Full Idea
Venn Diagrams are a traditional method to test validity of syllogisms. There are three interlocking circles, one for each predicate, thus dividing the universe into eight possible basic elementary quantifications. Is the conclusion in a compartment?
Gist of Idea
Venn Diagrams map three predicates into eight compartments, then look for the conclusion
Source
David Bostock (Intermediate Logic [1997], 3.8)
Book Reference
Bostock,David: 'Intermediate Logic' [OUP 1997], p.124