Why does our language divide up reality one way rather than another? On what rational basis does our language contain certain kinds of general words rather than others? Hirsch shows that a language can be constructed which describes reality in ways we would find absurdly irrational, for example by classifying normally disparate items under the same general term. The apparent irrationality of the new language does not depend on its impoverished fact-stating power, as this may be equivalent to the fact-stating power of ordinary language; the problem then is to explain exactly what is wrong with it. Various options are explored and criticized, such as the hypothesis that language must reflect an underlying objective distinction between 'natural' kinds; that there are pragmatic reasons for the way language functions as it does; and that, as a matter of 'metaphysical necessity,' strange ways of dividing up reality are constructions out of ordinary ways. Having demonstrated that this newly identified problem is in fact a serious one which cannot be easily solved or brushed aside, Hirsch offers his own suggestions for a possible solution.