The still life represents a moment of technical perfection.  Artists can paint anything.  They can paint clear glass. They can paint clear water. They can paint clear water in a clear glass.  They can paint a drop of clear water sliding down the side of  a  crystal clear glass full of clear water. 
The still life is a showroom of all the incredible things artists can do with paint. They have answered the question “What can you paint?”
The new challenge is what SHOULD you paint?

Citation
​Helda, W. (1662) Still-Life. Private collection.
​http://www.wga.hu/frames-e.html?/html/h/heda/index.html