Editing Method of analytic tableaux (section)

=== Definitions ===
Assume an infinite set <math>PV</math> of [[propositional variable]]s and define the set <math>\Phi</math> of formulae by induction, represented by the following grammar:

:<math>\Phi ::= PV \mid \neg \Phi \mid (\Phi \to \Phi) \mid (\Phi \lor \Phi) \mid (\Phi \land \Phi)</math>.

That is, the basic connectives are: [[negation]] <math>\neg</math>, [[Material conditional|implication]] <math>\to</math>, [[Logical disjunction|disjunction]] <math>\lor</math>, and [[Logical conjunction|conjunction]] <math>\land</math>.

The truth or falsehood of a formula is called its truth value. A formula, or set of formulas, is said to be '''satisfiable''' if there is a possible assignment of truth-values to the [[propositional variable]]s such that the entire formula, which combines the variables with connectives, is itself true as well.<ref name=":1" /> Such an assignment is said to ''satisfy'' the formula.<ref name=":0" />