place where stand-in would do X and thing stood in for would do Y. They are different things and getting different things to act the same way isn't always easy.
To have well crafted symbolism/allegory you have to choose a stand-in that will act like the thing stood in for in every important situation that comes up in the whole of the work.
The same goes with deeper meaning that doesn't involve symbolism and allegory. Maybe you have a message you want to send, but to do it well you need to make sure that the stuff actually in the work, the work's being, doesn't conflict with that message. It can be hard to do.
And since it is hard to make the things line up, the result is that they often don't. Meaning goes one way, being goes the other. The creator has some options:
1) Give up in despair
2) Major rewrite so that when it reaches this point the meaning and the being don't conflict. You've got to change the being somehow, but in doing so you've got to look back at everything that came before to take into account how whatever change you made would have influenced that stuff and rewrite accordingly.
Say your allegory requires a character to make a certain decision, but what you've written before shows that that character isn't the sort of person who would make that decision. You'd have to change the character, which means changing how the character was portrayed before, every action, every interaction, has to be reconsidered, every result from either. The changes potentially cascade outward in ways that potentially change everything. It might be easier to to restart from scratch.
3) Keep what has come before unchanged, ignore the intended meaning, and follow from the story/poem/show/movie's being. Go with what's on the page, so to speak, and let it be what it will. The meaning will take care of itself, even if the result isn't the meaning you intended.
4) Keep what has come before unchanged, ignore what that tells you about where things are going, and tell the story that the meaning requires.
1) Doesn't result in a finished work, and need not be considered.
2) If done right, produces a finished product indistinguishable from something where meaning and being never conflicted in the first place.
Three and four are where I see the meaning being conflict. Three is what you do if you think things should be rather than mean, if you think what is on the page is more important than the intent behind it. The intended meaning may be mangled, but the story will be internally consistent. No one needs to act out of character, nothing needs to come out of left field, no established rules need to be broken, so on, so forth.
Four, in my opinion, does not work. Because it sacrifices what's already established in favor of what the creator wants to say and that always shows up. A character suddenly acts out of character, a situation is obviously contrived, a well established rule is broken, things make no sense in context. The difference between what was supposed to be symbolized and the thing used to symbolize it is such that what was supposed to be an ok relationship becomes an abusive one in the context of the work. Stuff like that.
But the result is more than just poor art.
The conflict between the meaning "This is just supposed to represent [whatever] so the fact it doesn't actually make sense when taken literally is ok," and the being, "Given the actual situation presented This Does Not Make Sense/Is Downright Evil Though You Call It Good," undermines the meaning. It makes you look at it and think, "Ok, so maybe it meant X, but given that they had to do [atrocious writing] to get there, why in the hell would I accept that their views on X have any value? They had to be dishonest with the reader/viewer to reach that point."
Choosing meaning over being undermines both. Choosing being over meaning risks producing a meaning never intended, but it produces better art and it means that whatever meaning is produced will be stronger for staying true to what has come before. A stronger being creates a stronger being.
Art will always mean and be but if forced to choose between the two as an artist, staying true to meaning, or staying true to being, then this is what you should keep in mind, "Art should not mean, but be."
[This could be considered the almost from scratch reincarnation of a comment at Ana Mardoll's.]
* Technically if you want to be extremely literal it's closer to "the poetic art" because the way Latin formed the name of a given art form was "ars" plus adjective, where the translation "of poetry" implies a genitive noun which "Poetica," is not. The important thing is it's about the art form, not the result. It's about making poems, not poems, not reading poems.