There is more, but that would make this post into a spoiler.'I do believe it,' he said. 'I believe every word you say.'She shook her head.'You can't in the face of the evidence.''I believe it.''No. You may persuade yourself for the moment that you do, but after a while you will have to go by the evidence. You won't be able to help yourself. You haven't realized what a crushing thing evidence is. You have to go by it against your will. You see, evidence is the only guide. You don't know that I am speaking the truth; you just feel it. You're trusting your heart and not your head. The head must win in the end. You might go on believing for a time, but sooner or later you would be bound to begin to doubt and worry and torment yourself. You couldn't fight against the evidence, when once your instinct—or whatever it is that tells you that I am speaking the truth—had begun to weaken. And it would weaken. Think what it would have to be fighting all the time. Think of the case your intelligence would be making out, day after day, till it crushed you. It's impossible that you could keep yourself from docketing the evidence and arranging it and absorbing it. Think! Consider what you know are actual facts. ...'
Actually, I think Elizabeth (the female speaker) underestimates the power of volitional belief.