John Stuart Mill on grammar and Logic

"Grammar is the most elementary part of Logic. It is the beginning of the analysis of the thinking process. 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 distinctions between the various parts of speech, between the cases of nouns, the modes and tenses of verbs, the functions of participles, are distinctions in thought, not merely in words. The structure of every sentence is a lesson in Logic."
John Stuart Mill, Rectorial Address at St. Andrews, 1867, quoted from Jespersen, The Philosophy of Grammar, London, 1924, p. 47.