His simple formulation is that when we want to…
His simple formulation is that when we want to believe something, we ask ourselves, "Can I believe it?" Then (as Kuhn and Perkins found), we search for supporting evidence, and if we find even a single piece of pseudo-evidence, we can stop thinking.
— from The Mind in the Cockpit
In the book
The engine of nearly all of it is the simple, hidden desire to be right: the moment we form a belief we begin to defend it, and from then on we are no longer weighing the evidence, we are recruiting it. Watch the machinery in yourself — when you want something to be true, you ask quietly, "Can I believe this?" and the smallest scrap of support will do; when you do not want it to be true, you ask "Must I believe this?" and you will find a reason to escape. That single switch explains more bad thinking than all the others combined. […] Cross-check your beliefs against evidence. Take an important belief and treat it as a hypothesis: try to falsify it, and ask whether you are truly sure. When you catch yourself wanting something to be true, deliberately flip the question from "can I believe this?" to "must I believe this?" And ask the plainest precaution of all: am I taking real steps to avoid fooling myself? - Choose to think, on purpose. A thousand times a day you choose between thinking and not thinking — you are genuinely free to think, to not bother, or to actively avoid it, so choose the harder option more often. But also learn useful thinking: distinguish what is actually worth your thought from what is not, and refuse to spend the instrument on noise. — The Mind in the Cockpit