The algorithm terminates in one of two cases. Either the CNF formula Φ is found to comprise a "consistent set of literals"—that is, there is no codice_3 "and" codice_14 for any literal codice_3 in the formula. If this is the case, the variables can be trivially satisfied by setting them to the respective polarity of the encompassing literal in the valuation. Otherwise, when the formula contains an empty clause, the clause is vacuously false because a disjunction requires at least one member that is true for the overall set to be true. In this case, the existence of such a clause implies that the formula (evaluated as a "conjunction" of all clauses) cannot evaluate to true and must be unsatisfiable.