Can you solve it? The enduring appeal of Venn diagrams

John Venn 1834-1923 John Venn – the British logician who around 1880 devised the ‘Venn diagram’ – celebrates his 185th birthday this week. His idea, a brilliantly simple visual aid to understanding logical relations, is one of the few concepts from abstract mathematics that is easily understood, and regularly used, by non-mathematicians. Indeed, only last…