What would a Martian visitor think to see a human being laugh? It must look truly horrible: the sight of furious gestures, flailing limbs, and thorax heaving in frenzied contortions. The air is torn with dreadful sounds as though, all at once, that person wheezes, barks, and chokes to death. The face contorts in grimaces that mix smiles and yawns with snarls and frowns. What could cause such a frightful seizure?

A word can only serve to indicate that someone else may have a valuable idea—that is, some useful structure to be built inside the mind. Each new word only plants a seed: to make it grow, a listener's mind must find a way to build inside itself some structure that appears to work like the one in the mind from which it was “learned”.