 As all these relations are derived from compatibility and its negation, it is possible to represent them in the form of a genealogical tree (see Šebestík 1992: 174). Simplifying somewhat, we can define Bolzano’s relations for pairs of ideas in the language of set theory as shown below. (Here, we depart from Bolzano by also admitting universal ideas such as “something in general” [Etwas überhaupt], along with objectless ideas and the empty set as their extension (for Bolzano, an objectless idea has no extension, and there are no empty collections)). 