Doubt?

"That's the problem with seeing things. Nothing is clear. Feelings, ideas shape what's in front of you. Cézanne wanted the naked world, but the world is never naked. In my work, I want to create doubt." He stopped and smiled at me. "Because that's what we're sure of."
~ Siri Hustvedt (What I Loved)

...and again there is the uncertainty of the question mark. the issue of what to mark. and the decisions of what is worth bringing up at all ...marked or not