Robert Hughes, Time magazine's art critic and author of many books of his own including Shock of the New and American Visions, both of which I HIGHLY recommend for art, had an interesting idea about flatness. He noted the influence of the Eiffel Tower, built 1889. The view from the top of the Eiffel Tower was revolutionary and showed a very flattened world, one with a view completely different from traditional Renaissance perspective.
Yeah, I agree with your provocative comment about the spirituality of modern art, though I'm pretty sure I'd like to exclude plenty of it from that characterization.
I, too, would drop many modern artists from my spiritual characterization, but the good ones are spiritual. Actually, I think many "modern" artists (from, say, 1900-1960) were often spiritual. It's the postmodern and "contemporary" artists after 1960 who are purposely not spiritual, and often, I think, their work is empty and souless. I'll have more to say about these guys later on.
I read Robert Henri's "The Art Spirit" in the last year, liked it quite a bit.
I haven't been that fond of his portraits, I guess I like them OK, but the subjects look to me as if they'd fallen into a rouge pot. OTOH, the landscapes, which I'm seeing for the first time on this thread, are wonderful.
Those are probably the ones I'm thinking of. It's probably no coincidence that when I was in art school in the late 60's, they were being very careful to avoid teaching much of anything. This attitude still persists, but seems to be lessening.
I sometimes wonder if I would have left art all these years if I had actually been taught how to see and draw when I was an art major. After graduating from college, I had decided that nobody actually knew how to teach such things - I figured that artists who actually had control of their work must have learned it on their own. I know now that that is not the case.
Meanwhile, though, I'm having a fun time returning to it later in life.