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René Descartes was a philosopher, scientist and mathematician. Over the span of his 53-year life, he invented analytic geometry and came up with a theory of consciousness that inspired centuries of philosophical treatises.

Basically, Descartes crushed it — all the while spending 10 to 12 hours a day sleeping. His shut-eye schedule, just like his thinking, deviated considerably from the norm. Most people in 17th-century Europe rose by 5 a.m.; Descartes preferred to saunter out of bed around lunchtime.

In fact, as a new paper, Descartes and His Peculiar Sleep Pattern, published in the Journal of the History of Neuroscience, explains, snoozing not only occupied almost half of Descartes’ time, it also informed his philosophical and scientific work. Some even speculate it contributed to his early death.

A Practical Philosopher

In case you haven’t cracked open a Philosophy 101 book in awhile, the foundation and essence of Descartes’ logical philosophy is the simple phrase, “I think therefore I am.” As he saw it, to cast doubt on one’s very existence required thinking; and the act of thinking itself proved existence. Done and done.

But he couldn’t say the same of the material world — Descartes saw no way to know, for certain, that the world around him, or anything within it, was real. His formulation of this mind-body quandary became known as Cartesian dualism, a topic still worth at least five points on any modern philosophy final exam.

In hammering home his existence argument, Descartes made sure to discuss a variety of mental states. He held that people took breaks from mental awareness  — periods of suspended consciousness — in the form of nightly rest. During sleep, the mind couldn’t prove its existence. As Mia Woods explained, writing for Van Winkle’s:

[O]ur dream experiences — what we feel emotionally, or what we see, hear, taste, touch and smell — are, while we’re having them, as real as our waking experiences. We cannot rely on our senses to tell us the truth.

But that didn’t mean the sleeping mind didn’t exist. Even while asleep, the mind retained its “thinking” status (remember: thinking equals existence) because, according to Descartes, it stored the experiences perceived and digested by the waking mind.

In conceiving of the sleeping mind in this way, Descartes showed off his characteristic prescience. More than 350 years later, science is validating Descartes: The sleeping brain stores thoughts and solidifies memories collected during waking hours. In this way, they echo the Cartesian model of a mind-at-rest ceasing to absorb the outside world.

The Pineal System

Descartes regarded the material world with skepticism, but he was nonetheless a man of science. As such, he sought to place the mind somewhere in the brain, and settled on the pineal gland.

By some accounts, he picked the pineal gland because it’s not represented in both the right and left hemispheres. To Descarte, this suggested a greater unifying purpose. The small midbrain structure, he hypothesized, played a role in processing sight, transforming visual snapshots of the illusionary into real thoughts.

Today, the pineal gland is probably best known for secreting melatonin, the sleep-regulating hormone that responds to light exposure. Which brings us to Descartes’s extensive theorizing on  consciousness and sleep

As it turns out, sleep mattered a great deal to Descartes. From a young age, he rested more, and more bizarrely, than the average post-Renaissance Frenchman. He once wrote that sleep is “a time of nourishment for the brain.”

The Fragile Frenchman

According to his biographers, Descartes suffered from ambiguously “frail health” as a young student. While his hardier schoolmates rose at 5 a.m. to tackle chores and attend morning lectures, le fragile Descartes slept until lunch to conserve his energy.

He maintained the same schedule for most of his life: He dozed roughly from midnight until noon. Then he hung out in bed for a while, leisurely gathering steam to start his day after lunch. Upon moving to Holland, he gave the country props for letting him “sleep more quietly than anywhere else.”

There’s no evidence that Descartes considered his off-kilter sleeping schedule an issue, let alone a medical condition. But, in retrospect, scientists speculate that he had Delayed Sleep Phase (DSP), a circadian rhythm disorder marked by an abnormally late sleep-and-wake schedule. Otherwise, DSP sufferers sleep normally, just at different hours.

Lifestyle factors, such as nighttime light exposure (ahem, smartphones in bed) or simply going to bed later, can trigger DSP. But the condition also appears to occur naturally in some biologically predisposed night owls. And, while Descartes’ 12 a.m. bedtime may not register as unusual today, consider that his 17th-century contemporaries ordinarily retired at dusk, before the invention of street lamps enabled artificial illumination.

Did Disrupted Sleep Kill Descartes?

The DSP theory supports another posthumous postulation about the Frenchman’s relatively short life: That Descartes died at 53 because he had to start waking up early.

The year preceding his death, Descartes moved to Sweden to tutor Queen Christina, who insisted Descartes adopt her morning-lark ways. One early morning in February, just months after adjusting to the bossy royal’s early schedule, Descartes developed a fever. Within two weeks, he succumbed to pneumonia.

It’s possible that shifted sleeping patterns desynchronized Descartes’ biological clock, leading to chronic, damaging sleep deprivation. His immune system weakened, infection found its way into his lungs. Descartes and His Peculiar Sleep Pattern suggests that even limited sleep deprivation can affect immune response, resulting in lower levels of virus-fighting proteins. One animal study linked circadian-rhythm disruption to a four-times-higher mortality rate in response to sepsis.

The paper’s authors, based at the Clinic for Psychiatry and the Clinical Center of Serbia and University of Belgrade, Serbia, wrote, “If this were the case, it would be ironic that, at the end, it would be light acting on the pineal gland and his aberrant sleep needs that might have helped to kill him.’

Descartes’ sleeping habits place him among an assortment of other venerated characters known for loving late nights, including F. Scott Fitzgerald, Marcel Proust, Pablo Picasso and Jackson Pollock. Of this crew, just Picasso lived to see his 55th birthday. Maybe irregular sleep factored in, but we're betting the booze didn't help either.