Presumably, you’re reading this while you’re awake. How certain are you that you’re awake? And how much of a sliver of doubt should you have that you’re possibly dreaming? If we think in terms of credences (I do not personally approve of the idea of credences but nevertheless), what percentage would you attach to the possibility that you’re dreaming? 0.01%? 0.0001%? 0%?

Intuitively, it seems that if I have no reason to doubt I’m awake, I should be certain that I’m not awake. One can argue that I cannot prove that I’m not dreaming for sure. But proof is based on reasons which themselves seem subjective, and to me, having the experience of feeling awake is enough reason to give me certainty that I am. In fact, I would bet any amount of money that I am. What about you?

EDIT: this is not a “How do I know I’m not dreaming?” question. This is a deeper question of what credences you should attach to certain things

  • 2
    It's difficult to pick the best reason for closing this question. Likely a duplicate, likely not about philosophy, likely opinion-based.
    – tkruse
    Commented Jun 21, 2023 at 8:07
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    We are not certain, fullstop. Commented Jun 21, 2023 at 8:09
  • Does certainity even apply to such questions? You can be prepared for multiple different outcomes.
    – rus9384
    Commented Jun 21, 2023 at 8:18
  • Sometimes when I am asleep I realize I am asleep, but I never have the thought that I am awake when I am asleep. If I have the thought that I am awake, it is proof that I am awake.
    – Scott Rowe
    Commented Jun 21, 2023 at 10:10
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    Does this answer your question? How does one know one is not dreaming?
    – NotThatGuy
    Commented Jun 21, 2023 at 12:22

4 Answers 4


Dreams seem to be a "simulation" of reality, where the brain predicts or reiterates scenarios that have or could happen. However as a consequence of the complexity of reality the brain is ill-equipped to handle reality in it's entirety. Though as you are only ever aware of your focus of attention, it's sufficient for your brain to render that part of reality, so that things "feel" real even if they aren't.

Though as a consequence apparently object permanence is something that is not a given in dreams, so there are accounts of people looking at clocks (those with hands) and have them move erratically as objects seem to be generated when you think of them instead of persisting and evolving even if you don't think about them.

So there are people who claim to be able to achieve lucid dreaming, where you are able to achieve awareness of being in a dream. Which then is supposed to give you control of the situation and to simulate actively rather than passively. (How much that ends up messing with your perception in the real world I don't know).

But technically it might be able to tell if you are dreaming by pushing the boundaries of what is possible in dreams which is not possible in reality and so on.

Though ultimately that would have just proven a different state of perceived reality, while "reality" might still just be a dream. If you only ever dreamed, reality might be the real illusion, where things don't happen as "normal". So you would need to define what "awake" even means.

And is it a state of ourselves or is it a state of society. Like sleep could also be defined if people around you seem to pass out and become unresponsive without obvious harm. And as we see others do it, we assume we're doing it ourselves as well.

Though if you're would not be able to tell dream from reality, is it really useful to apply credence other than "assume you are always awake, because if you are you better be and if you aren't you still kinda need to to make this simulation work?"

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    Please stay away from cars. :-)
    – Scott Rowe
    Commented Jun 22, 2023 at 2:11

Here's the bad news. The big difficulty with any attempt to reach 100% certainty right now is that it can turn up in your dreams. So if you think you're feeling that you are awake is a guarantee, or even evidence, that you are not dreaming, I'm afraid you are on the wrong track.

There is a real possibility that you will wake up one morning and realize that while you were asleep, you dreamt that you were awake. In fact, if you dream you are having any experience, you are already dreaming that you are awake. You may not have noticed that, but only because your dream did not lead you to ask the question. But it could - or at least you cannot guarantee that it couldn't.

(The puzzling possibility is that one might dream that one is dreaming - would that be a dream within a dream? H'm. I've never heard of that, so I shall worry about it when it happens.)

Is that just a logical possibility? It certainly is that. But I was once told by a friend that he had learnt to tell whether he was dreaming or not. Sadly, he never told me what it was. Why? Next time I saw him, he told me he had dreamt it.

Here's the good news. You can tell for sure when you have been dreaming. You were taught how to do that at a very young age when you woke up distressed in the middle of the night and woke up everyone else. They taught you that you had dreamt about leaping over tall buildings to escape from the wolves. For once, the adults in your life were right.

I suggest that the problem with the question "Are you sure you are dreaming right now" is the "right now". The answer is, No. But you can tell in retrospect.

If personal experience may be allowed to intrude, there are one or two incidents in my life that I thought were real for years. Eventually I worked out that they could not possibly have been real. Time will tell.

Incidentally, a dream within a dream would only count if the dreamer dreamt about waking up and realizing that the previous dream was a dream and then wakes up and realizes that the whole thing was a dream.

  • +1 for dream within dream, which fundamentally changes the gravity of the question but is little point talking to those who've not experienced it
    – Rushi
    Commented Jun 21, 2023 at 14:23
  • Thanks. I appreciate it. I wouldn't dream of pursuing that speculation further until there's a reliable report of it happening. As it happens, I'm actually quite sceptical about dream reports. After all, we dream impossible things all the time (our imagination just skates over the details. I'm not even convinced about lucid dreaming, and there are certainly reports of that.
    – Ludwig V
    Commented Jun 21, 2023 at 16:28
  • I am 100% certain that I am awake right now. For you to say that it’s possible that I am not awake right now requires evidence. You don’t have any. One can conjure up any number of possibilities. So you have no basis by which to say I’m on the wrong track
    – user62907
    Commented Jun 21, 2023 at 17:26
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    You reject the idea that you might be dreaming right now on the grounds of lack of evidence. You are right, of course. But dream experiences are indistinguishable from waking experiences - until the dreamer has learnt the difference. Without that learning, they believe that their experiences are real. They can only learn to tell the difference when they have woken up. Consider hallucinations like Macbeth's. He is awake and not dreaming. He cannot tell that he is hallucinating while he is hallucinating. That's the nature of the phenomenon. Why would dreams be any different.
    – Ludwig V
    Commented Jun 21, 2023 at 18:00
  • Because there’s many experiential elements to wakefulness that is missing in dreams
    – user62907
    Commented Jun 22, 2023 at 6:01

In my case (I have severe tinnitus) my ears ring continuously whenever I am awake, and in my dreams I do not have any ringing. So as my tinnitus fades out I know I am entering the dream world.

  • Beautiful. Yes, I often perceive the drop off of background sounds as I fall asleep.
    – Scott Rowe
    Commented Jun 22, 2023 at 2:04

If you can read, write, and do arithmetic, you're almost certainly not dreaming. Relevant paper via Google Scholar.

  • Finally, an explanation why we are not allowed to sleep during work or school! To say nothing of driving... Why does the car always go backwards when I'm dreaming?
    – Scott Rowe
    Commented Jun 22, 2023 at 2:06