What Is Wrong With Precision in Poetry?
The father of the computer meets Tennyson.
Posted February 28, 2020
Tennyson has a poem, "The Vision of Sin," which contains the lines: "Every moment dies a man, Every moment one is born." Polymath Charles Babbage (inventor, engineer, and mathematician, considered by some the "father of the computer") after reading the poem wrote a letter to Tennyson, suggesting that the verse contains a mathematical inaccuracy and must be changed:
In your otherwise beautiful poem "The Vision of Sin," there is a verse which reads—"Every moment dies a man, Every moment one is born." It must be manifest that if this were true, the population of the world would be at a standstill. In truth, the rate of birth is slightly in excess of that of death. I would suggest that in the next edition of your poem, you have it read—"Every moment dies a man, Every moment 1 1/16 is born." The actual figure is so long I cannot get it onto a line, but I believe the figure 1 1/16 will be sufficiently accurate for poetry. 
Babbage may have been facetious, but his letter raises a serious question: Why can't you change the line (except, perhaps, in writing a poem for an exceptionally geeky sweetheart)? There seems to be such a thing as "too precise for poetry," but why is that?
Now, it is not difficult to see why inaccuracy may be permitted in art: An inaccuracy may be helpful in achieving one's artistic goals. This is true of many types of inaccuracies, historical, factual, or scientific.
Consider, for instance, the case of Golding's Lord of the Flies.  As Julian Barnes points out in his novel Flaubert's Parrot, there is an inconsistency between two claims made in Golding's book: One is that the character Piggy is nearsighted; the other is that Piggy's glasses are used as burning lens, which can only be done if he were farsighted. But the plot needs Piggy to be nearsighted, and the burning lens bit is important also.
Golding may or may not have known there was a scientific inaccuracy in the book, but even if he did, he had artistic justification for leaving that in. Yet all this shows is that inaccuracy may be permitted. And our intuitive response to Babbage's urging Tennyson to change the poem suggests something stronger: We think inaccuracy may be not simply allowed but required.
A poem ought not to be too precise. Why? What makes precision—or certain kinds of precision—bad in poetry?
Actually, what we object to in Babbage's version of the line is not really precision but the appearance of precision. For note that the precision of Babbage's revised line is mostly apparent, and to the extent it is there, it is ephemeral.
The birth and death rates in the world fluctuate, so if you wanted to get the numbers right, you'd have to explain when exactly the rate was as you say. (Or perhaps—something Babbage could not have foreseen—you can use software that updates the line constantly.) And you'd have to take out the word "every" also since the ratio would apply only to a particular minute. More importantly, you cannot use "man" (or "woman," for that matter) either, since no one comes into the world as a grown adult. No man is ever born, not this minute and not at any other time.
But what is wrong with the appearance of precision?
The answer, I think, has to do with the fact that we expect poetry to leave us with the impression it's "come from the heart." In actual fact, we want poetry to be good, and it won't be very good if it really came from the heart (think of all sincere but bad love poems), but we expect the poet to disguise the involvement of the analytical mind and to make it look like his or her emotions rose up in the chest and splattered a poem on the white sheet. It would be difficult to maintain this impression if the poet included numbers that look precise, whether or not they actually are. Controlled thinking processes would then be too obvious and salient.
There is an important qualification to make here. A given author may use precision—indeed, clinical precision—to great aesthetic benefit. Upon occasion, what moves the reader may be precisely that the author is adopting a detached, clinical tone, leaving ample room for the reader's own emotions.
Consider, for instance, the beginning of a short piece called "Autopsy Report" by Peggy Shumaker. The piece is not exactly a poem, but it is poetic. It begins thus:
My mother's brain weighed 1420 grams.
No discernible measure for the gravity of her mind.
Her thoughts, heavy enough to crush her. 
It seems to me Babbage could not disapprove. And I would conjecture: neither would Tennyson.
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 Bernstein, J. (1964). The Analytical Engine: Computers, Past, Present, and Future. New York, NY: Random House.
 Barnes, J. (1984). Flaubert's Parrot. New York, NY: Vintage Publishing.
 Shumaker, P. (2020). "Autopsy Report," Sunday Short Reads #068. Available at: https://www.creativenonfiction.org/form/sunday-short-reads