I'm not asking whether other minds are real or not, I'm asking whether the whole shebang is "real".

Google Gemini says it's impossible to know/prove it, and basically says to "move on". The only sort of explanation it's given is that the outside world is "consistent" and "predictable" (by using science) but hallucinations can be consistent too.

For all I know I can be a computer program and even my entire body is not real. How do I prove the world is real, and I'm not just hallucinating everything?

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    – Philip Klöcking
    Commented Apr 1 at 7:00
  • What is real, to you? If your sensory inputs are not a solid definition of real then you have some work ahead of you that is unlikely to lead anywhere.
    – Stian
    Commented Apr 1 at 9:08

6 Answers 6


It sounds like you're asking:

How do I know reality is real?

So, there are variety of scenarios that have been offered in philosophy that challenge the thinker to think about proof and reality. All of them center around how do you prove reality is real:

This is a good introduction into some key philosophical terms that stem from asking some simple-sounding questions:

  1. What is reality?
  2. How do I know what is real?
  3. How do I prove something is real?
  4. What is evidence?

These are the sorts of questions that start one down the path of reading more complex philosophy! Let's just craft a simple response. By knowing the four definitions above and then being acquainted with some key ides, you can begin to answer the question for yourself.


The study of reality and its substituents is called ontology. The starting position of many thinkers about how build up the picture of reality and figuring out which things are part of it is that of naive realism. As a thinker becomes more sophisticated they might find other models such as scientific realism or subjective idealism, and so on. In the West, educated society has largely moved towards philosophies that are grounded in naturalism and physicalism in the secular world though Christian theology is still a fundamentally powerful source of philosophical thinking. Modern Catholicism offers a good blend of both.


How do you know something is real? How do you know anything and what is knowledge? The classical tradition going back to the Socratics is that of justified, true belief. There are some technical problems arising from Gettier problems. Then there are sources. Robert Audi, for instance, offers consciousness, reason, testimony, perception, and memory. The technical language about deciding whether something exists has to do with terms like existential quantification and quantifier variance, but those tend to be ontological terms where as the actual justification or judgement (SEP) is rooted in philosophy in terms of argumentation theory.

Proof and Evidence

These two terms are highly interlinked. A proof is a method that uses evidence to justify a conclusion. This requires a theory of evidentialism. This will vary from thinker to thinker. For instance, it is quite typical for theologians to accept supernaturalism and the power of faith. Revelation features quite prominently in terms of evidence among some traditions. In the secular world, empirical evidence and rationality figure quite prominently in proof. A good place to start for informal reasoning is Toulmin's Uses of Argument for his method. Argument maps are another tool for organizing proof and evidence.

The Non-Answer to Your Question

What you accept as proof that reality is real will be up to you. There is no authority that can tell you what is right and wrong, though some ideas and techniques are more useful than others. That means you'll have to read through these sorts of materials and come to a decision about what you personally favor. Personally, I would appeal to James Halliday aka Anorak the All-Knowing:

And that was when I realized that... as terrifying and painful as reality can be, it's also... the only place that... you can get a decent meal. Because, reality... is real.


Two options: this reality is really real, or it isn't.

If reality isn't real, you're probably not going to be able to prove it's not real any time soon, nor figure out the real nature of reality. You're stuck here, in this fake reality, and so the stuff you do here will have the consequences it would have as if it were real even if it isn't. If you cut off your hand, it hurts and you have no hand. If you jump off a building, you break your legs - it really hurts, and it's expensive, and the recovery time is long.

If reality is real, then... all the same stuff above applies. You've got consequences that you have to live with.

The best option, I think, is to not worry about certainty, live your life as if it were real, because the consequences for messing up suck either way, but allow yourself a tiny little corner of your brain to acknowledge, every now and then, the tiny probability that it's all fake.

  • I really like your answer but honestly what really matters is does it matter if life is real or not? Is it good if it is real, is it bad if it is real? I mean as long as you are living and there is experience isn't that what matters.
    – How why e
    Commented Mar 29 at 17:06
  • 1
    @Howwhye it might matter a little bit. If someone is convinced life isn't real, and thus can justify torturing other humans because they aren't really there, then it matters a whole lot if they're wrong. Right?
    – TKoL
    Commented Mar 29 at 17:09
  • I guess so, valid.
    – How why e
    Commented Mar 29 at 17:26
  • I walk in a nearby cemetery often.
    – Scott Rowe
    Commented Mar 30 at 23:35

There can be no such proof, but allow me to make a very simple argument against it by asking the following question.

Suppose we are hallucinating this. If we are, then this assumes there must be a reality outside of this hallucination (for otherwise the concept of a hallucination doesn’t make sense). Now, would that reality also be a hallucination? And if so, would the reality outside of that hallucination also be a hallucination?

As you can see, one can keep doing this forever. But something, somewhere, must be real and not a hallucination. The most parsimonious answer is to assume that this reality is the one that’s real and that there is nothing else.

  • 1
    How do you know that a hallunication requires an outside reality? ;) What reliable reasoning source are you citing to evidence that? How do you know that source to be reliable?
    – Brondahl
    Commented Mar 31 at 0:04
  • If our Universe did not exist, would we notice?
    – Florian F
    Commented Apr 2 at 17:06

The only tangible proof of a hallucination would be technical recreation of a similar quality believable hallucination. In a couple of hundreds of years, people should have sufficient computing power to simulate all the electrical signals the human brain receives and create 'hallucinations' indistinguishable from our reality.

That would be reasonable proof that our World is most likely a computer simulator.

  • So we would be simulating our simulated reality inside a simulator? I'm not thinking that the world is a house because I live in a house... (If you say the word 'house' over and over, it begins to sound really strange and artificial.)
    – Scott Rowe
    Commented Mar 30 at 23:40
  • @ScottRowe - Science is trying to simulate and test everything on Earth. It is just natural that at some point they will try to simulate the Heavens. Commented Mar 31 at 0:07
  • Right, but no one gets wet in a simulated hurricane. The word 'hurricane' comes from the Mayan word for whale.
    – Scott Rowe
    Commented Mar 31 at 12:03
  • This is not a good argument. We can create synthetic diamonds that are indistinguishable from natural diamonds. Is this proof that natural diamonds were actually created in some lab and placed, Strata-style, to confound people? We can take hydrogen and oxygen, mix them together, and create "artificial water," completely indistinguishable atomically from the water we see in nature. Does this prove that someone must have engineered all the water we see in nature?
    – Obie 2.0
    Commented Apr 1 at 6:19
  • Or, phrased another way: isn't this basically just the creationist argument from design—unconvincing to anyone who believes in biological evolution—lightly adapted to an atheistic context? Call your hypothetical simulator "God" and the two become effectively identical.
    – Obie 2.0
    Commented Apr 1 at 6:24

The question can answer itself depending on the definitions used.

Do you think there are fundamental differences between perceiving reality vs. hallucinating?

If so, do you think those differences are knowable? Are they accessible, to the perceiver?

If, by definition, there is no difference, or, there is a difference, but it is unknowable, then it follows that there would be no way to distinguish reality from hallucination.

If, by definition, there is some collection of properties distinguishing hallucination from real experience, and that difference is knowable, then one would need to check if their own experience did or did not meet those criteria.

In my opinion, this question can be investigated in a very logical way, in the sense that, it can proceed by necessary tautologies, without requiring any empirical knowledge.


It can't be proved that life is real since we don't know what is beyond death! I meant, what if we are just computers and know that only after our death? What if this life is only a dream and when we die, we are welcomed into reality?

  • I really appreciate your contribution and am just suggesting that if you could expand on your thoughts it would be great. Thanks. Commented Apr 3 at 13:17
  • I am saying there is no line drawn between reality and illusions. For instance, take dreams as an example. What if this world is just a dream and death is the awakening or the ultimate truth but we don't know much about death so we can't make any comments. Commented Apr 3 at 14:58

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