The passage explains that value “may be used purely to describe objects, or they can be used to evoke emotional responses in the viewer.” (page 49) Isn’t one of the main points of art to “evoke emotional responses in the viewer”?

Also, I don’t understand what Robert Ryman’s Winsor 6 is supposed to be. It makes me think of a piece of paper. The passage doesn’t tell us what it actually is. Why is it a piece of art?