"A proof is that which convinces a reasonable man; a rigorous proof is that which convinces an unreasonable man."

Next Quote

In an argument, you may silence your opponent by pressing an advantage of strength or of wealth, or of education. But you do not really convince him. Though he is no longer saying anything, in his heart he still keeps to his opinion, the only way to make him change that opinion is to speak quietly and reasonably. When he understands that you are not trying to defeat him, but only to find the truth, he will listen to you and perhaps accept what you tell him.

— Kano Jigoro