Henderson only showed that a prime number of sets is necessary, not that you can always design a symmetric Venn diagram for every prime number. Thus began a contest to find larger and larger examples.

Venn used the diagrams to prove a form of logical statement known as a categorical syllogism. This can be used to model reasoning. Here’s an example: “All computers need power.

April 2023 marks the 100th anniversary of the death of mathematician and philosopher John Venn. You may well be familiar with Venn diagrams – the ubiquitous pictures of typically two or three ...