What Does it Mean to be 'Irrational'?

The Anti-Vax Movement and the Limits of Reason

“Rationality” and “reasonableness” are notoriously difficult words to define, because they rely on circular reasoning. Rationality requires, well, “being agreeable to reason” or “common sense.” Fair enough. But this only raises more questions. In a society as divided as ours, who exactly decides what is held in common or what is sensible? Reason itself …