by Brian Tomasik
First written: 6 Jul. 2016; last update: 5 Dec. 2016


This page recounts three different occasions in which, during dreaming, I've been convinced that I wasn't dreaming because everything seemed so real to me. This has implications for arguments that dismiss skepticism or simulation hypotheses based on how real things seem to us.


"But [my dream] was so real!" she said, calming down a bit.
"That's how it is with dreams," he said. "It's as if they're really happening, but they're not -- they're just in your mind."

--The Berenstain Bears and the Bad Dream


Samuel Johnson famously tried to disprove Bishop Berkeley's idealism by kicking a stone and saying "I refute it thus." Similarly, G. E. Moore attempted to refute skepticism about the existence of the external world by noting that he had two hands that seemed to actually exist.

Similar sentiments sometimes appear in response to the simulation hypothesis or other weird ideas.

An interesting test for the reliability of these intuitions is the case of dreams. The following sections describe three dreams I've had in which I've been convinced that I wasn't dreaming, only to discover that I was.

In "The Simulation Argument FAQ", Nick Bostrom says:

Consider the fact that while you are dreaming, your own brain often succeeds in making you unaware of the fact that you are dreaming. If your own humble brain can do this, then presumably it would be quite feasible for some technologically super-advanced builders of ancestor-simulations to achieve the same delusion.

Dream from 2 Nov. 2013

One time I was with my friend, riding in the car on the way to the house of someone who lived nearby. On the way, we saw hay bales lying in a field, waiting to be harvested, and my friend said something to the effect that "People who harvest hay don't like their jobs."

We pulled into the driveway of the house, and as I got out of the car, I noticed a wood-carved sign in which each letter was hollowed out, and the letters were connected enough for the sign to hold together. The sign said something like, "People who harvest hay do like their jobs."

I was amazed. How was it that there was a sign that exactly countered a throwaway comment my friend had made in the car ten minutes ago? No one could have constructed the sign that quickly, nor could the people we were visiting have heard my friend make her comment. Yet I'd never heard of this as being "a thing" that people talk about and make signs about. Could they have convergently thought about the same idea? That seemed far-fetched.

I got out of the car, hopped onto the porch, and paced around (as always, scanning the floor to make sure I wasn't stepping on bugs). I pondered about what I had seen as I waited for the others in the car to get ready. I had the following inner dialogue with myself:

Me1: That was really weird. How could that have happened?
Me2: Maybe I'm in a dream. That could explain seemingly supernatural events.
Me1: Nah, can't be. I can feel that this is real life. Dreams are more fuzzy. Take this porch. Isn't the wood here totally solid?
Me2: Yes, it does feel solid. Still, it could be a really lifelike dream. At least you should raise your Bayesian posterior odds for that.
Me1: Hmm, fine. But I still doubt it.

I continued walking on the porch, trying to stay away from a wasp that was also occupying it. Then I saw that the others were also out of the car and ready to go ahead.

...And then I woke up. Indeed it had been a dream, just as my logical reasoning while dreaming had suggested.

Dream from 10 Dec. 2014

I was in motion, in the back of a truck that no one was driving. It crashed -- that was stupid.

It got dark. I went to my house and left the truck behind. I wondered how I could have been so stupid. I said it was as if I was dreaming? Oh well; I was stuck with my stupidity. Darn.

I couldn't believe it. I couldn't imagine that it had actually happened.... And then I woke up.

Dream from 27 Jun. 2016

I was wistful about an old friend. I was sitting on a bench in a house. Then my old friend actually showed up, and we sat together, talking.

I joked that I sometimes have dreams about meeting old friends, and then I wake up and discover they weren't real. This was a sarcastic comment, since I was sure that this occasion actually was real. We talked some more about old times.

...Then I woke up.

Related dreams

4 Dec. 2016

I was in a series of rooms somewhere. Someone told me that there was a book that predicted my birth name a few days before I was born. "Hm," I thought. "That's interesting, but maybe my parents just decided my name ahead of time and told the book author? It's not enough evidence to warrant supernatural conclusions."

Other incidents similar to that happened as well. I began to suspect that I might be dreaming, but I wasn't sure. I wondered to myself whether there was a way I could test that I was dreaming. I thought: "Maybe I could do a complex calculation -- one that would be too difficult to complete successfully in one's sleep. But how would I verify the answer? I might just dream that I got the correct answer, even though I didn't."

I spent another minute or two trying to devise ways to test whether I was dreaming.

Then I saw my mom. When she smiled, her lips unveiled a set of orange teeth. "Aha," I thought to myself. "This must be a dream after all." I tried to wake up to get out of the dream, and I successfully did so.