Compatibility

The lexical relation which corresponds to overlap between classes will be given the name compatibility. The defining characteristics of compatibles (lexical items related by compatibility) are two. The first is that there are no systematic entailments between sentences differing only in respect of compatibles in parallel syntactic positions. So, for instance, if X and Y are compatibles, then A is f(X) and A is not f(X) are logically independent of A is f(Y) and A is not f(Y). This criterion on its own does not guarantee any but the most tenuous relation of sense, since, for instance, harmless is compatible with heavy, and rare with round. The second defining characteristic of compatibility guarantees a genuine relationship of sense: it is that a pair of compatibles must have a common superordinate. Compatibles, therefore, have some semantic traits in common, but differ in respect of traits that do not clash. The relationship is examined by dog and pet. They both fall under the superordinate animal (insense of “creature”); and It’s a dog and It’s not a dog have no necessary links with It’s a pet and It’s not a pet. Another pair of compatibles is husband and policeman; both belong to the category of human males, and Arthur is/is not a husband and Arthur is/is not а policeтап are logically independent.

Two varieties of compatibility can be distinguished: strict compatibility and contingent compatibility. X and Y are strict, compatibles if they have at least one shared hyponym or hyponymous expression which is independently characterisable. Take the case of snake and poisonous creature. It’s a snake entails neither It’s a poisonous creature nor It’s not a poisonous creature; likewise It’s a poisonous creature is logically independent of It’s a snake. Snake and poisonous creature are strict compatibles because adder and cobra, for instance, are hyponymous to both; furthermore, these species are independently characterisable — that is, they are not established solely on the basis of venomousness. (Adders and cobras are not, of course, necessarily venomous, only canonycally so, since any individual snake may have had its venom extracted). Contingent compatibility is more common. It is exemplified by dog and pet: every dog is, in principle, a potential pet. There is no independently characterisable subclass of dogs for which being a pet is a necessary or canonical trait (lap-dogs do not count, because they cannot be distinguished without invoking the characteristic of pet-hood); nor are there distinguishable sub-types of pet which are canonically or necessarily dogs (except, of course, lap-dogs, which do not count here, either, and for parallel reasons).