If a tree falls in a forest and no one is around to hear it, does it make a sound?

Of course it does, assuming that there is no freak occurrence like the wind blowing in just the right direction for it to silently fall down. In general, yes, it will make a sound, regardless of whether anyone or anything is around to hear it. The same physical actions take place, creating a "sound", irrespective of the presence of a human/observer of any species.

It's just that nobody happens to hear it because they aren't there at the moment.

I seriously, 100% honestly don't understand the "point" of this so-called thought experience. Maybe I'm missing something, but to me, it sounds like somebody misunderstood what "philosophy" means. Or maybe I'm the one who misunderstands it...

Do they mean that we cannot know for sure that the tree did make a noise, because we weren't there and (supposedly) weren't allowed to have recording equipment there to detect the fall and its expected sound? Do they mean that maybe a fox ran by and dampened the tree's fall so it didn't make a sound loud enough?

It seems so pointless to ask if the tree makes a sound if nobody is around, because literally nothing indicates that it would matter that a human is around to hear it for it to make the sound. It seems like a parody of a thought experiment to me.

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    I think the ambiguity of the question is that the word "sound" can be interpreted to mean a density wave in air, or to mean the qualia we experience when such waves hit our ears (see the philosophical distinction between primary and secondary qualities). As an analogy one might ask whether a stop sign is still red when the only one looking at it is someone with red/blue colorblindness--"red" as in the normal visual experience isn't inherent in light of that correct wavelength.
    – Hypnosifl
    Commented May 14, 2020 at 0:10
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    Your question could be more useful and focused if you first read existing explanations such as on Wikipedia: en.m.wikipedia.org/wiki/If_a_tree_falls_in_a_forest , and then ask about the sentence describing which part of the explanation you don't understand.
    – tkruse
    Commented May 14, 2020 at 0:47
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    wow, for some inane reason i always thought this was a koan
    – user46524
    Commented May 14, 2020 at 0:49
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    First, it is not a 'thought experiment'. There is no experiment It is a question posed as to whether an event occurs if there is no observer to the event. Google Schroedinger's cat for a better understanding. Commented May 15, 2020 at 4:20
  • If sound is a reproduction of a wave which requires a receptor in order to become activated, then if there is no human presence when a tree falls, the wave produced will pass harmlessly on until its energy expires, without any sound. CMS
    – user37981
    Commented May 16, 2020 at 15:12

5 Answers 5


The point is this: the existence of an object is not something that is independent of a subject.

Colors exist because our eyes are able to process some physical phenomena and interpret it as a color manifestation. Otherwise, outside there's only energy (and perhaps not even that). Smells depend on our cells. etc.

And sound is the same. Sound depends on the ears of someone. Air vibration is not sound per se. Sound depends on memory! (an instantaneous vibration is not possible) Air molecules vibrate all the time and that doesn't mean there's sound out there. You will say, "yes, sound is made by but certain types of organized vibrations, in this and that range, with this and this attributes". There it is! who defines the attributes for a vibration to be considered as a sound? Not only the human ears, but also the human brain! Who defines what is a frequency? The size of our ears! Our sense of time! No sound is possible without ears and a mind. No smell exists without a nose. No objects, no space, no time exist without a human body.

Most people normally think that things just exist without an observer, but as soon as such fact is dissected, it starts to lose sense. This is a classical philosophical issue that is addressed mainly by epistemology. Locke proposed an approach in which objects had primary and secondary qualities, primary being those that can be measured, and secondary, those that clearly depend on the subject. But such idea was quickly rejected by other philosophers. Berkeley did better: he suggested that matter does not exist at all. A known phrase is usually attributed to him: "esse est percipi", to be, is to be perceived. Berkeley is called an immaterialist.

In simpler words, objects do not exist without a subject. If you are interested in such view, read about the philosophical current known as empiricism (Locke, Berkeley, Hume), which states that knowledge depends entirely on experience, that any possible concept depends on a mind, and even that things cease to exist as soon as you cease to perceive them rationally (e.g. during sleep). Most modern forms of philosophy are based on such ideas. Check also Kant, who demonstrates the inevitable dependency of space and time on human reason.

  • Well said! It's a chair because we construct a chair in our mind; it's atoms in the shape of chair because we construct atoms in the shape of a chair in our mind.
    – J D
    Commented May 14, 2020 at 16:18
  • Could maybe use some clarification on what you mean by "things" or "objects"--science has undermined the idea of natural kinds and with it the notion that some groupings of particles are more "natural" than others, but the particles themselves are still held by most realists to have some sort of objective existence independent of any human observer, and if one assigns some objective reality to mathematics, any arbitrary set of particles also might be seen to have some kind of objective existence.
    – Hypnosifl
    Commented May 14, 2020 at 20:59
  • @Hypnosifl: I don't use the terms objects or things independently of a subject; objects or things come to be just beliefs, subjective ideas; obviously not in the domain of by science. The necessary subjectivity to understand something as an object is not part of science; science deals w/empirical truths, which are not necessarily final truths, and the boundary object/subject is another complex topic. The system theory would be the most objective approach to objects, but if you think it, systems are still subjective ideas. Nature is just quarks. Reason groups perceptions into systems.
    – RodolfoAP
    Commented May 15, 2020 at 5:31
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    "Nature is just quarks" is just an assertion of an ontological assumption, it's not even clear this is the metaphysics that best fits with the spirit of modern science given the way entanglement may suggest particles should not be viewed as basically separate things that only occasionally interact when they get near each other (why does 'nature is just quarks' seem more plausible than 'just quantum state vectors' or 'just quantum fields' or 'just events' for ex.?) See Ross & Ladyman's book Every Thing Must Go for an diff. way of trying to come up with a metaphysics that fits modern science.
    – Hypnosifl
    Commented May 15, 2020 at 6:03
  • @Hypnosifl: that's precisely what I've meant: out there (out of each one's body), the universe is made of something, but it is not things or objects. Kant calls that the noumenon or the thing in itself. Agree.
    – RodolfoAP
    Commented May 15, 2020 at 13:59

According to the Wikipedia article on this, several philosophical questions are highlighted by this thought experiment https://en.m.wikipedia.org/wiki/If_a_tree_falls_in_a_forest

Can something exist without being perceived by consciousness?

This does not seem so important for trees in woods, but the philosophical question extends to alien life on other planets or things like good, angels, demons, ... If nobody is there to see them, do they exist? How about hallucinations, do they exist because they are perceived? It can also extends to the limits of what we can maximally know about our universe, or our lives. This can also highlight the problem with qualia: how to describe the difference in perception between red and green to a colorblind person? Or to a blind person? Are there maybe more colors than currently known which we could experience by manipulating light?

Can we assume the unobserved world functions the same as the observed world?

Again this seems not so important for trees in woods, but how does the world function on quantum scale, or inside a black hole, under zero gravity, on other planets, or during the big bang, or "before" the big bang? Can science really know such things without anyone directly observing those areas?

What is the difference between what something is, and how it appears?

As an example, as a witness in a courtroom, it's different to say"I heard a loud bang" or "There was a pistol shot".

The tree sentence can have the purpose of dealing with the "basics" of complex questions, like what words to use, before moving on to more complex problems.

  • I saw some words (above), so I wrote some words. I finally understand humanity, I've just been making assumptions all this time! :-)
    – Scott Rowe
    Commented Oct 20, 2023 at 16:27

No, it doesn't. There are two different things to consider. Mechanical vibrations generated by the falling of tree, and detection of those vibrations by human ear. It's the latter which we call as sound.

Imagine two people standing next to each other with different hearing range say 20Hz-20kHz and 20Hz-22kHz. If an otherwise undetectable event takes place which generates a 21kHz wave, the statement "There was a sound" is true for person 2, but false for person 1; note that their is no objective/universal truth for this statement, there are vibrations roaming around right now which are below or above your hearing range.

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    So if sound depends on the observer, nothing makes a sound - sound can only be perceived. In this interpretation, a tree falling next to a person doesn't make a sound either. It makes vibrations in the air (just like the tree with no one nearby), but it only becomes a "sound" when it's heard. Under this definition, sound cannot be made, but only heard. Commented May 14, 2020 at 20:19
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    @NuclearWang Language works like this. We also say "A stop sign is red" although there's nothing physically red to that sign. Making a sound is causal speak here, ie. this tree falling caused me to perceive that sound. It might be helpful to distinguish between necessary and sufficient conditions as well.
    – Philip Klöcking
    Commented May 15, 2020 at 13:14

According to a conventional definition of the term "sound"

When we define sound as the sensation of hearing by an observer when vibrating air hits the eardrums and is perceived by the mind then

the air vibrations of a tree falling in the forest would not make a sound if there is no one hear to hear it. It is not an actual sound until the vibrating air reaches an eardrum and is heard.

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    No, your own definitions only says that they can be heard when they reach someone's ears. It doesn't say that they have to reach someone's ears! Commented May 14, 2020 at 14:04
  • @curiousdannii Yes you are correct. I didn't notice that because I always use my own definition instead of trying to cite others. I changed it back to my own definition. It would be great if you could reverse your vote on the basis that it no longer applies.
    – polcott
    Commented May 14, 2020 at 15:49

Without a measuring device to record it, there is a sense in which the recognisable properties of quantum particles such as electrons do not exist, just as the falling tree makes no sound at all.

‘Reality is merely an illusion,’ Einstein once admitted, ‘albeit a very persistent one.’


  • No, unless the tree falling was triggered by a quantum event.
    – tkruse
    Commented May 14, 2020 at 1:16
  • @tkruse Ah yes I forgot that detail.
    – polcott
    Commented May 14, 2020 at 2:35
  • It is triggered by lots of quantum events.
    – Scott Rowe
    Commented Oct 20, 2023 at 16:22

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