Francis Schaeffer traced the decline of civilization through its art. Some readers protested when their favorites—Kierkegaard, Stravinsky, Camus—ended up on the wrong side of Schaeffer's "line of despair," which illustrates the danger of trying to impose absolute standards on art. Still, we all sense that something has changed in Western civilization, and probably not for the better. Merely listen to a Bach motet, a Beethoven symphony, a Shostakovich concerto, and a meditation by John Cage—in that order.

I once spent several leisurely hours in the manuscript room of the British Museum, grazing through the centuries from Shakespeare and Donne to Elizabeth Barrett Browning, Jane Austen, and Virginia Woolf. As I approached the twentieth-century displays, I could not avoid the sensation of sliding downhill. The handwriting, subject matter, and even the sentence structure seemed to deteriorate. Finally I reached the most recent manuscripts, featuring the scrawled original of a renowned Beatles' song: "Oh yeah, oh yeah, I wanna hold your hand." A long descent from John Donne.

I took a fascinating graduate course from the University of Chicago on "The History of the Structure of the English Sentence." Beginning with the very earliest writings, we analyzed representative sentences from different eras. By the end of the course, students could date an unidentifed paragraph within a half-century simply by diagramming its sentences. Grammatical structure, it turns out, yields an important clue to overall culture.

In societies secure in truth, reason, and their role in the world, writers tend to produce balanced, confident sentences. Samuel Johnson did not mentally diagram his sentences before speaking, to ensure that ...