Henri Poincaré Quote
How does it happen that there are people who do not understand mathematics? If mathematics invokes only the rules of logic, such as are accepted by all normal minds; if its evidence is based on principles common to all men, and that none could deny without being mad, how does it come about that so many persons are here refractory?
The Foundations of Science, Science and Method, Book I, Chapter III (p. 383), The Science Press. 1913