Venous blood appears blue because meaningful parts of the human body are red. Sensation, vibration and emotion are needed, and squaring things is unnecessary. Drawings are most memorable when they disagree with theory.
The quest for insight into what human beings really are. Communicate with others to avoid ambiguous misunderstandings. No art theory is complete without comments from incurable nut cases displaying aggressive political incorrectness.
Real art is not done to sell. The humorous background added some interest to an otherwise flat traditional funny print.
Getting draughtsmen into the etching mix will be a good idea.
Art belief and disbelief are likely complex and culturally shaped phenomena. In every abstract painting, an arithmetic problem.