Aristotle was a great one for counting stars, Plato for looking beyond them. If Plato said one thing about sleep, Aristotle was bound to say the opposite. It’s not that sleep was the biggest problem either of them encountered. But sleep is one of those issues in the history of philosophy, perhaps because it is so commonplace, which help bring basic attitudes into focus. People reveal a lot of themselves when they start talking about sleep and even more when they tell you why they can’t sleep.
Take Descartes and Hume, for example, often seen as sitting in opposite corners in the boxing ring of the history of philosophy. This may not be the kindest analogy: philosophers fight without gloves. The French René Descartes (1596–1650) was a man of profound doubts, which he expressed as certainties. The Scot David Hume (1711–1776) was a man of certainties, which he expressed as doubts.
Descartes didn’t like getting out of bed in the morning, seldom did so before midday and would, in the end, believe that the insistence of his patroness, the Queen of Sweden, to see him one morning at 5 am gave him the cold which cost him his life. Whenever Descartes did drag himself out of bed, he wondered if he was still asleep. His famous dictum, ‘I think therefore I am’, arose in answer to the conundrum, ‘How do I know that I am awake right now and not dreaming all this?’ His response was that famous use of the vertical pronoun: if there is an I in the driver’s seat, then you are awake and conscious. Descartes was using the notion of thought in a broad way. His position is not refuted by pointing to people who don’t think but still seem to exist.
Descartes was known as a rationalist because he thought philosophy began in the mind. Hume was an empiricist because he thought it began with experience, with things that can be empirically measured. His dictum was more ‘I am therefore I think’. The chubby Hume was one of the more affable people to overturn the Western mind: Immanuel Kant (1724–1804) said that reading Hume ‘interrupted my dogmatic slumber’. Hume’s astringent thought was at odds with his own pleasant character. Le bon David wanted people to be glad to know him. This was despite the fact that his radical scepticism led him to conclude that it was not really possible to know anyone. Or anything. Hume believed that just because the sun had risen millions of times before, there was no logical necessity for it to rise tomorrow. A thousand examples of a connection between two things could never be extrapolated to entail a causal connection between them. So, if Descartes got out of bed wondering if he was still in it, Hume got into bed each night with no philosophical conviction that he would ever get out of it. One day, he didn’t. He died in full possession of his doubts.
For Plato, doing philosophy was a bit like waking up well rested. Dawn is a key image in his work. One of his dialogues, Crito, deals with the impending execution of Plato’s mentor, Socrates. (The relationship between Socrates and Plato was, incidentally, anything but platonic.) This dialogue begins with the wealthy Crito visiting Socrates in prison at dawn. Crito says that he has been watching with envy while Socrates slept peacefully. Unlike Crito, who has been unable to sleep, Socrates is represented as a figure of order and moral calm. His integrity is reflected in unblemished sleep; his clear sightedness is evident at dawn. Similarly, in his final dialogue, The Laws, Plato portrays an ideal city called Magnesia, a name which implies greatness. Plato enjoyed toying with the concept of an ideal state. He was the first writer to describe the lost continent of Atlantis. In Laws, the supreme authority in Magnesia is a ‘council of the night’, a gathering of elders and philosophers that meets every day between first light and sunrise, the time when members would be most wide awake and least preoccupied by mundane affairs. Fresh from sleep, this group would discuss ideas. Plato’s idealism is evident in his belief that, if you jailed prisoners within earshot of this meeting, their behaviour would be corrected simply by hearing about The Right Thing To Do.
In Plato’s ideal world, philosophy is the work of dawn. He distrusted night. In his best known work, The Republic, Plato discusses sleep in the same breath as describing the ‘tyrannical character’ which forms part of an ‘imperfect society’. He says that sleep incapacitates ‘the reasonable and humane part of us’ and allows the ‘bestial’ part to do its worst. In other words, he is suspicious of dreams which lack both ‘sense and shame’. The answer is this: as you get near to sleep, discipline your mind and feed your reason with ‘intellectual argument and meditation’. These days, most sleep therapists would give precisely the opposite advice. They would also avoid attaching moral judgement to insomnia in the way Plato does, although they might concede that mental preparation for sleep can make a significant impact on the quality of sleep. But for Plato, there is no such thing as the sleep of reason. The body may rest. But the mind needs to be controlled until dawn. Indeed, the most famous image in The Republic is the image of the cave. Plato likens human existence to people living in a dark cavern, looking at shadows of animals and other figures. These shadows are but poor copies of real animals, the ideal forms at whose existence the shadows hint. We may in our lives get to know good people and from this begin to understand what goodness might be. But a good person is only a shadow of an ideal called ‘the good’. For Plato, true knowledge is of ideals such as ‘the good’. The journey of philosophy is from the cave into the first light of dawn.
For Aristotle, on the other hand, philosophy is not the work of dawn but of high noon. It needs the hard light of day. Like Plato, Aristotle had a lot to say about the way human beings should organise themselves into communities. Plato’s Laws begins with one person asking another whether or not God is the originator of laws. Aristotle’s best known work on the same subject, Politics, begins with the line: ‘Our own observation tells us that every state is an association of persons formed with a view to some good purpose.’ In other words, Aristotle starts with observation, with experience. Plato starts in the abstract, in the realm of the ideal. One looks at his feet, the other beyond the far horizon.
The result with Aristotle is a colourful melange of sense and nonsense. In his treatise On Dreams, he says that the surface of a mirror will always appear red to a woman when she is having her period. This is because her eyes are full of blood at that time. But in the same breath, he suggests evocatively that dreams are caused because the mind in a human body is a bit like a passenger in a vehicle. The mind still keeps moving for a time after the body in which it is travelling has stopped. It has a momentum of its own.
Aristotle’s small treatise On Sleep and Sleeplessness is likewise so wide-eyed that it is sometimes blind. And yet it also has moments of genuine understanding. It goes into elaborate detail about humours evaporating from food in the stomach, rising through the body because they are hot and entering the brain, having a narcotic effect. This is the philosopher’s way of saying that everyone falls asleep after a good lunch. The sleeper nods. Their eyelids feel like a dead weight. They can’t stand any more. Aristotle says this is because the humours entering the head have made the head heavier. People wake when digestion is complete and the heat flows out of the head back down to the body. Thus when they wake, people find their heads are lighter and they can hold them up. He notes that babies sleep a lot because they have large heads in proportion to their bodies. He also says that the bigger a head the more likely someone is to sleep. ‘Dwarfish or big-headed types are addicted to sleep.’ Strange to say, modern medicine will find more than a grain of truth in all this, as we will discover later in the night. It will also find truth in his contention that sleep is something peculiar to creatures with hearts and, therefore, with blood. Aristotle notes that melancholics are hard to accommodate in his scheme because they eat a lot but don’t sleep much.
But it is the opening and close of Aristotle’s treatise which contains its most tantalising wisdom. Aristotle concludes by saying that we sleep simply because it is in our nature to do so and that no animal can live in defiance of its inherent nature. He leaves up in the air the famous question from which he set out: sleep could be an activity of the body or the soul or both. For once, he doesn’t have an opinion.