Published online by Cambridge University Press: 12 March 2014
In [1], William H. Jobe has shown that a certain three-valued proper logic is canonically complete, i.e., each first order J is expressible by a formula that is in M-normal form. The first order operator Jk(p)1 represents the truth table of a possible formula which has the truth value k in the ith row and the truth value 1 in all other rows. “The M-normal form of a given formula is another formula which has the same truth table as the given formula but which contains no operation symbols other than those of conjunction, disjunction, and undefined unary operations, with no nonunary operation, i.e., conjunction or alternation, included in the scope of an operation which is unary, and no alternation included in the scope of a conjunction.” Here it is shown that it is possible to construct a canonically complete proper logic for each choice of M which contains, in addition to alternation and conjunction, exactly two unary operations. Moreover, it is further shown that at least two unary operations are necessary in order for such a logic to be canonically complete.