ABSTRACT
A t the beginning of Chapter 1, the positive connectives and, or and i f - then were given a deductive interpretation. Just as these connectives do, also negation refers to a semantical meaning, namely that something is so or is not so. But which something is it, to which not might refer w ith respect to deductive situations ? W hat shall it mean that a deduction leads from M to not v :
(a ^ M = 4 -iv .
