For some years before the outbreak of World War I, a number of painters in different European countries developed works of art that some have described as prophetic: paintings that by challenging viewers’ habitual ways of perceiving the world of the present are thus said to anticipate a future world that would be very different.
Topic
some pre-WWI painters in Europe who broke heavily with representational Renaissance styles and whose works some described as prophetic.
Framework
Challenge a Position
Main Point
The idea that these painters should be credited with predicting the future and primarily celebrated for that is dumb. They should primarily be celebrated for their artistic innovations.
P1 - Introduction to topic
We're told about a group of artists in a certain time period that set themselves apart by breaking with customary styles, and whose art was described by some as prophetic.
P2 - The opposing position
We're told about critics who are so impressed by the "break with tradition" in this art that they think the artists predicted not only future art but just the real world future. One dude even says,
P3 - Author's Challenge begins
After making a concession that there were probably some "accidentally" prophetic elements to the work of some of these artists, the author cites evidence drawn from these artists and their friends talking about them, to establish that these guys were not interested in trying to predict the future. They were obsessed with formal aesthetic questions, like (#PicassoBurn)
P4 - Author's Challenge continued (Delacroix example)
This paragraph, to me, is very rhetorically weak, but the author is essentially just trying to show how sometimes artists can have a revolutionary style even when the world doesn't change to then meet their "predictions". It's a very thinly related analogy with almost no logical force towards the author's main point.
Summary
By the end of the first paragraph, we know the topic but not what we're doing with it.
By the end of the second paragraph, we've gotten some hints that we might be Challenging a Position because we're seeing more attributions like "these artists are often credited" / .
We're expecting a PIVOT into disagreement after that sort of attribution.
The 3rd paragraph instead begins with a concession wind-up: No will deny that [part of what you said is fine], but ....
So the Most Valuable Sentence is that first Purpose Pivot (but, yet, however, recently): But forward-looking quality should be credited to their aesthetic innovations rather than their power to guess political/social trends.
The Pivot word helps us hear the author entering center stage. The fact that the following answer begins "for example" shows that our author is now trying to support this Big Idea.