But which one of us hasn’t at one time or another wished on a birthday cake candle, pulled on a wishbone for good luck, tossed a coin into a wishing well, knocked on wood, crossed our fingers for good luck (or when we told a lie), shunned opening an umbrella in a house (lest bad luck rain on us), felt happy at finding a four-leaf clover, or said, “Gesunheit” or “God bless you” to someone who sneezed?