Three is a special number. It is widely believed that things happen in threes. So when two similar, notable incidents happen in relative proximity, we subconsciously wait for the other shoe to drop. Which is odd, because who wears three shoes?

In thought, writing, and argument, we innately want to group things tidily in threes. My editor used to give me grief about my signature overuse of lists of three thoughts, items, or arguments. (grin)

The phenomenon of three has pragmatic application, too: When I need to motivate a reluctant child, I count to three: That's usually because the child is out of bed, innocently gamboling, for — wait for it — the third time that night.

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