I remember years ago I read somewhere that, 'Objects don't exist when we are not looking at them', is an old philosophical idea. I have heard that it probably comes from Berkeley or is based on something he said. Did he say this or anything like it?

EDIT: I've been thinking that it must have occurred to the Greek philosophers first, since it's a very simple idea.

  • I think babies were the first to come up with this concept, or perhaps the animal kingdom before we evolved – Callum Bradbury Apr 18 '18 at 13:44
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    Maybe George Berkeley 's view (attributed to him the slogan : esse est percipi): "All knowledge comes from perception; what we perceive are ideas, not things in themselves; a thing in itself must be outside experience; so the world only consists of ideas and minds that perceive those ideas; a thing only exists so far as it perceives or is perceived." – Mauro ALLEGRANZA Apr 18 '18 at 13:48
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    See the discussion in George Berkeley idealism : Unperceived objects. – Mauro ALLEGRANZA Apr 18 '18 at 14:17
  • Also, this is a view stated (to be critiqued) by Hegel in the preface to the phenomenology called "Sense Certainty" – virmaior Apr 19 '18 at 0:48
  • @Asmani. The view is a version, not quite right, of the position of Berkeley. I have rephrased it so that readers will make the connection with Berkeley and give your question, to your own benefit, more attention than it's likely to get otherwise. Just trying to help. But you can change it back if you object. Best - Geoff – Geoffrey Thomas Apr 20 '18 at 7:30

The quote in the Question looks like a highly approximate summary of Berkeley's idealism - esse est percipi : to be [exist] is to be perceived - but Berkeley did not link epistemology and ontology so tightly as the Question quote suggests.

The 'esse est percipi' principle first appears in Berkeley's Philosophical Commentaries (Entry 429). We should note that in The Principles of Human Knowledge it makes its initial appearance in I §2 : 'the existence of an idea consists in being perceived'. It is only by a course of argument that Berkeley infers that sensible objects are nothing but (what he early on calls) 'collections of ideas' (Principles, Intro.§1) and hence that for them too, as ideas, to be is to be perceived.

A fuller version of the principle is 'esse est percipi aut percipere' : to be is to be perceived or to perceive (Philosophical Commentaries, Entry 429). But the shorter version is right for the Question.


'To be is to be perceived' means just that : perception is not confined to sight and looking. We can perceive by or through any of the senses. I can perceive a table by touching it; I can perceive a door, when I am blindfolded, by its resistance.


Sensible things, objects of perception, Berkeley tells us :

... cannot exist otherwise than in a mind perceiving them. I think an intuitive knowledge may be obtained of this, by any one that shall attend to what is meant by the term exist when applied to sensible things. The table I write on, I say, exists, that is, I see and feel it; and if I were out of my study I should say it existed, meaning thereby . . . that some other spirit actually does perceive it. (The Principles of Human Knowledge, I §3.)

That 'other spirit' could be non-human and a likely candidate is God :

'Since sensible things do not have independent existence in Berkeley's view but exist only as collections or congeries of ideas in the mind, he concludes that some sensible things must exist continuously in the infinite mind of God, at least during those intervals of time when they are not perceived by finite minds' (Dale Jacquette, 'Berkeley's Continuity Argument for the Existence of God', The Journal of Religion, Vol. 65, No. 1 (Jan., 1985), 1.)

So ontology (the existence of sensible objects) is not tied to epistemology (human perception). Hence my remark at tat start that Berkeley did not link epistemology and ontology so tightly as the Question quote suggests. But we might note that 'some other spirit' does not logically imply that it is the same other spirit, namely God. There could be a multiplicity of such spirits.


The Question mentions a possible anticipation of Berkeley's view in Ancient Greek philosophy. Plato's Theaetetus comes to mind. Here's Miles Burnyeat on the point :

In the first part of the dialogue a theory is elaborated according to which nothing exists outside the particular perceptual encounter in which it appears to sense. (M. F. Burnyeat, 'Idealism and Greek Philosophy: What Descartes Saw and Berkeley Missed', The Philosophical Review, Vol. 91, No. 1 (Jan., 1982), 4.)

The context is Theaetetus' definition (151e) of knowledge as perception.


Berkeley takes for granted that sensible things exist continuously when not perceived by finite minds. There is no logical necessity to assume this. Perhaps they do pass into and out of existence according as they are perceived by finite minds. It may be counter-intuitive, but so ?


We are all familiar with the 'myth of the given', we know about the theory-ladnenness of observation, we know that perception involves inference (as when I see that a poker is hot). But there is, or so it seems to me, an irreducibly passive element in perception. If we are to perceive something then, it strikes me, there must be something to be perceived, something which is not purely a product of our own minds. Something is given in perception - presented to consciousness - if nothing like as much as was once widely thought.

Now, this does not fit well with the idea of God, 'that active principle' (Principles, I §66). God is on Berkeley's account a purely and wholly active mind or spirit. Nothing is or can be presented to the consciousness of such a being. Therefore God does not perceive and is incapable of perception. It follows that God does not perceive sensible objects, and ensure their continuous existence, in our absence.


G. Berkeley, The Principles of Human Knowledge, 1710.

G. Dicker, Berkeley's Idealism: A Critical Examination ISBN 10: 0195381459 / ISBN 13: 9780195381450 Published by Oxford University Press, 2011

Dale Jacquette, 'Berkeley's Continuity Argument for the Existence of God', The Journal of Religion, Vol. 65, No. 1 (Jan., 1985).

Jonathan Bennett, 'Berkeley and God', Philosophy, Vol. 40, No. 153 (Jul., 1965), pp. 207-221.

George Pitcher, Berkeley, London : Routledge, 1977.


The origin of “objects don't exist when we are not looking at them”

Probably the best place to start is Wikipedia, "Direct and indirect realism". The Internet Encyclopedia of Philosophy has an in-depth entry that includes references ("Objects of Perception"). http://www.iep.utm.edu/perc-obj/#H2. The IEP discussion includes indirect realism.

More recently, indirect realism has been considered by scientists. Discover magazine (June 2002), "Does the Universe Exist if We're Not Looking?" http://discovermagazine.com/2002/jun/featuniverse
Daily Mail (2 June 2015), "Your entire life is an ILLUSION: New test backs up theory that the world doesn’t exist until we look at it" http://www.dailymail.co.uk/sciencetech/article-3107996/Our-entire-lives-ILLUSION-New-test-backs-theory-reality-doesn-t-exist-look-it.html

  • Hmm, I'm certain that second link has nothing to do with perception, it's just badly written. The "observer" as relevant to that experiment is anything which interacts with the particle, so would include interactions between a photon and an inanimate detector, or the surface of a rock. The first link is an example of a scientist considering the idea, and doing so without experimental evidence to back that idea up. – Harabeck Apr 19 '18 at 21:50
  • I do not think OP's "origin" refers to a place to start looking (and Wikipedia?). And it certainly is older than 2002. – Conifold Apr 19 '18 at 22:16
  • @Conifold . It seemed to me that Asmani was asking for a history of the idea. The Wikipedia entry has some background about it, and so is a good place to start. – Mark Andrews Apr 20 '18 at 0:21

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