Season 4 of The Good Place tackled this problem quite well.

Colour is not real and when you play a virtual piano on a VR headset, experience becomes real...

@user535733, and entire season is quite vague and a lot of investment of time. Can you please narrow it down to specific episode(s)?

Who wants to know?

reality check tag cannot be used alone. That apart, where is the worldvbulding problem here?

As @FranklinPezzutiDyer points out, the philosophical assumed by the question is called solipsism. The great defect of solipsism is that it is utterly useless -- yeah, one can never truly know for certain that there is more than one thinking entity; but there is nothing one can do based on this position. Anyway, metaphysis and epistemology are vaaaaast subjects, and completely off topic.

This looks far more appropriate for the philosophy stack than worldbuilding.

Ancient cultures made little distinction between dream and not a dream. However, try to be more systematic and structured break down your issue. If this is world building, perhaps start at the beginning. Maybe in your civilization, there is no difference. How does this work? I missed this place, this is the most tolerant and nicest thing on the internet. Only -1

This might be an interesting question I just don’t think by the metric that questions are judged this doesn’t seem to fit into this site. It seems kinda odd to me that this question remains as it is and open?

@L.Dutch - Reinstate Monica - I have added the philosophy tag. Worldbuilding is central to this. If the world is not real and is in my imagination then I have clearly built the whole world (including Stack Exchange).

@AlexP - "there is nothing one can do" - Clearly there is much I can do. In lucid dreaming, it is possible to do miraculous things like flying or even destroying mountains. If I am dreaming the world, I should in theory be able to change it any way I want.

"Clearly there is much I can do": obviously, there isn't. If "the life of the entire world if is a dream of the eternal night" (to quote a Romanian poet in my own bad translation) there is nothing outside the thinking subject, so that there is nothing to change, so that there is nothing to do. The thinking subject can think of destroying mountains, but he cannot actually destroy mountains because there are no mountains to destroy. No outside world means to morals, no ethics, no purpose.

Please re-read my question. "No outside world means no morals, no ethics, no purpose." Yes and that is the mindset of a psychopath. Such a person behaves as though they are the only person of importance. My actual question is, can we use logic or anything else to show that life is more than a dream?

No we cannot: Any discrepancy will be ignored, discounted, or twisted to support the original conjecture. Folks will believe what they want to believe it regardless of facts, evidence, or logic. See both the trial of Gallileo and conspiracy theories among many others. For an example of a real-life discrepancy that folks ignore or discount every day, see the Mpemba effect

That you have built a world in your mind doesn't make the question about worldbuilding, as much as asking "what is the past tense of to be on 747" is not a question about aviation.

@ L.Dutch - Reinstate Monica "That you have built a world in your mind doesn't make the question about worldbuilding", Um... The seems self-contradictory. Doesn't that describe every single valid question on this SE? Someone builds a world in their mind and then asks questions about it?

they ask questions to help in building the world. not questions about their world.

There has been debate on the topic of "everything is worldbuilding" from time to time. last I checked, the consensus was that a topic is worlbuilding if the poster thinks it is. However, from the wording of the question, I'd point out that this is far more focused on what has been done in real life philosophy, so it really is a better match there. You might be able to edit it to explain how answering the question will help you build a world. By bringing that into the puzzle, it may open more doors for world building style answers, rather than pure philosophy answers.

For example, it might open the door for a worldbuilding answer which shows that this question actually doesn't need to be answered to complete the particular world building task at hand.

Kiri-kin-tha's First Law of Metaphysics is "Nothing unreal exists." I'm really fond of that answer. 😁