There’s a little mental game I like to play when I find myself forming an opinion, making a big decision, or investing intellectually in a particular belief. I like to ask myself: “what would make me believe otherwise?”
If I can’t think of what would make me change my mind, then I back off from formalizing the decision. I’m not ready. I’m being emotional, irrational, and biased. It’s one thing to say, “I have this opinion because I believe it’s true,” but it’s quite another to say “here is the specific evidence I would need to believe the opposite.” Most of the time, we’re not prepared to do that.
The Opportunity Machine 