Obviously I'm not looking for a valid deductive proof using formal logic, but at least a relatively convincing argument.

How do I know that humans who I encounter other than myself have sentient minds, and aren't just unfeeling zombies?

It seems unreasonable to use the induction: "I am, in all observable ways, a human, and this human (me) is conscious, so all humans are conscious" or any from of that argument (such as, 'I know of this thing (me) that speaks about consciousness is conscious...) because I only know for certain of one such instance, and I'd never want to make a general induction from just one instance. (Imagine: "this person is a blue-eyed carpenter, so all people must be blue-eyed carpenters")

Is the fact that, from my own perspective, people act and speak as if they have conscious minds, enough for me to conclude that they are indeed conscious? Would it be unreasonable to conclude the opposite, that nobody posses a conscious mind besides for myself?

The only reason why I might be inclined to believe that other people have conscious minds is that I have a hard time believing in zombies, but if philosophical zombies are possible, than it seems more reasonable to conclude that other people are in fact zombies instead of attributing to them the added complexity of a conscious mind. Does anyone discuss the idea that belief in zombies might negate the belief in others' minds?

Related zombie questions: their existence, cognitive ability, and other implications. (There's no 'zombie' tag yet)

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    @user4894 see the first sentence of the question
    – That Guy
    Commented Aug 11, 2014 at 5:38
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    Do you have a reasonable basis for believing that you are not a zombie? Why can't you have mistaken zombie existence for sentience? That zombies aren't very bright is a corollary of your premises, after all. In the end, this concern reduces to all people are not people. QED all people are not zombies and language can be abused. Commented Aug 11, 2014 at 6:12
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    @paulross I am firmly opposed to discrimination against zombies in all its forms. Where do you think Peter Singer would come down on this? Commented Aug 11, 2014 at 11:47
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    @user3293056 it's irrational to make an induction based on only one instance
    – That Guy
    Commented Aug 12, 2014 at 22:16
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    If you tell the zombies that you are the only one with a sentient mind, and you are not, they will take you and put you in a padded cell. They will do that whether they are zombies or sentient, because those zombies behave in a way that is indistinguishable from sentient beings.
    – gnasher729
    Commented Jan 17 at 22:52

17 Answers 17


It is more complex and convoluted to explain why other human beings would present such an utterly convincing simulation of consciousness and sentience than to simply assume that they are conscious and sentient (you haven't eliminated the complexity, just displaced it).

  • How is your answer different than @Dave's?
    – That Guy
    Commented Aug 11, 2014 at 15:01
  • My answer is intended to directly address your statement if philosophical zombies are possible, than it seems more reasonable to conclude that other people are in fact zombies instead of attributing to them the added complexity of a conscious mind. Your reasoning is that a zombie is simpler than a being with a conscious mind, and therefore more plausible, but my answer points out that you're only displacing the complexity, you aren't eliminating it. (@Dave's answer is richer and more fully elaborated, but it also has more dependencies.) Commented Aug 11, 2014 at 15:30
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    For my part, I appreciate this answer's succinctness.
    – Dave
    Commented Aug 11, 2014 at 19:33
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    So believing that other people also have minds is very reasonable and rational?
    – Johnny5454
    Commented Oct 28, 2022 at 13:08
  • What type of reasoning is this? Is it abduction?
    – Arnold
    Commented Apr 16 at 18:45

Asserting that "I have conscousness but no one else does" has a degree of implausibility similar to that of geocentrism: why, out of all of the (more or less) externally similar human beings does this one (me) have consciousness (i.e. a special place in the universe)?

Basically it's an assumption of uniformity of properties across the class of objects we call humans -- which is a more simple hypothesis that is consistent with all of our observations than the hypothesis that only one (or a small fraction) of humans are conscious. This can be seen as an empirical, scientific proof that (essentially) all humans are conscious.

In common usage, we can tell the difference between someone who is conscious and one who is not by whether they respond to stimuli, move around etc. Note that there are also what I would term as reduced forms of consciousness, e.g. people undergoing a stroke who are not fully aware of their surroundings or able to form memories etc. The main point is that we infer that their mental state is different from normal (or ours) because the resulting behaviour is so different. Different outcomes due to different causes. Conversely, as we interact with unimpared people, we see behaviours that are at least plausible given our mental states, and use the principle that similar outcomes came from similar underlying mental processes.

It's this assumption of uniformity, similar outcomes from similar causes, that is the logical weak point in this argument. However, it is not an unacceptable position in scientific thinking as long as there is no other evidence against it.

  • +1 though I'm also looking for the corollary, does this understanding of consistency among human organisms negate the zombie possibility. I think, based on your answer, that it does not, but I'd ask you to edit that in before accepting this as the answer
    – That Guy
    Commented Aug 11, 2014 at 5:44
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    It does in the empirical/scientific form of proof, but not in the logical/rigourous form of proof.
    – Dave
    Commented Aug 11, 2014 at 13:34
  • That's all I'm looking for of course. I would just like you to spell it out please
    – That Guy
    Commented Aug 11, 2014 at 14:34
  • Also, geocentrism I think is more debatable; it could be that the likelihood of complex self-replicating beings (life) is so low that it's likely to occur on 1 out of a few billion planets. The likelihood of my own mind having a fundamentally different quality than those of every other member of my species is a different story, as you've pointed out
    – That Guy
    Commented Aug 11, 2014 at 15:27
  • Also, I don't have any direct observation of other earth like planets, but I have direct observations of thousands of other people, who according to what my senses say, are quite similar to me.
    – gnasher729
    Commented Sep 25, 2014 at 16:27

Analogy is one of Bertrand Russell's five postulates that validate scientific method. It states that "the behavior of other people is in many ways analogous to our own, and we suppose that it must have analogous causes." This is the postulate that the belief in the minds of others requires. (Source: Russell bertrand. _Human, Knowlege, Its scope and limits. New york: simmon and schuster, 1948)

Like all Russell's philosophical scrutiny, such a postulate only exposes doubt. On one occasion, Russell admitted that it would have been far easier for him to grow intimate with a cat or a dog or a horse than with one of the half-nomads he saw on the sand bank of the Volga.

In another writing, Russell suggests that "perhaps one could stretch the comprehensiveness that constitutes wisdom to include not only intellect but also feelings." He points out that "it is by no means uncommon to find men whose knowledge is wide but feelings are narrow." "Such men," he writes, "lack what I am calling wisdom." (Source: Russell, Bertrand. Portraits from memory. Knowledge and wisdom. New York: Simon and schuster, 1956)

  • I think the moral is experience matters, age matters, cultural exposure matters. Sympathy is something spontaneous you either have or you don'T have. Like the Russian proverb says, tact and dignity are taught by the heart not by the dancing master. Commented Sep 21, 2014 at 20:26

It seems to me that you must assume other human beings are sentient, or explain why you consistently wish to subvert your own efforts. If you are the source of all willful action, and we are zombies, then you need a good reason for your own self-destructiveness when we compete with you or resist your will. If we do not have goals of our own, why would our actions so consistently defy yours?

Human action cannot be explained as a simple, mechanical process, or it would be much simpler -- it is goal directed and solves problems on purpose. Any reduction that would allow for us to be mere mechanisms, would reduce you to one as well.

You might suppose you and Satan (or Entropy or whatever equivalent is convenient) are the only two sentient beings around, and we are agents of his, but then you would need a good reason why he would not simply compete with you directly. The level of detail he needs to maintain to keep all of the zombies in convincing personality traits is a complete waste of effort he could deploy more effectively.

Assuming Satan is more independent of you than directly competitive does not help. If we are simply fragments of a single separate will, we are still separate from you, and will is not a uniform thing, so you might as well consider each of us, or each critical mass of us who seem to agree, a separate will, as to assume there is a single complex will involved. And even if I am an epiphenomenon of a deeper sentience, I embody sentience.


One liner: If it looks like a duck, swims like a duck, walks like a duck and quacks like a duck then it must be a duck, until it is proven otherwise.


If you are asking for a foolproof answer to hard solipsism then you are out of luck, there isn't one. You may indeed be the only sentient brain in the universe and the rest of us are just figments of your deluded imagination.

That said, if you except that everyone else exists physically then you have to agree that the idea that of the 6.5 billion humans on the planet, you are the only one to develop a conscious mind (given we all share the same basic cranial hardware) is statistically very unlikely.

  • How is your answer different than @Dave's?
    – That Guy
    Commented Aug 11, 2014 at 15:02

If it were the case that the "others" were indeed philosophical zombies, you wouldn't have found it worthwhile to ask "others" the question you posed. Surely, we might appear to enter this discussion, but why would you listen to us zombies who lack the experience that you can refer to while we cannot? Our answers might be even reasonable but wouldn't be convincing or relevant to you.


There is no logical proof, but there are good rational approximations of proofs. As has been mentioned before, Occhams' razor is an argument here: it's much simpler to assume that since others act like I do, look like me, etc. then they must be conscious, like me; than to assume that one way or another, they would look as if they were conscious, but actually aren't, because to assume this you would have to describe the "one way or another", and this would not be simple. There's also the idea that no particular person is special among others (well you can be extremely skillful at gymnastics, but others will be too). But one could say: it would be unreasonable to assume that others aren't conscious, but it would be illogical to assume otherwise.

  • "But one could say: it would be unreasonable to assume that others aren't conscious, but it would be illogical to assume otherwise." - Could you bv explain what that means?
    – Johnny5454
    Commented Oct 27, 2022 at 12:41

Never, ever look at a matter with a theory already made or even half-made.

How do you then know what you are looking for? More precisely, how would you decide which properties of data to focus on? After all, you cannot focus at everything, by definition.

The answer is use a test. It will answer your question. Have a test thats fast enough and have a clear answer (don't have a mix answer).

Your energy should be used, at first and foremost on making that test.

Here is the test for your question: "Are they individually unique?" "Do they have enough individuality to tackle the same problem in different-than-other ways?".

Precisely, if they can make new tests to analyze their hypothesis and solutions, that is, to look at data, tests that they create, not copy, not simulate then they must be thinking on their own.

If on enough tests and enough complicated tests they all present same solution then they might be just acting on instinct, who knows?

A negative cannot be proved (unless you have full knowledge of system, which nobody can claim to have for over 8 billion humans). A positive can be. If your test find even one positive result (yes, they do have novel solutions) beyond test-errors then you have a conclusion. If hundreds of your tests show a negative result then you can reasonably conclude that your research showed a negative with open mind towards further data if and when it comes.


Your question assumes a false standard of rationality and a false epistemology.

You are assuming justificationism: the idea that it is possible and desirable to prove ideas true or probably true. For example, you talk about using induction, which supposedly makes ideas true or probably true by some process involving observation. In reality, you can't prove any position or show it is probable. Any argument requires premises and rules of inference and it doesn't prove (or make probable) those premises or rules of inference. If you're going to say they're self evident then you are acting in a dogmatic manner that will prevent you from spotting some mistakes. If you don't say they are self evident then you would have to prove those premises and rules of inference by another argument that would bring up a similar problem with respect to its premises and rules of inference.

In reality knowledge grows by processes that create variations on existing knowledge and then select among those variations. When a person creates knowledge he does this by guessing variations that might improve his ideas and then selecting among those variations according to whatever criteria he prefers. People thereby can and do guess about the properties of things they have never seen and can never see, such as the core of the sun, or whether other people are conscious.

The standard of rationality is not whether you have justified a belief but whether you would reject it if it was successfully criticised and whether you are interested in looking for criticism. It is not enough simply to state that there might conceivably be some unknown criticism or some unknown alternative solution of some problem. That would be true for absolutely any position you adopt and so that standard is worthless for criticising anything.

Why would you think other people are conscious? They talk about ideas and stuff and the only available account of why they do this is that they think. They talk about sensations and emotions and stuff like that and the only account we have of why they would do this is that they have sensations and emotions.


Since the time of Plato and the introduction philosophical principles of investigation. It is interesting to wonder if Zoomie philosophy and how do we know we're human have been debated. Geocentrism is a good point of reference, for do I have a mind or not? Am I a zoomie or not? Is this just flat earth speculation. David Bohm put forward the idea that Mind and physics are never ending possibilities on a work of physics and philosophy with Basil Hiley. His work on the ontology of quantum mechanics, on its interpretation as relating to the nature of reality, such as God, was opposed by the current and established Copenhegen interepration concerned only with measurement and probabilities (epistomology). It says that quantum mechanics in its present state is all that is, that there's nothing deeper than (delta_p.delta_x <= h_bar/2). On no scientific grounds at all but one of preference of philosophy.

Coming back to the main point "Obviously I'm not looking for a valid deductive proof using formal logic, but at least a relatively convincing argument. How do I know that humans who I encounter other than myself have sentient minds, and aren't just unfeeling zombies?"

Atheism and nothingness after death, seems to me, close to nothingness is nirvana in the eastern philosophies; Tao Te Ching another philosophical principle speaks of the Dao. Paradox. So how does this relate to how do I know I'm not a zoombie and that all other people have sentients minds? I am a zoombie, and I don't like it when other people persecute me by stigma!

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    Hi Brendan. Welcome to philisophy.SE! I just want to point out a few site guidelines. 1) Please don't elaborate on a discussion by posting a new answer - use the comments section for that or, even better, edit your original answer 2) We prefer answers that are referenced from the philosophical literature to answers that stem from personal views. That does not mean that your personal view is wrong, but it is better if you can provide references from the literature that supports it. Please don't take this as a criticism of your view but rather as advice on how to construct a good answer.
    – firtydank
    Commented Aug 11, 2014 at 10:21

Your senses will tell you that there are many people in the world who as far as your senses tell you, are not much different from yourself.

There's the possibility that what your senses tell you is all fake. You are just a computer simulation. In that case, others may not have sentient minds, but nor have you.

The other possibility is that what your senses tell you is right. There are many, you probably have direct evidence of thousands, who are not much different from yourself, as far as your senses are concerned. Your senses cannot detect sentient minds and thinking, but the others behave as if they had sentient minds like you (well, mostly). There is no good reason that they would be different from you in this important aspect.

Beyond that, ask yourself what happens if you act under the assumption that they have no sentient minds. Surely it isn't bad to "kill" a being without a sentient mind. Problem for you, there are all these non-sentient policemen who will catch you and throw you in a cell. Or if you insist they are non-sentient, they will put you in a straightjacket and you enter a different kind of cell that will be even harder for you to leave.


Recall that without assumptions there can be no conclusions. Hence, knowing that a belief in something requires assumptions, one can go all the way and assume this as an axiom.

However, what you were probably looking for was the minimal possible set of assumptions from which one could deduce this conclusion. In this case, you are faced with the problem of defining unambiguously exactly what consciousness is. In the absence of such a definition, your two possible conclusions above become equivalent.


To quote another answer

an assumption of uniformity of properties across the class of objects we call humans -- which is a more simple hypothesis that is consistent with all of our observations

Inducing they have minds (like I do), and justifying that induction based on inference to the best explanation (it is parismonious).

You might go the other way:

assume that others are not absolutely disimilar to me, in which case how do I account for that claim, our relative uniformity? It may not be as scientific (to say that I explain my empathy, my likeness, with other minds rather than puppet bodies etc.), and it relies on explanatory power rather than simplicity, but it also could have more psychological take (solipsists are less likely to experience the requisite empathy).

A mixture of induction and abduction is probably best, and quite how philosophical approaches differ I don't know. But the key point is not to artificially limit yourself to one argument (else when your girlfriend turns out to be a robot, you've lose the game).


Reasonable = with supporting reasons.

Are there ANY reason to even begin to suspect that you are the 1 special thinking entity, and all else is your imagination?

(NOTE: the question is rhetoric).

If not... the lack of reasons... that is the reason to suspect you are not the Creator of all reality.



1) First, lets assume you are not a brain in a jar, but part of life evolving on earth.

2) qualia (your sentience) evolved by evolution, since it provided some evolutionary advantage.

3) therefore, you are not the only human with qualia / sentience.

That said, many people deny the existence of qualia, including notable philosophers and scientists.

Here is an incredible "Closer to Truth" interview with Marvin Minsky where he explains away qualia: https://www.youtube.com/watch?v=SNWVvZi3HX8

Dennett wrote "My view, put bluntly, is that there is no phenomenological manifold in any such relation to our reports", which prompted Chalmers to propose jokingly "Perhaps Dennett is a zombie" in his book The Conscious Mind.

But I think that when highly intelligent people, who spent their life thinking about these things deny qualia, we should take them by their word and acknowledge it is possible they do not have it.

Most of my friends, many of whom are software engineers, either deny the concept of qualia, or acknowledge it but insist that they do not see any reason why a hypothetical computer running the right piece of software shouldn't have what they term as qualia.

So, there is a good argument for people having qualia, while it is conceivable that not all people have the same type of inner experience you do.

  • "we should take then by their word and acknowledge it is possible they do not have it"- I think your making a mistake here. Daniel Dennett experiences the world in much the same way as I do, he just doesn't believe that qualia are independent from the brain's already understood functions because it's a form of the brain's tricking itself. He's not claiming that he's a zombie, he's saying the whole questions of zombies is irrelevant
    – That Guy
    Commented Aug 11, 2014 at 21:27
  • @Matt, he actually did claim he is a zombie in Consciousness Explained “Are zombies possible? They're not just possible, they're actual. We're all zombies. Nobody is conscious — not in the systematically mysterious way that supports such doctrines as epiphenomenalism. *It would be an act of desperate intellectual dishonesty to quote this assertion out of context!”, I think it is generally accepted that qualia is not independent from brain functions, so I do not find any sense in the rest of your comment, but a pointer to Dennett will do; cheers
    – nir
    Commented Aug 11, 2014 at 21:52
  • I just meant that he's not claiming that he's a zombie in the sense that he's denying that he himself has experiences. I just wanted to make sure that you didn't think that Dennett experienced the world in a fundamentally different way than I do, but I see that we're on the same page here
    – That Guy
    Commented Aug 11, 2014 at 23:28
  • @Matt, We are not on the same page at all; while I actually agree with the quote in my previous comment when read in context of his discussion of epiphenomenal qualia [p398-p406], he also asserts "Anyone or anything that has such a virtual machine as its control system is conscious in the fullest sense" [p281] referring to a Joycean machine which (if I understood correctly) may be implemented by a Turing machine. If I am correct, then he is either dead-wrong or has a different kind of inner experience than myself, otherwise I would appreciate an explanation and a reference.
    – nir
    Commented Aug 12, 2014 at 13:31

In my opinion, there is no way to prove conscience. There is no way to prove sentience. Are you sentient, or do you just think that? Do other people think that too? There is no test of sentience, as it is proven that artificial intelligence test designed by Turing are beatable. In truth, there can never be an answer. Are you alone a thinker? Are you a thinker in a sea of thinkers? Do you even think, or is a trick to feign you by your own instincts?

  • Welcome to Philosophy.SE. It might be helpful if you could explain some of the thoughts you mention in passing. You present a number of questions but don't investigate any of them - this makes it a bit hard to see what you're getting at exactly.
    – commando
    Commented Mar 4, 2017 at 19:06
  • I am presenting questions as to draw ones attention to these equally important questions which are in parallelism with the original question. Commented Mar 22, 2017 at 12:49

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