Abstract
Chomsky has constructed an empirical theory about syntactic universals of natural language by defining a class of 'possible languages' which includes all natural languages (inter alia) as members, and claiming that all natural languages fall .within a specified proper subset of that class. I extend Chomsky's work to produce an empirical theory about natural4anguage semantic universals by showing that the semantic description of a language will incorporate a logical calculus, by defining a relatively wide class of 'possible calculi', and by specifying a proper subset of that class which, I hypothesize, includes the calculi needed for the semantic description of any natural language. I argue that the special status, with respect to natural languages, of this particular type of logical calculus is an empirical finding which does not follow from any independently-known principles, and I conclude that the question why the laws of human thought have the structure they do is a biological rather than a logical question