The study of language has a long and rich history, extending over thousands of years. This study has frequently been understood as an inquiry into the nature of mind and thought on the assumption that" languages are the best mirror of the human mind"(Leibniz). A common conception was that" with respect to its substance grammar is one and the same in all languages, though it does vary accidentally"(Roger Bacon). The invariant" substance" was often taken to be the mind and its acts; particular languages use various mechanisms-some rooted in human reason, others arbitrary and adventitious for the expression of thought, which is a constant across languages. One leading eighteenth century rational grammarian defined" general grammar" as a deductive science concerned with" the immutable and general principles of spoken or written language" and their consequences; it is" prior to all languages," because its principles" are the same as those that direct human reason in its intellectual operations"(Beauzée). Thus," the science of language does not differ at all from the science of thought."" Particular grammar" is not a true" science" in the sense of this rationalist tradition because it is not based solely on universal necessary laws; it is an “art” or technique that shows how given languages realize the general principles of human reason. As John Stuart Mill later expressed the same leading idea," The principles and rules of grammar are the means by which the forms of language are made to correspond with the universal forms of thought.... The structure of every sentence is a lesson in logic." Others, particularly during the Romantic period, argued that the nature and content of thought are determined in part by the devices made available for its expres-