Freud, apparently, thought dreams prevented us from going crazy. According to him, dreams are expressions of the desires and fears we don’t dare face in waking life, facets of ourselves that we repress like a child smothers a ball under the surface of a pool. And, in the dark of night, dreams relieve the pressure by playing out these urges. Were they not allowed these covert outings, but blocked and pushed indefinitely, they would eventually burst through the surface and rupture our psyche. And so dreams are the release valve for the unrelenting force our unconscious exerts to have its will expressed.

This idea intrigued a young William Dement and launched him into a trailblazing career in sleep science. Could he use science to prove Freud’s theory right? REM sleep, which Dement discovered, seemed promising. Studies proved it to be both indispensable and the only part of sleep when dreaming occurred.

And there was the case of a radio personality suffering a mental breakdown during his 201-hour “wakeathon”, in which he broadcasted, without sleep, for a week straight. Why did he start hallucinating and dissociating? Was it just the drugs he took to stay awake, or could it have been the absence of dreams, which would have helped keep his psyche in balance? Dr. Dement’s faith in Freud’s theory finally faltered after accompanying a high school senior’s record-breaking sleepless marathon of eleven days and witnessing nothing much worse than acute fatigue and acute crankiness.

Some scientists have claimed the opposite to Freud’s theory – that dreams not only do nothing but mean nothing. They are a random side-effect of the brain function that produces them, a periodic electric signal that occurs right before and during REM sleep. Our eyes move rapidly and we experience absurd scenarios because electricity is coursing through our neural network like water splashing over rocks. But, as Dement points out, even if the ripples of electricity start out with no intended destination, their traversal is influenced by pathways carved out by our thoughts and behaviors. In the same way that water trickling down the face of a rock follows paths determined by the rock’s shape and texture, our dreams depend on the paths our neurons allow electrical signals to traverse. The meaning of a dream comes from our neural connections, which we wired and rewired continuously throughout our life.

Dreams have things to tell us, whether or not all scientists agree. It is an ordinary thing to dream about things that came up during the day. In his essay The Kekulé Problem, Cormac McCarthy considers the curious phenomenon of problem-solving while sleeping, with particular interest on why solutions are presented mysteriously as images and not in plain language. He offers a clever answer: the brain is old, but language is new. And, just like we prefer to communicate in our native tongue, our brain prefers to express itself through imagery.

But this idea, stirring as it is, might be no more accurate than Freud’s. In his book Livewired, neuroscientist David Eagleman proposes a theory of dreams that suggests a rather different answer to the Kekulé Problem. He proposes that the brain activity responsible for dreams, which targets the parts of the brain typically used for vision, exists to maintain our sense of sight. Without this scheduled strengthening exercise, it could be overtaken by other, neuron-hungry brain processes that don’t depend on light of day to stay active. If this is true, then the answer to the Kekulé Problem is less mysterious. Dreams are visual because their machinery is.