|Calculus: a calculus is a system of symbols for objects (which are not further specified) as well as rules for the formation of expressions by the composition of these symbols. There are other rules for transforming composite expressions into other expressions. As long as no specified objects are accepted for the individual symbols, the calculus is not interpreted, otherwise interpreted.|
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|Berka I 505
Calculus of classes / Tarski: satisfaction by sequences of objects.
Logic, Semantics, Metamathematics: Papers from 1923-38 Indianapolis 1983
K. Berka/L. Kreiser
Logik Texte Berlin 1983