Dreams, memories, the sacred–they are all alike in that they are beyond our grasp. Once we are even marginally separated from what we can touch, the object is sanctified; it acquires the beauty of the unattainable, the quality of the miraculous. Everything, really, has this quality of sacredness, but we can desecrate it at a touch. How strange man is! His touch defiles and yet he contains the source of miracles.

Part of the explanation for why dreams can be so weird is that they are interpreted from chaotic information. The evolutionarily older parts of our brain are also the seat of our basic emotions. According to this theory, the emotion comes first, and dreams are made to make sense of that emotion. Evidence for this position comes from scene changes that happen: when we have anxiety dreams, for example, they often switch from one anxious situation to a different one—so rather than us feeling anxious because of the content of our dream, it could be that our feeling is causing an anxious narrative in the dream!

Why humans dream remains one of behavioral science’s great unanswered questions. Dreams have a purpose but it may not be to send us messages about self-improvement or the future, as many believe. Instead, many researchers now believe that dreaming mediates memory consolidation and mood regulation, a process a little like overnight therapy. But it’s not a benefit all share equally: People who are sleep deprived also tend to be dream deprived, spending less time dreaming and perhaps not remembering dreams as well.

If dreams were movies, they wouldn’t make a dime. They’re often banal, frequently fleeting and they’re screened for an audience of just one. As for the storyline? You’re in a supermarket, only it’s also Yankee Stadium, shopping with your second-grade teacher until she turns into Ruth Bader Ginsburg. Then you both shoot a bear in the cereal aisle. Somebody call rewrite. But dreams are vastly more complex than that, and if you’ve got a theory that explains them, have at it. The ancient Egyptians thought of dreams as simply a different form of seeing, with trained dreamers serving as seers to help plan battles and make state decisions. The ancient Greeks and Romans believed that dreams were equal parts predictions of future events and visitations by the dead.

A dream is a succession of images, ideas, emotions, and sensations that usually occur involuntarily in the mind during certain stages of sleep. The content and purpose of dreams are not fully understood, although they have been a topic of scientific, philosophical and religious interest throughout recorded history.