Sense and Nonsense: What We Don’t Know

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A professor I once knew gave history tests in the following format: “Draw a line down the center of the page. On the left side, write what you know on the subject; on the right side, what you do not know.” The logical temptation of such instruction is to put as many things possible on the left side and, on the right, a blank. How can someone be expected to write about what he does not know? The usual case is to write many things about what we do not know but think we know. These are Socratic questions. We should not claim to know what we do not know.

Yet, something fascinating hovers about what we do not know. In general, we may not know something in order to concentrate on what takes much time. We are content, for instance, not to know the interesting geography of Antarctica in order to figure out how to make a better gym shoe or even how to save our soul. The human mind is infinite in what it can know. What usually prevents us from knowing something, besides a certain dullness, is time or proper training.

What substitutes for what I do not actively know? Generally, it is authority. With regard to most of the truths that we actually live by, we accept them on authority. This is as true in matters of daily living as it is true of faith. What, after all, is a map or a blueprint on how to put a toy together but a statement of authority about how something is? The assumption is that the authority knows. Following authority is not the same as acting blindly or in ignorance. Thus, “what we don’t know” does not necessarily paralyze us. We can act on authority to find that it generally works.

On Tuesday, April 18, 1775, Samuel Johnson was at a beautiful Thames villa owned by a certain Mr. Cambridge. Johnson, once in the spacious house library, made a quick run over the books. Johnson overheard Sir Joshua Reynolds, in a loud “aside,” criticize him “for looking only at the backs of the books.” Johnson, as Boswell put it, “ever ready for contest, instantly started from his reverie, wheeled about, and answered, ‘Sir, the reason is very plain. Knowledge is of two kinds. We know a subject ourselves or we know where we can find information about it. When we in-quire into any subject, the first thing we have to do is to know what books have treated of it. This leads us to look at catalogues, and the backs of books in libraries” (I, 595). Even if we do not know something, we know where to go to find it. This is a precious intelligence. Writing down what we do not know on the right side of the exam may have a point after all!


To translate this examining “backs of books” into modern terms, someone recently asked me about “the Illuminati,” about whom I knew little. I went to Google, typed in “Illuminati, Catholic Encyclopedia.” Immediately I found an essay on the topic. The Illuminati were a secret 18th-century society founded by a graduate of a Jesuit college. It figures.

During Christmas, visiting a nephew, I found an elegant edition of Treasure Island. If I read it, I no longer well recall it. I was charmed by it. The sailors on the Hispaniola, I read, were given “duff every other day.” I wondered what this phrase meant. I do recall the colloquial expression “get off your duff.” I remember asking my niece what it might mean. Maybe it meant that the sailors were given light duty every other day. But “getting off one’s duff” usually meant work.

For Christmas, I was once given the Merriam-Webster’s Collegiate Dictionary, tenth edition. When I returned, I went to the “backs of my reference books” to this dictionary. The second entry for “duff” means indeed “buttocks.” The expression “get off your…” is given as an example. The third entry means “something worthless”—a British expression from around 1889.

The first entry for “duff,” however, is from 1816, an alternate to “dough.” It means “a boiled or steamed pudding, often containing dried fruit.” The second sense is “partly decayed matter on a forest floor.” The third sense is “fine coal.” When the sailors were given “duff” every other day, it simply meant that they were given pudding! My mind was at rest.

All of this proves Johnson’s point about the vastness of what we don’t know. We are curious beings. We can look at the “backs of books” until we find one that is likely to inform us. What we don’t know is the beginning of an adventure to take us to what we do know.

Rev. James V. Schall, S.J.


Rev. James V. Schall, S.J., (1928-2019) taught government at the University of San Francisco and Georgetown University until his retirement in 2012. Besides being a regular Crisis columnist since 1983, Fr. Schall wrote nearly 50 books including The Mind That Is Catholic from Catholic University of America Press; Remembering Belloc from St. Augustine Press; and Reasonable Pleasures from Ignatius Press. His later books include A Line Through the Human Heart: On Sinning and Being Forgiven (2016) and On the Principles of Taxing Beer and Other Brief Philosophical Essays (2017). His last books are Catholicism and Intelligence (Emmaus Road, 2017); The Universe We Think In (CUA Press, 2018); Run That By Me Again (Tan, 2018) and The Reason for the Season (Sophia Institute Press, 2018).

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