Three-Valued Logic

Let us make up a logic in which there are three truth-values, T, F, and “M,” instead of the two truth-values T and F. And, instead of the usual rules, let us adopt the following: (a) If either component in a disjunction is true (“T”), the disjunction is true; if both components are false, the disjunction is false (“F”); and in all other cases (both components middle, or one component middle and one false) the disjunction is middle (“M”). (b) If either component in a conjunction is false (“F”), the conjunction is false; if both components are true, the conjunction is true (“T”); and in all other cases (both components middle, or one component middle and one true) the conjunction is middle (“M”). (c) A conditional with true antecedent has the same truth-value as its consequent; one with false consequent has the same truth-value as the denial of its antecedent; one with true consequent or false antecedent is true; and one with both components middle (“M”) is true. (d) The denial of a true statement is false; of a false one true; of a middle one middle.