A man in a town married twenty women. There have been no divorces or annulments, and everyone in question is still alive and well. The man is not a bigamist, and he has broken no laws. How is this possible? This is the so-called marrying-man problem, which psychologists often use to study creative insight: the process by which we suddenly figure out the answer to something that had previously stumped us. A problem makes no sense at first. But then we turn it around in our minds and, presto, the answer comes. So, naturally, Mark Beeman, a cognitive neuroscientist at Northwestern University, who studies insight and creativity, likes to pose questions like this one to applicants who want to work in his lab. (The answer to this particular conundrum is that the man is a priest.) Beeman studies insight because it’s a key component in how creativity works—the main subject of his research. Creativity is the whole process of how we come up with new ideas; insight is just a step along the way, albeit an important one. A composer who writes a new, beautiful song has done something creative; the moment when she realized that she could end it on a minor chord was insight. In general, creativity seems to come when insight is combined with the hard work of analytical processing. A person can’t discover the theory of general relativity in a dream if he isn’t a physicist who’s done some heavy thinking about the subject beforehand.