Today, during open awareness meditation, I found myself on the very edge of sleep several times. The task in this practice is simple: do nothing with your thoughts, just notice them come and go. A thought came, I saw it, it left. Then the next one.

Then something shifted. I seemed to be falling asleep, but I did not switch off. Awareness stayed, it just grew quieter. And in that quiet, images came instead of thoughts. Nothing special: the very stuff a dream would have been built from a minute later. As soon as I noticed an image, it dissolved. Just as a thought dissolves once it is noticed.

This happened several times in a row: thought, image, thought, image. And at some point I had a clear sense that thoughts and dreams are made of the same stuff. It is just that in one case I am awake, and in the other I am not.

After the meditation I wanted to check whether I had made this up. What do scientists and Tibetan practice say about it?

What science sees

This state has a name: hypnagogia, the passage from waking into sleep. Back in 1965, psychologists woke people at exactly this moment and found that the images at the edge of sleep are very much like real dreams, only shorter and simpler.

An interesting study came out in 2013. Kieran Fox, William Domhoff and their colleagues compared dreaming with mind wandering, the stream of thoughts that runs by itself when we are not busy with anything. The content is similar: mostly visual and emotional, the plot rough, with a touch of fantasy. And the same areas of the brain are at work.

Their conclusion: dreaming can be understood as intensified mind wandering. The main difference is that in sleep the parts of the cortex that let us see our own thoughts from the outside go quiet. That is why, in a dream, we do not know we are dreaming.

Here I recognised my own experience: the image dissolved exactly when the ability to notice came back.

What Buddhism says

Buddhist philosophers noticed this long ago and went further. In the 4th–5th century, Vasubandhu makes the dream his main example in the Twenty Verses. In a dream, things also have a definite place and time, just as convincingly as when we are awake. Only on waking do we understand that the mind made them. Hence his question: if the mind builds a world like this at night, what is it doing during the day?

In the Tibetan tradition a whole practice grew out of this: dream yoga. Tenzin Wangyal Rinpoche writes that our waking life is full of dreams too: fantasies, projections, thoughts. That is why the practice begins in the daytime, with a simple question to yourself: “Is this a dream?” The habit of recognising the dream by day carries over into the night, and back again.

Mingyur Rinpoche, my teacher, once advised making sleepiness itself the object of meditation: watch it roll in, and if it carries you off, wake up and watch again. He also said that one of his own teachers, Saljay Rinpoche, made this his main practice. So what happened to me is not necessarily a lost meditation.

The philosopher Evan Thompson brought science and practice together in his book Waking, Dreaming, Being (2014). He describes falling asleep almost like a contemplative: the sense of “I” loosens, images drift by, and the border between yourself and the world disappears. In his words, the “I” is not a fixed thing: it appears and disappears depending on how we are aware. And in meditation you can simply look at everything that arises and notice which parts of it we call “me”.

But not all drowsiness is clear

Here the tradition makes an important caveat. In shamatha there are two classic obstacles: agitation, when the mind scatters, and dullness, jingwa in Tibetan, when it sinks and grows dim. Thubten Chodron plainly calls images appearing as you fall asleep the coarsest sign of that dullness. So from the point of view of concentration, my experience was more of a slide than depth.

To my mind, both are true at once. If awareness dims along with everything else, it is just drowsiness, and you need to work with it. Dzogchen Ponlop Rinpoche suggests sitting up straighter, raising your gaze to the sky, splashing cold water on your face, going for a walk, or switching to analytical meditation. He admits honestly that it can be hard to tell a resting mind from one slipping into sleep. But if everything else grows dim while the one who notices stays clear, that is where dream yoga begins.

I think I had both. And this is a case where it is better not to decide on my own, but to tell my teacher.

What remains

Science and the tradition both seem to agree with what I felt: thoughts and dreams are of one nature. The only difference is whether the mind recognises its own creation.

So a thought is made of the same stuff as a dream. At night I believe the dream, and during the day I believe my thoughts in just the same way: a worry about the future, an old grievance, an argument in my head with someone who is not there. And in both cases one thing is enough: to notice.

This does not mean thoughts are useless. Like a wave, a thought does not exist on its own, and yet it can knock you off your feet. It is just that when you know what it is made of, you can use it rather than live inside it.

P.S. If you would like to try: tonight, once you are lying in bed, do not try to fall asleep and do not try to stay awake. Just watch how thoughts start turning into pictures. Most likely you will fall asleep before you notice anything. But if one day you catch that very moment of transition, ask yourself: where did the thought end and the dream begin?