“Is anyone there? Can you hear me?” You shout at the rubble of a collapsed building. No reply, but then… was that tapping?

You have an idea. “If you can understand me,” you yell, “tap once.” A single tap. “If you’re injured,” you then say, “tap twice.” Two taps. There’s someone there.

An apt metaphor for something very important. To read what, please click here.