ABSTRACT
This chapter looks at some more informal questions, and concerned with the oddities of tautological implication and some ideas for avoiding them. From a formal point of view, de Morgan implication may be regarded as a logic that abandons both the law of noncontradiction and the law of excluded third, whilst retaining the law of identity. De Morgan implication, Kaiman implication and tautological implication diverge only in the vicinity of negation. Kaiman implication and tautological implication between them exhaust the direct extensions of de Morgan implication. It is not difficult to transform the relation of tautological implication into an interesting operator. The transformation can be carried out in several ways, but the most elegant is rather indirect. By and large, tautological implication is an unsurprising relation. Different people react in different ways to the Clarence Irving Lewis principles. For some they are welcome guests, whilst for others they are strange and suspect.
