Irving Kristol, "The Philosophers' Hidden Truth," Commentary Magazine, October 1952.
It is to the answering of this question, and not only with regard to Plato but also as it affects all pre-Enlightenment thinkers of significance, that Professor Leo Strauss—distinguished occupant of the Charles Merriam chair of political science at the University of Chicago and guest professor at the Jewish Theological Seminary’s Institute on Theology—is devoting himself. It is his thesis that few, if any, of the Great Books in philosophy and political philosophy written before the French Revolution inaugurated the era of journalism can simply be “read,” no matter how vigorously the student (or the instructor) is exhorted to do so and no matter how earnestly he applies himself. They have to be studied, and in a special way; for if they are truly great, it is probably their intention to conceal as well as to reveal, and they do not yield their secrets easily. In other words, the Great Books contain, besides their exoteric teachings as piously summarized in textbooks, esoteric doctrines reserved only for the most intelligent and perceptive. It must be admitted that this sounds rather preposterous— but only until one has read Professor Strauss, after which it appears astonishingly plausible.