Spirit.

 O'Keeffe, Blue, Black, and White Abstraction #12, 1959

That which they call abstract is the most realistic, because what is real is not the exterior but the idea, the essence of things. 

When you see a fish you don't think of its scales, do you? You think of its speed, its floating, flashing body seen through the water... If I made fins and eyes and scales, I would arrest its movement, give a pattern or shape of reality. I want just the flash of its spirit.

- Constantin Brancusi