ABSTRACT
This chapter begins by considering the two opposite relations of compatibility and incompatibility. Compatibility is a very general relationship between propositions. The logician is mainly interested in the more specific relationships which may hold between propositions which are compatible. The relation of bare compatibility cannot afford a basis for inference, nor provide the material for a joke. Two characteristics are incompatible when the presence of one necessitates the absence of the other, and conversely. Reasoning is possible because the truth of one proposition is not independent of the truth of all other propositions. Propositions may be compatible without being so related that it is possible to infer the one from the other, or to infer from the truth, or falsity, of the one to the truth, or falsity, of the other.
