Justification

This is the least self-evident of our axioms. It can be made more evident by considering an empty Venn or Carroll diagram for three terms and their negations: the three out of eight cells indicated by the left-hand side of the identity are the same as those picked out by the right-hand side, namely the cells for *abc*', *ab*'*c* and *ab*'*c*'. Given the De Morgan definition of Term Addition ADD below, it permits the derivation of the desirable distribution laws DIST1 and DIST2 below.

3.2.2. Extensional

for N and Λ HEID NΛ (Heidegger's Law)
