Liberalism Ancient and Modern, Basic Books, 1968.  Reprint: University of Chicago Press, 1995.

Excerpt:

Liberal education is education in culture or toward culture.  The finished product of a liberal education is a cultured human being.  “Culture” (cultura) means primarily agriculture: the cultivation of the soil and its products, taking care of the soil, improving the soil in accordance with its nature.  “culture” means derivatively and today chiefly the cultivation of the mind, the taking care and improving of the native faculties of the mind in accordance with the nature of the mind.  Just as the soil needs cultivators of the soil, the mind needs teachers.  But teachers are not as easy to come by as farmers.  The teachers themselves are pupils and must be pupils.  Btu there cannot be an infinite regress: ultimately there must be teachers who are not in turn pupils.  Those teachers who are not in turn pupils are the great minds or, in order to avoid any ambiguity in a matter of such importance, the greatest minds.  Such men are extremely rare.  We are not likely to meet any of them in any classroom.  We are not likely to meet any of them anywhere.  It is a piece of good luck if there is a single one alive in one’s time.  For all practical purposes, pupils, of whatever degree of proficiency, have access to the teachers who are not in turn pupils, to the greatest minds, only through the great books.  Liberal education will then consist in studying with the proper care the great books which the greatest minds have left behind–a study in which the more experienced pupils assist the less experienced pupils, including the beginners.

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