 The system of propositional logic of PM, can be seen as a system of sentential logic consisting of a language, and rules of inference. PM contains the first presentation of symbolic logic that deals with propositional logic as a separate theory. Frege had involved quantification from the beginning, while Peano’s system was interpretable as about propositions and classes with some different principles holding for each interpretation. The propositional logic of PM is unusual for modern readers, for various reasons having to do with its origins in Russell’s earlier work on logic. One is that the axioms of propositional logic are not stated using only the primitive connectives of the logic, which are \(\lnot\) and \(\lor\), but instead only use \(\lor\), and \(\supset\) which is a defined connective.