His answer is to look for hints. If an idea that looked preposterous before, it makes sense now, we have a change and we have an opportunity. He borrows the words from Linda Rottenberg's book - Crazy is a Compliment - to describe how they select the funding for new startups in Y Combinator. Rather that debate over and over over new idea, as we do on twitter most of of the time, we should bet on this idea.
In Kabbalah, there are interpretations that mirror the idea of Paul Graham. Here is quote from the kabbalist Rav Yitzchak Ginsburgh. Rav Ginsburg is an University of Chicago graduate in mathematics and philosophy and now is a highly respected teacher of Kabbalah in Jerusalem.
The beginning of turning the world upside down begins with turning my own world upside down and revealing the yechidah in my psyche. "World" in Hebrew means "concealment." The people walking in darkness saw a great light. People itself עם also means darkness. Each one of us is in darkness and we are walking in darkness, and we have to turn upside down and shine a great light. The light that comes out of darkness is infinitely much stronger and more essential than direct light. That is why the Almighty created the world in a manner of "first darkness and then light," so that the great light would shine. Thank God, as it were, we have a lot of darkness, and now is the time for the great light to shine through this darkness. this truth that is in each one of us is what needs to shine through.So the one kabbalistic answer to the question: "Can you protect yourself against obsolete beliefs?" is: "Yes by turning the visible world - which hides the real world - upside down. Then we turn ourselves upside down and see the light within the darkness."