It is the mark of an educated mind to be able to entertain a thought without accepting it.

Holding an idea at arm’s length and examining it, without either adopting it or fighting it off, is an unusual skill. Most of us do both at once: we hear a claim and immediately sort it into ally or threat, which means we never actually look at it. The ability to sit with a possibility you may reject is what makes it possible to change your mind on evidence rather than under pressure.

Take a position you dislike and spend ten minutes constructing the best case for it, without conceding anything. The point is not to be persuaded. It is to find out whether your disagreement was ever examined.