I will have spent my life trying to understand the function of remembering,
which is not the opposite of forgetting, but rather its lining.
We do not remember, we rewrite memory much as history is rewritten.
How can one remember thirst?
-the narrator of Chris Marker's 1983 film Sans Soleil
For now, and I can't imagine forever, the entirety of - I won't say the best, because I don't know what that means - the most thought provoking film I know of is available on YouTube.
Chris Marker's Sans Soleil is not non-narrative filmmaking so much as it is several narrative filmmaking, and I would suggest that you follow as many of the threads as beckon to you. It is a film that is akin to the bar described within it, "the kind of place that allows people to stare at each other with equality: the threshold below which every man is as good as any other, and knows it." Each time someone avoids looking at someone else on a sidewalk of New York, I think about recommending that they watch this film. Each year it seems like less people do watch it.