The magician's code
The convention among stage magicians not to reveal how tricks are done, which keeps the art alive.
Also: magicians' code, secrecy of stage magic, never reveal the secret
Stage magicians agree, as a matter of professional ethics, not to expose methods to the public, not to perform another's original effect without permission, and not to repeat a trick to the same audience. The rule is not law, but it shapes the trade, and societies such as the Magic Circle (founded in London in 1905) and the Society of American Magicians (1902) include it in their codes. The principle rests on the idea that the audience agrees to be fooled, so that the performance is honest, unlike a medium who claims real powers. This is why this site discusses the history, theory and effects of stage magic, such as misdirection, without giving away how particular tricks work.