illusions teach us how to think about error. Intellectually, they show us how even the most convincing vision of reality can diverge from reality itself, and how cognitive processes that we can’t detect—and that typically serve us quite well—leave us vulnerable to mistakes. Emotionally, illusions are a gateway drug to humility. If we have trouble acknowledging our own errors and forgiving those of others, at least we can begin by contemplating the kind of mistakes to which we all succumb.
