I've been, as my readers my have observed, been mulling over whatever it is that photographers use as a philosophical basis for what they do. Whatever justification or goal they aim for.
Weston seems to have wanted to show the true essence of the thing. Adams wanted to reveal his true emotional reaction to the thing. Doc McCullin (currently on display at the Tate, raising the hackles of the photographic intelligentsia all across England) seems to have had something about showing the true human dignity of subjects in dire straits. Emerson wanted to reveal his true Impression of the scene.
There's usually something about Truth rattling around in there, because after all that's what photographs do best. You could take some other tack, but I haven't run across any such thing.
This probably isn't quite what separates the good from the bad, but boy it might be the factor that correlates least badly.
It does seem to align nicely with this distinction, which I like to carp on: the difference between perfectly good, pleasing, well-made pictures; and pictures with real weight.
Over on Leicaphilia, the intrepid writer shared some ideas on Joel Meyerowitz who strikes me very much as a philosophy-free fellow who just rambles around taking perfectly nice pictures that don't mean anything. I bought his Tuscany book at Goodwill for $3. It's very nice. Some day I am going to cut it to bits and make something better out of it. Michael Reichmann was another such, loads of perfectly nice pictures signifying nothing much. In 50 years, nobody will remember either of these photographers.
Now, to be fair, I also have one of these philosophy things, and nobody is going to remember me in 50 years either. It's not guarantee of success, but longevity and weight seem to, maybe, require it or at any rate bias heavily toward those who have one. Or a couple.
It's not a big thing. It doesn't have to be a PhD thesis. It doesn't have to be very precise, you don't even need to follow it all the time. But some kind of general slogan that drives your work seems to be a really good idea. For one thing, it makes the pictures better.
What the general shape of thing ought to be is this: you ought to be able to ask of any picture you take "does it do that thing?" and it should not be terribly specific, and certainly not photographically/technically specific. This lets you, obviously, make work that is bound together, that is all alike in some fairly vague and non-technical sense, in some sense therefore that might be a little more important than "has good shadow detail" or "is very sharp indeed."
Mike over on ToP has posed the question recently Has Photography Gotten Too Easy which is basically just pointing us to a sloppy and pseudo-erudite essay by Maria Popova which is essentially the standard whinge about instagram dressed up with citations and a bizarre reference to Herschel proposing a coating of sodium thiosulfate to Talbot as a method of fixing silver prints (which is insane, he cannot possibly have suggested a "coating.")
ETA: Maria Popova's blog appears to be, essentially, "My, what a lot of books Maria has read" adorned occasionally with "but she reads a leeetle too much Wikipedia" and mercifully short on whatever might pass for original thoughts from her.
Technically, yes, photography has become very easy. Duh. And now it is very easy to churn out more or less endless Good Pictures signifying nothing. Popova refers to "message" but doesn't mean it, she just means subjects.
The degree of difficulty required to bring to satisfying conclusion any kind of philosophical basis for taking pictures remains about the same, and now we know that all the technical horsing around wasn't very important after all. Which, you know, even Precisionists like Adams knew, and said, all along. Nobody was listening.
Nobody's listening now, either.