Cognitive Sciences Stack Exchange is a question and answer site for practitioners, researchers, and students in cognitive science, psychology, neuroscience, and psychiatry. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

As he saw; he could see a packed court and his ministers coming up to him for advice and then he felt his eyelids shutting down...We he opened them he found sitting at a street corner asking for alms.

Is he a king dreaming that he has become a beggar or the other way round.. Is there any experiment which can clear his dilemma.?

Of course this relates to the "Brain in a vat" topic : wherein my question would be "Am I what I see or just a brain in a vat ( akin to the movie "Matrix") : how do I find this out"

share|improve this question
Watch the movie "Inception." Fictitious anecdotes ftw. – Taal Sep 27 '13 at 15:38
Could you amplify – ARi Sep 27 '13 at 15:45
Kind of hard to explain now that I think about it - it involves using something like a "top" - in their dreams the top would never fall over - or they would at least know in real life how long it should take to fall over. In reality it always does....I know that's a horrible explanation. You can try reading or watching the movie though - it would help more. It's an awesome movie anyway. – Taal Sep 27 '13 at 16:13
That helps.. Though the top may fall over in dream too. – ARi Sep 27 '13 at 16:18
Hi, special theory of relativity might offer for you such a test. That is when you go with hispeeds and space travel then you will see everyones gone and you will observe a different civilization when you come back to earth. And that all is due to time dilation. – Waqar Ahmad Oct 5 '13 at 11:29

I don't think a "reality check" kind of test will work.

Whatever aspect of your waking reality you take for granted, you'll never know if maybe your waking reality has changed. Maybe someone has invented something you didn't know about (an implant that allows people to breathe under water); maybe God has changed the physical laws; maybe magic does exist. Who knows. You simply cannot be certain. We don't yet understand our reality enough to make 100% predictions. Basically, anything at all is possible, however unlikely it may seem to us at the moment. People a few hundred years ago would see much of what we take for granted today as magic.

But I don't think you need a logcial test. Because the difference between a dream and being awake is not how the respective reality works, but that you yourself are in a different physiological and psychological state. In everyday life you are never mistaken about when you are awake. You may experience certain moments during a dream, usually shortly before you come awake, when you are not sure if you are dreaming or not. But as you slowly wake up and your waking mind begins to consider the dream that your dreaming mind is immersed in, you easily notice that the ringing is your alarm clock and you are not naked in a bar, that is you understand which perceptions are part of the dream, and which are real and come from outside of you. When you are really awake, it simply feels like being awake. Your perceptions are different, your mind works different, and you yourself feel different and know that you no longer sleep.

So I would say, the test is quite simple:

When you wonder if you are dreaming or awake – you are dreaming.

This, of course, goes for a healthy mind. Drugs, mental disorders, and stress, can change your perceptions.

share|improve this answer
This is an excerpt from an ancient Sanskrit text Tripura rahasya (138-144). "The difference between dreams and the wakeful state lies in the fact that in the waking state the dream is determined to be false, whereas in the dream the waking state is not so determined. Therefore the waking state is universally taken to be real. But this is wrong. For do you not experience the same extent of permanency and purposefulness in dreams as in the wakeful state?" – ARi Sep 27 '13 at 19:05
No, you don't. In the dream, you do not know of the other state. You exist totally in your dream. Only when your waking consciousness awakes while you are still asleep – either shortly before awakening or during lucid dreaming – can you consider the reality of your current experiences. Your dreaming subconscious is unaware of waking reality and unable to conceive of it. It does not wonder if you dream. It lives in the dream. Permanently. Even when "you" are awake, it isn't. So the fact that you can think of both states, but are still in the physiological state of dreaming, that is the clue. – what Sep 27 '13 at 19:44
Hypothetically; with regards to what you say ... if you consider a dream within a dream.. does the issue still remain the same? – ARi Sep 27 '13 at 19:46
I have never had a dream within a dream. – what Sep 27 '13 at 20:42
dreamsception ? , wow, dat's fresh – Enoque Duarte Oct 2 '13 at 11:00

Reality Checks may do what you request, if we stick to certain assumptions:

  1. We are already considering whether we're in a dream or not.

  2. The sleeping world cannot be as detailed as the waking world.

  3. We cannot be convinced by the dream world of things that contradict what we observe.

In this our possible dream world, we locate a clock. We make note of the clock's time. We go about our business. We note our clock's time again and compare whether the two time differences are sensible for the events. Repeat. Track days, weeks, months, and years if necessary. On assumption 2, the dream should fail to be detailed enough to consistently count time. If it isn't, it should fail to properly account for time, events won't start and stop, people won't age, and/or you won't die. Assumption 3 means we won't accept some sort of paradox solving rewrite of observed events, such as the time changing as soon as we realize the inconsistency.

Similarly, we could measure space and make sure that the size and distance of objects is consistent.

More extremely we could kill or injure someone, maim ourselves, or even kill ourselves. Any of these actions would demand consistency (that person is dead/injured, we are in jail, we are injured, we are dead) and killing yourself would also demand the dream to end to ensure consistency.

share|improve this answer
Whatever criteria (reality checks) we may have for discriminating reality it can be dreamt of being confirmed to in dream. Killing one self is not guaranteed to provide an answer and may fail nearly half the times. – ARi Jul 4 '15 at 9:32

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.