A baseball bat and a ball combined cost 1 dollar and ten cents. The bat costs a dollar more than the ball. How much does the ball cost?
You should give your answer before you have time to read this sentence, and if you already have read it, you have completely ruined everything and and you are an absolute waste to society.
ANYWAY, if you did answer the question quickly, like I did today when it was posed to me, and apparently like 55% of Harvard grads did as well, you probably answered incorrectly. You probably said that the ball costs 10 cents. But this is not an algebra question. The issue the question raises is whether we can ever really trust our own reasoning. If we make simple computational errors like this all the time, which we probably do, then how can we be so sure that any conclusions we come to are ever objectively right?