This isn't set theory. (Venn diagrams can be interpreted in a set theoretic way, but this isn't particularly useful within set theory itself, and the symmetric

This isn't set theory. (Venn diagrams can be interpreted in a set theoretic way, but this isn't particularly useful within set theory itself, and the symmetric and simple properties of the Venn diagram are unnecessary for this interpretation. We've had a construction for a simple Venn diagram of n curves since Venn's original paper -- it's the symmetry that's new.)