Commenter Nigli, who knows a thing or two about it, has corrected me on a few points regarding wine and the tasting of it. In hindsight, I see I said some pretty idiotic things. Thanks Nigli!
It's obvious to anyone who is thinking clearly, i.e. not me, that there are things you can legitimately taste in wine (coffee, etc). This wine is bitter. Even a clod like me has experienced this bottle of wine is more something-or-other than the last bottle we opened. Some of this is, perhaps, suggestion. I am not immune to the fact that one bottle says Chianti and the other Syrah, but still, there is obviously something there.
Equally obviously, some people taste in detail than others, and furthermore these things can be enhanced by training and practice. Nigli mentioned a number of chemicals which are important, and which it is literally his job to taste. I believe him!
Translating this to Art, in particular photography, there are obviously things any clod can see. This picture is darker than that one and the like. There are things that more perceptive people and people with different backgrounds will note that other people will not. Things like this picture resembles that picture Diane Arbus took for example.
Still, the power of suggestion is quite real. If you dye a white wine red, clods like me will start tasting "red-like" qualities, and sommeliers will get confused. There is no doubt in my mind that one can plant suggestions of flavors that are not objectively present even if that flavor is a tasteable quantity. Can you slide these games past a trained palate? I assume, without evidence, that it depends on the owner of the palate, but that the answer is "sometimes, but sometimes not."
So in terms of flavors, there's stuff that's real in the sense of being objectively present in the beverage in some measureable sense, and that slides over in to stuff that's not real in the same sense. Then there's perceptions of flavors, which are a lot more plastic, a lot more subject to manipulation and suggestion. Obviously if you're perceiving something that's not objectively present, that's manipulation and suggestion at work. I dare say, again without much evidence but with great confidence, that suggestion can manipulate a person's perception of the stuff that actually is objectively present as well.
Now that this has been all muddied up properly, let's get back to the point.
The point is that when you look at Art (or tasting coffee), you're deploying a mental model which is informed by many things. Some of those things are inherent in the Art (or beverage) and some of those things originate elsewhere (the artist's statement, your memories, the text on the bag/bottle). Sometimes these areas overlap. The coffee does have notes of chocolate, because it has high concentrations of this chemical or that, but also because the bag told you so.
Consider these two notions:
Many of Henri Cartier-Bresson's photographs encapsulate a "decisive moment" which means something or other.
"her [Diane Arbus's] true subject was no less than the unique interior lives of those she photographed" -- Szarkowski.
These are both received wisdom. I mean, my God, Szarkowski said the second one! In my opinion, the first one is objectively true, in some sense, and the second is simply idiotic. I do think there's something to Arbus, but Szarkowski mis-identified it. Which is telling. However, I am no less subject to all these factors than anyone else. My opinion is really just a mildly educated and thoughtful guess.
To put it differently, I think there are objective, albeit perceptual, qualities in photographs. I fervently hope that people, in general, in some kind of blinded study would see something extra, something special, in at least some of what we consider the good pictures, the good portfolios, the good work whatever it is. You might consider this obvious, of course there's such a thing as a good photograph, what kind of dunce would even ask the question? Consider, though, that Szarkowski sees one thing in Arbus, and I see quite another (and Germaine Greer agrees with me).
If I am wrong, if the only difference between this picture and that picture is what it's a picture of and how the viewer has been primed, then photography has a problem. It's still not as simple as well it's all just subjective innit, wot? because whatever we do experience it is shared. The problem is that in this case the experience isn't based on the pictures, but on the story surrounding the pictures, which begs the question of what the pictures are for. If so, then it truly is the case that anyone can be a photographer, because photography is, then, truly about the stories we weave around the pictures.
My belief is that the story we weave is hugely important, but it's not the only thing that's important. There's something in the pictures too.