A Brief Proof of the Full Completeness of Shin’s Venn Diagram Proof System

In an article in the Journal of Philosophical Logic in 1996, “Towards a Model Theory of Venn Diagrams,” (Vol. 25, No. 5, pp. 463–482), Hammer and Danner proved the full completeness of Shin’s formal system for reasoning with Venn Diagrams. Their proof is eight pages long. This note gives a brief five line proof of this same result, using connections between diagrammatic and sentential representations.