Commutativity of conjunction
In propositional logic, the commutativity of conjunction is a valid argument form and truth-functional tautology. It is considered to be a law of classical logic. It is the principle that the conjuncts of a logical conjunction may switch places with each other, while preserving the truth-value of the resulting proposition. Formal notation Commutativity of conjunction can be expressed in sequent notation as: and where is a metalogical symbol meaning that is a syntactic consequence of , in the one case, and is a syntactic consequence of in the other, in some logical system; or in rule form: and where the rule is that wherever an instance of "" appears on a line of a proof, it can be replaced with "" and wherever an instance of "" appears on a line of a proof, it can be replaced with ""; or as the statement of a truth-functional tautology or theorem of propositional logic: and where and are propositions expressed in some formal system. Generalized principle For any propositions H1, H2, ... Hn, and permutation σ(n) of the numbers 1 through n, it is the case that: H1 H2 ... Hn is equivalent to Hσ(1) Hσ(2) Hσ(n). For example, if H1