Prägnanz is definitely a cardinal concept in Gestalt theory, but, as Kanizsa and I have stressed in the last ten years (Kanizsa and Luccio, 1986, 1987, 1990, 1993, 1995), it has nevertheless given rise to a number of misunderstandings. The Gestaltists have often been criticised for having turned Prägnanz into a key to open all doors, without ever having given it a strict definition. The concept was introduced by Wertheimer (1912) in his essays on thought processes in primitive peoples in which he speaks of privileged, ausgezeichneten or "prägnant" zones in numerical series. However, Wertheimer spoke of a "law of Prägnanz" only two years later, affirming that, amongst many "Gestalt laws" of a general type, there is a "Tendenz zum Zustandekommen einfacher Gestaltung (Gesetz zur "Prägnanz der Gestalt') (Wertheimer, 1914).