A Euler diagram resembles a Venn diagram, ... We've just proven it mathematically. I have a theory that the only thing cartoonists bothered learning in math class was Venn Diagrams.

Euler’s diagrams were effective, but Venn soon realized that they were limited in their applicability. ... He knew there had to be more to math than just cranking through problems.

I haven’t done a roundup of Venn diagrams in several years. That’s a graph that shows sets and all possible overlaps of those sets. It works two-dimensionally when there are three or fewer sets.