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The Principia Mathematica propositional logic page proves many propositional logic theorems from axioms. It is based on Principia Mathematica by Alfred North Whitehead and Bertrand Russell. Published in 1910, Principia was an attempt to build all of mathematics on a rigorous axiomatic basis. Some parts of its treatment, like the set theory based on type theory, have not been widely adopted. Yet a hundred years after its publication, the propositional logic part of the book remains one of the most cited sources for theorems in propositional logic. Its axiomatic basis consists of two indefinable logical connectives, negation and disjunction, five logical axiom schemata and one rule of detachment, modus ponens.