“Short, O short then be thy reign/ And give us to the world again!” That’s the great Samuel Johnson, flinging his defiance at sleep during one of his famous nocturnal excursions, in 1753. The storied man of en­ment.

Sleep in the pre-caffeine era was different in quantity and character. In 1630, a sermonizing John Donne told the king of England that sleep was “shaking hands with God,” reflecting the general view that slumber opened the door to contact with the divine. Schmidt says that in the days before caffeine—and advances in lighting and mechanical clocks, which also came along in the mid-17th century—people slept for eight hours, often punctuated by a waking interval of an hour or so that established a more intimate connection to the world of spirits.

By Johnson’s time, however, sleep seemed almost a sin. In 1728, clergyman John Law denounced it as “the poorest, dullest refreshment of the body,” one that produced either “insensibility” or “the folly of dreams.” He excoriated the Christian who chose to “enlarge the slothful indulgence of sleep, rather than be early at his devotions to God.” A few years later, Benjamin Franklin famously reminded slugabeds that time is money. In 1798, John Wesley, the founder of Methodism, advised his followers that six hours of sleep a night was sufficient. He also commissioned an oversized teapot from Josiah Wedgewood.

Coffee and tea permeate the Enlight­enment’s intellectual scene. Many of the era’s leading figures can be seen reading and writing far into the night, feverishly chipping away at the old order’s verities. Johnson himself was known to polish off 24 cups of tea at a sitting. Alexander Pope complained that he could not sleep (“Fools rush into my Head, and so I write”), and William Hogarth’s prints are littered with sleep-deprived characters dozing at work and play. It was in 1758, according to the Oxford English Dictionary, that the word insomnia entered the English language.

What, asks Schmidt, did the new regime of caffeine, clocks, and clerics promote? Rationalism, work, productivity—and the decline of dreaming.