Abstract
Mally succeeded in developing two theories of properties, passing from the distinction between Sein and Sosein (1904) to the theory of nuclear and extranuclear properties (1912). According to the first one, the Sein of an object depends on the Sosein of the object, whereas the Sein of the Sosein of an object does not depend on the Sein of the object. These Principles allow the distinction between possible and impossible objects (in respect to Sosein) and between real and ideal objects (in respect to Sein). In his second theory, Mally distinguishes between first order properties that determine the object, and higher order properties, like difference or simplicity, ending with the distinction between impossible objects and non-satisfiable objects.