An old riddle asked by the mystics of many religions—the Zen Buddhists, the Sufis of Islam, or the rabbis of the Talmud— asks: “Is there a sound in the forest if a tree crashes down and no one is around to hear it?” We now know that the right answer to this is “no.” There are sound waves. But there is no sound unless some-one perceives it. Sound is created by perception. Sound is communication. This may seem trite; after all, the mystics of old already knew this, for they, too, always answered that there is no sound unless someone can hear it. Yet the implications of this rather trite statement are great indeed. It means that it is the recipient who communicates. The so-called communicator, that is, the person who emits the communication, does not communicate. He utters. Unless there is someone who hears, there is no communication. There is only noise. The communicator speaks or writes or sings—but he does not communicate. Indeed he cannot communicate. He can only make it possible, or impossible, for a recipient—or rather percipient—to perceive.

-- Peter F. Drucker, A Functioning Society