Are there mind-independent physical objects?

Keir Martland

I’ve been sorting through my AS Philosophy file and this short essay, with which I was most pleased, fell out onto the floor. This is from when we revisited the ‘Theories of Perception’. You may recall that I once suggested that there were elements of truth to both direct and indirect realism. This essay may come as a bit of a surprise.

While objects exist, there can be no question their being independent of our minds. Objects are collections of sense experiences and as such are completely mind-dependent. It necessarily follows that, as the immediate objects of perception are mind-dependent, any talk of an external world independent of our minds and beyond our perception is meaningless.

One of the two realist theories of perception is direct realism. According to this view, there are mind-independent physical objects. These objects are the immediate objects of our perception and we perceive them directly and with no intermediary. We perceive these objects exactly as they are and every perceiver perceives these objects in the same way.

Yet, direct realism provides us with no reason to accept that there are mind-independent physical objects. A direct realist might say that we are aware of these objects, but this begs the question. In other words, in order to prove the existence of mind-independent physical objects, the direct realist points to ‘mind-independent physical objects’, presupposing their existence. This will not do, especially if one were to adopt the Cartesian method of hyperbolic doubt. Adopting this method, one might concede that one is aware of something, but this something does not have to be a mind-independent physical object. At the very most, all we can do is infer the existence of mind-independent physical objects, as the indirect realist would have us do.

Indirect realists claim that we have a perceptual awareness of mind-independent physical objects, but that this is an indirect awareness. There is an intermediary between the perceiver and the thing perceived which the indirect realist calls ‘sense data’.

All we are ever aware of, according to the indirect realist, are sense data: we see a tree because of sense data; we feel heat because of sense data; we hear music because of sense data. Yet, if this were the case and if there existed a mind-independent external world, then we would never know how accurate our perception was as a representation of that external world. This is because if all we are ever aware of are sense data, and if sense data are not the same as mind-independent physical objects, then two things follow directly: first, we can never perceive the ‘real’ world directly; second, we cannot perceive both our sense data and this real world simultaneously. As a consequence, we cannot compare our perception with the external or ‘real’ world to see how accurate it is. Thus we must accept, if we are indirect realists, that we can neither know how accurate our perception is nor what the ‘real’ world is actually like.

There exists an even more fundamental problem with the indirect realist’s theory. The existence of mind-independent physical objects is still not evidenced. Cartesian hyperbolic doubt is still applicable here. Might it not be the case that sense data is put into our minds by the Evil Demon to trick us? Indeed, the indirect realist has even less ‘evidence’ at his disposal than the direct realist. For the direct realist, our perception is the ‘proof’; we perceive a tree because there is a real, mind-independent tree in front of us. For the indirect realist, however, we only directly perceive sense data, which are caused by and supposedly represent some mind-independent physical object which does not necessarily resemble the sense data and which we can never directly perceive.

Thus it is actually the case that the indirect realist has built up a completely non-falsifiable theory for which there is no evidence. This seems as good a reason as any to reject indirect realism as a possible proof of the existence of mind-independent physical objects.

What remains (excluding the more modern theory called ‘phenomenalism’) is idealism. Idealism is an anti-realist theory of perception. Idealists, therefore do not maintain that there exist mind-independent physical objects. Rather, for the idealist, there are objects, but these are collections of sense experiences which we also call ideas. Idealists do not infer the existence of matter like the indirect realists and nor do they assert its existence like the direct realists.

For Berkeley, the founder of idealism, “esse ist percipi”: to be is to be perceived. That is to say that existence is dependent upon being perceived. Since there is no way in which we can perceive a mind-independent physical object in the way we can perceive colours, shapes, and sizes, mind-independent physical objects are not objects of our perception. Since to be is to be perceived, it follows, therefore, that mind-independent physical objects do not, in fact, exist.

Moreover, in the Master Argument, Berkeley demonstrates that mind-independent physical objects not only don’t exist, but cannot exist. Berkeley asks us to imagine an object independent of any mind. However, the object you have just imagined is not independent of any mind since it is dependent upon your mind. This way, a mind-independent object is not an object at all, since no one is perceiving it.

A mind-independent physical object is no object at all, since to be is to be perceived. Not only is the idea of a mind-independent physical object problematic, but there is also no evidence for the existence of such objects. Neither pointing at an object and labelling it a mind-independent physical object nor inferring the existence of such objects from sense data are strong enough to counter the Master Argument, which is self-evidently true and whose truth can be discovered without empirical testing.


  1. Erm.
    A thing either “is”, or it “isn’t”. If it “is”, then it “is” what it “is”. The same sorts of animal who can do “perceiving stuff” will see it as it, er, “is”. A fruit fly is what it is, for example. If you are a birdle, then you eat it…or you hoover up the larvae which is much quicker and probably tastier as there’s no hard or gristly bits… If you are a human, then you swat it, if you can outdistance it in a few inches (you can’t). If you are a molecular biophysicist human, you breed trillions of it in a vat of rotten pears and then you do stuff.

    But it’s a fruit fly.

    I’m wondering what all this stuff is about that they set you young people to learn about, Keir!

    • Idealists do not deny the existence of things. They still talk about objects. They still talk about perception. They still talk about a reality. They even talk about objectivity. But what distinguishes a realist from an idealist is their take on these things called ‘mind-independent physical objects’. I’ve never seen one of those before in my life. I’ve seen plenty of objects though.

  2. The thing with objects Keir is that we see ‘them’ based on the following things:

    Earning it
    Winning it
    Everyday use
    Right and wrong

    I don’t believe it is worth going really into depth with objects apart from using the list above unless you have time to waste.

    • Questions of objectivity, truth, justice, morality, etc, are, indeed, incredibly important. However, they are quite separate from the subject under discussion.

      The question I was addressing is ‘of what do we have a direct perceptual awareness’?

      The value of that question is, I’ll grant you, less obvious than say ‘Is there such a thing as meaning?’ but it is worth exploring.

      It’s also interesting to see where the philosophers stand on perception. Locke was an indirect realist. Russell was, too. Almost nobody is or was a direct realist. Berkeley was an idealist.

      The wider significance of the theories of perception?

      Well, Locke was also an empiricist and so was Russell. It would seem that empiricism stems from the view that we only infer the existence of that which is real, or that reality is, to quote Russell, “the best hypothesis.”

      Berkeley was an empiricist, too, sadly. Yet, he argued like a rationalist. He argued that the idea of a mind-independent X is incoherent, a priori. Without question begging it is impossible to refute Berkeley’s Master Argument.

      Kant, incidentally, seems quite muddled on perception.

      • I get the philosophy of what you are addressing when it comes to direct perceptual awareness and the use of objects.

        I’ll give you an example of my perception of things; if I go to a church event at someones home, I know what to expect because there will be use of a Bible, we would have food and drink and we talk about what God and his ways. My perception is that I am in familiar surroundings with objects I am fully aware of and we can have a good night with my friends and loved ones.

        Now for something different, I play Basketball every Friday and straight away, I don’t know who is turning up and for that I don’t know who I am against, what ball we are playing or what sort of position I am expected to play. My perception is one of intrigue and curiosity of which I gain a new experience everytime as I do believe the word empiricist is derived from the greek translation for experience.

        Sometimes Keir, people like me would not delve much into these things as we prefer to actually gain from experience to shape our thinking and way of life.

  3. I appreciate that lots of people prefer to talk about experience. It’s probably very natural.

    My only problem is that ‘experience’ is no argument.

    Experience never provides us with certainty; we can only ever induct.

    And it is necessarily subjective; your talk of your own experience will never do anything for me.

    There is also no experience to lead us to believe that knowledge comes from experience. Empiricists ought to point to some ‘experience’ which ‘proves’ the basis of their theory.

    The point of epistemology is, so far as I see it, to refute both ‘common sense’ (whatever we see must be there, whatever we’re told is true etc.) and skepticism.

    So how do we do it? We first need to understand perception. We need to realise that our perception does not guarantee truth, but also that perception has some value.

    Descartes essentially had it right with his “I am, I exist” as the first clear and distinct idea. It’s a pity he was wrong on everything else.

    • This is where you and I would disagree. You say that ‘experience’ is no argument, we can’t carry on developing ideas and theories purely based on ‘perception’ and ‘interests’ because the natural reaction of people would be ‘What would you know if you’ve never experienced it”. There has to be a sense of experience that goes with our sense of beliefs and I would agree that people have all sorts of different experiences whether good or bad.

      Gaining knowledge is about finding out either information that we need to know about or information that we want to know about.

      If you went to a job interview, 10 times out of 10, they would ask what experience do you have this, that or the other. Now all I am doing is telling them what I have done whilst at the same time, they have gained knowledge of what I have done whether it was wanted or needed. In their minds, the more I gave them that information, the better chance I have of getting that job.

      You’re welcome to disagree but as you are interested in perception, I hope you have gained a better knowledge of my knowledge and experience.

  4. Objective reality necessarily exists, as do our minds. But our sense data give us several subjective lenses through which to form a frame of reference and view this objective reality.

    In consequence colour as we see it is subjective, even if the light wave-lengths are objectively real. All our perceptions are subjective, and so the “things” as we recognise them necessarily are too; ‘chairs’, ‘laptops’, ‘feet’, ‘the sky’, and so on.

    Our cognition of cause and effect, and our capacity to harness it to build relationships we can trust to hold with the external world includes things like our mental concepts of objects in the world like ‘chair’, ‘laptop’, ‘feet’ and ‘the sky’. It also includes things like ‘gravity’, ‘solidity’ and ‘comfort’.

    Guess I’m an indirect realist a la Martin Gardner.

    • What you have just proven there Matthew is a word Mr Martland would not agree with and that is ‘experience’. Think about it, you are talking about cause and effect which is curiosity and building relationships which is turning curiosity into building that experience.

      Call me simple, but I am not sure whether it is worth getting into the complexities of perception, knowledge and objects as I believe these things can ask more questions rather than answer them and can lead into confusion.

    • Matthew, then you’ve never really experienced these things. You never will, according to indirect realism. You just infer that there’s a table of which you will never be directly aware. So why bother talking about a mind-independent table if all you are ever aware of are sense data?

      I’ll repeat:

      I’ve never met a mind-independent physical object.

      In the process of perception, all I’ve met are my own sense experiences, which in turn cause ideas.

      I’ve never had any reason to infer the existence of something existing beyond my perception, i.e. outside its remit.

      If anything, there couldn’t be anything weaker than one’s own sense experience on which to base the claim that there exists an external world of mind-independent physical objects whose existence cannot be verified either through deductive argument or sense experience.

      The indirect realists have put together, not only an improbable theory (there are more probable ones, such as direct realism and idealism) but a totally non-falsifiable theory.

      I will not be satisfied until an indirect realist has proved to me that mind-independent physical objects exist. I maintain that they cannot do it without begging the very question under discussion.

  5. Yes there are indeed physical objects independent of the mind perceiving them. When a tree falls in a forest and no one is there to hear it – there is still an air pressure curve.

    The physical universe exists – and when we die, it carries on existing.

    However, the mind also exists.

    Thomas Hobbes who argued that humans were not agents (that we were just flesh robots whose every action was predetermined) was wrong. There is no moral importance in the “freedom” of water after a dam has blown up (indeed such “freedom” is a bad thing), there is moral importance in the freedom of human beings – as we have reason (agency), moral responsibility based upon real CHOICE. This is why tyranny (the absolute unlimited state supported by Thomas Hobbes) is wrong.

    Reason is not a “whore” (Martin Luther) or a “slave” (David Hume).

    Reason, human agency (the ability to do other than we do) exists – and those who deny it are wrong.

    The “Old Whigs” who are argued that human beings were moral agents (that we had a real CHOICE over some of our actions) were correct.

  6. “To be is to be perceived” – simply not true.

    For example the island of Iceland existed before anyone went there.

    • Idealists don’t deny that we can perceive the same objects. These objects are ideas, though. Ideas cannot be caused by other ideas, we grant this. The cause of these ideas may be God and he may keep them in existence as a kind of permanent perceiver.

  7. I think some reading of the Common Sense philosophers from Thomas Reid to Harold Prichard and Sir William David Ross (that old student of Aristotle) is in order.

  8. Keir – the burden of proof is on the Idealist not on the common sense Realist.

    I do NOT have to prove that Iceland was there before the first Viking (or Irish monk) ship landed and people “perceived” it – you Keir have to prove that Iceland did not exist before it was “perceived”.

    And Iceland is not an “idea” – it is a large lump of rock in the sea.

    However, I must confess, I rather like Archbishop B’s backdoor effort to prove the existence of God by making the existence of the material universe dependent upon Him.

    It is a naughty argument and wrong – but………

    Well bags of sweets are rather naughty and wrong to – and I quite like them.

  9. Still waiting for your proof that Iceland did not exist before the first ship got there Keir. Do you actually have any proof that Iceland did not exist before it was “perceived”? Remember the burden of proof is on you – it is not upon me.

    Yes John, just when one thinks that modern physics can not get any more absurd – it does.

    When I take this coffee cup into the kitchen, wash it and shut the door, I (the former “observer”) will be “separated” from the formally observed (the coffee cup) – if modern physics denies this then modern physics is nonsense.

    However, I will no longer be “observing” the coffee cup, so it will no longer be “observed”.

    So modern physics is vindicated!

    As if the “observer” is “separated” from the “observed” (if I take this coffee cup into the kitchen and shut the door) it is no longer the “observed”.

    So “the observer and the observed can not be separated”.

    Poor cat – being neither alive or dead must be very uncomfortable.

    Another amusing thing is that the same “philosophers” who attack the independent existence of the physical universe (implying that only the mind – the “I” exists), will sometimes (without a blush) then turn round attack the existence of the mind (the “I” – the moral agent).

    For example David Hume did both. One minute attacking the existence of the external world (implying that only the mind – the “I” the moral agent) exists, and the next minute attacking the existence of the mind itself (denying a thought means there is a thinker – a moral AGENT, the “I”).

    This is fine if one is just messing about – but one must remember not to take it seriously.

    Ditto with the history of David Hume’s history.

    Louis XVI took it seriously (in fact it was his favourite book) he never understood it was not meant to be taken literally.

    So Louis XVI followed the advice that one must not resist a Parliament (the Hume claim that it was resisting Parliament that got King Charles the First) killed – and that got Louis XVI (and his family – and hundreds of thousands of other people) killed.

    Of course, as David Hume knew perfectly well, it was not fighting the war that got Charles killed – it was LOSING it. And the way to make certain that you lose is to not fight at all (those who refuse to live by the sword can still die by it – indeed they often do).

    So by not fighting his enemies (indeed by forbidding others, such as the Swiss Guard, to do so) Louis XVI was not saving himself – he was dooming himself.

    Louis XVI made the mistake of taking Hume literally.

    It is the same in philosophy.

    David Hume knew perfectly well that the external world existed (independently of any observer).

    And David Hume knew perfectly well that the human agent (the mind – the “I”, agency).

    It is not the fault of the late David Hume that some people take his writing (his elegant game playing) literally.

    • You’re question begging again. (‘prove that the mind-independent such and such did not have a certain trait’) Your notion of the burden of proof is also pretty insane here. Suddenly the B.O.P is on someone to prove a negative…

      • Not at all Keir – my burden of proof is not “insane”, it is that of the ordinary person.

        You claim that things do not exist before they are perceived. That existence depends on being perceived.

        That is a very wild claim.

        It is indeed the claim that (for example) Iceland did not exist before the first ship of Norse (or Irish monks – if one believes that story) got there.

        Now I know you (unlike an atheist) can say “ah but it DID exist – because it was perceived by God”.

        But that is still a wild claim (the claim that “existence depends on something being perceived” – that things do not exist till a mind notices them) and it is claim that ordinary people have no reason to take seriously.

        As for ordinary people generally.

        Philosophers have been sneering at us since at least the time of Plato.

        However, the so called “shadows on the cave wall” are far more likely to be the truth than the wild fantasies of Plato. Just as justice is in fact (contrary to Plato) “hands off” (not aggressing against the bodies or goods of others – as long as they are not going to aggress against you) not the hundred of pages of whatever than Plato presents.

        As Cicero pointed out – some things are so absurd that only a philosopher would believe them.

        I was recently rereading Aristotle’s “Politics” and was reminded of something that stuck me 40 years ago – Lycophron (giving the common sense definition of justice) is correct, and Aristotle’s claim that the state exists to make people “just and good” (by the sort of detailed control of virtually every aspect of society that he presents near the end of the Politics) is not only wrong, it is absurd.

        Cicero was correct – and he was not being complementary towards philosophers. And it was not just a Roman sneering at Greeks – on the contrary Cicero loved Greek culture, including Greek philosophy, but he could he also see when they lost their heads (let their obsession with theories over turn their practical judgement).

        There was a time when philosophers took this on board and tried to make their musings rational in ordinary terms – hence such terms as “Common Sense philosophers” or “ordinary language philosophers”.

        As both Harold Prichard and Sir William David Ross used to say…….

        If a reasonably intelligent person can not just walk in from the street and listen to one my lectures (or pick up one of my books and read it) and know what I am saying, and see it makes sense – then it is ME (the philosopher) who is going wrong, not them.

  10. Of course when one looks at very small particles (with very low mass) one moves them – because the very act of bashing particles of light (photons) into the particles will effect them.

    But that is NOT what Idealist philosophers mean by the external world not existing independently of the observer.

    Determinism is absurd because it, de facto, denies the existence of the human self (the “I” – the moral agent who can choose to do otherwise than he or she does).

    That is the basis of philosophical libertarianism – which is the foundation of political libertarianism.

    Someone who claims they can have political libertarianism without philosophical libertarianism is just wrong. And “scientists” who deny the existence of human choice (real choice) deny their own existence (as human beings) – and should be sent to bed without any supper (I am using a figure of speech – literal minded people).


    Idealism is also absurd.

    Determinism, de facto, denies the existence of human beings (the self – the “I”, real choice).

    Idealism, de facto, denies the existence of anything else.

    The Determinist is a lunatic who denies his own existence (an “I” who denies there is any such thing as “I”).

    The Idealist (at least an Idealist who is also an atheist) is a lunatic who denies the existence of anything else apart from himself. Who denies the independent existence of the universe – who thinks that everything depends, for its very existence, on his observing it.

    David Hume did not really believe any of this – he was just engaging in philosophical exercises (a fancy way of saying that he was playing games).

    What David Hume was actually doing was demanding that people formally PROVE the obvious (the self evident). He did this because he, David Hume, knew well that the really important things are not subject to proof in this sense (and he enjoyed the sight of people trying to “prove” the obvious – such as their own agency).

    Of course the point it is that the obvious does NOT need to be proved – that is why we (Whigs) say “we hold these truths to be self evident” (because they are).

    For example……

    A is A. Something is itself (law of indenity).

    1+1 = 2.

    I exist – even my doubting my existence shows that I exist.

    And on and on……….

  11. I do not often agree with the late G.E. Moore (I prefer Harold Prichard and Sir William David Ross – but they are less well known now) – but about Idealism he was basically correct.

    One does not need big things, such as Iceland, to disprove (although “disprove” is the wrong word – as the burden-of-proof is actually in the Idealist) Idealism – small things, such as a human hand, will do.

    If I stop “perceiving” my hand (if I look away) does it no longer exist? Of course it does not.

    Say there is a spot on my back which neither I (nor anyone else) has ever seen.

    Does this mean the spot on my back does not exist till I (or someone else) sees it? Of course not.

    And if “modern physics” says different then “modern physics” is tosh.

    Ditto with any claim that the “I” (the reasoning agent – real choice) does not exist.

    As such a claim is self refuting – as the person who makes such a claim is denying their own self (their own agency – their “I”), they are denying they are persons. A self denying the existence of the self.

    It is just wrong – as saying “A is not A” is wrong.

  12. There is a general point that needs to be made – not especially about this post, but about many posts on this site (about many subjects).

    If one thinks that modern Britain is not well governed (thinks that we have declined in the sense that we are now massively over governed – that the state is vastly too big) then it does not make sense to follow the thinkers who got us here.

    The establishment have NOT interpreted the various thinkers on the Oxford PPE course (Hobbes, J.S. Mill and so on) in an extreme – if anything they have interpreted them in a moderate way (Mr Clegg and Mr Cameron and so on deserve their Firsts, they repeated back, to the letter, what they were taught – they are “liberals” in the sense that someone like T.H. Green was a “liberal”).

    It is not sensible to demand the limited government of the Old Whigs (and even of Tory folk such as Dr Johnson) and to embrace the philosophy of their enemies.

    One can not (consistently) demand limited government – and take your ideas from Thomas Hobbes.

    Nor can one (consistently) defend private landownership against the demands of the state – and take your ideas from J.S. Mill (or James Mill come to that).

    One can not (consistently) denounce bureaucracy – and take your ideas from Jeremy Bentham.

    And on and on………

    It one embraces the philosophers of the modern establishment it is not consistent to then turn round and denounce the politics of the modern establishment.

    The former leads to the latter.

    It is like praising Rousseau and then demanding individual rights against the “General Will” as expressed by the Lawgiver.

    Sorry my dears – but this will not work.

    I repeat that this comment is a general one – about quite a lot on the site.

  13. I like Samuel Johnson’s view on this. Boswell’s Life of Dr Johnson has this:

    After we came out of the church, we stood talking for some time together of Bishop Berkeley’s ingenious sophistry to prove the nonexistence of matter, and that every thing in the universe is merely ideal. I observed, that though we are satisfied his doctrine is not true, it is impossible to refute it. I never shall forget the alacrity with which Johnson answered, striking his foot with mighty force against a large stone, till he rebounded from it — “I refute it thus.”

  14. Sorry, haven’t read the whole thread. But the short answer to the headline is, “yes, but you can’t prove it logically”. In practise, this means you live your life on the assumptions that it is real, and the things in it are real, and other people are real and so on, but with the proviso that you might be wrong in particular instances. Which is what I get from David Hume, basically.

    There are no facts that can be declared 100% certain, but you have to assume that some are in order to function. Reality is messy. The human mind does not contain the world (duh) but only contains impressions of it. Those impressions might be in error, so be prepared to consider that you’re wrong. That doesn’t mean you must deny the existence of anything, just the possibility that what you think you know isn’t correct and you should be prepared to change your belief in the face of sufficient evidence.

  15. I know that Paul is religious, which may lead some to conclude that he is not being logical, but as an atheist I have to point out that as far as Objectivism is concerned he is also correct.
    It is perfectly true that you cannot prove that reality exists independently of our awareness of it but the point is – you don’t have to. It is an axiom – it is a foundation of proof like free will and is implicit even in the denial of it.
    If there were no independent existence and no free will there would be no requirement for proof – we would all be stuck in the forest like animals but to understand how we differ from animals and how we got out of the forest we have to understand the nature of concepts and the fact that – contrary to Hume – concepts ARE NOT PERCEPTS.
    This is why Ayn Rand is so important – all this is very clear if you understand her “Introduction to Objectivist Epistemology” [ITOE.]
    So why doesn’t everyone agree with Ayn Rand if she is right and everyone else, including most scientists, are wrong.
    I think it does come down to this issue of direct v indirect realism. Rand is a direct realist – we don’t perceive impressions or the effects on our sense organs [or perceptions for that matter] – what we perceive is reality.
    This is not a new idea incidentally – it is as old as Socrates and it is one of the things that Plato got right but you have to dig for it a little – it is in the Thaetetus.
    To say that we “create” the contents of our mind is like saying we “create” the contents of our stomach – we do not. Yes we can process our food and we can, in a sense, regard our perceptions as processed but the food itself, like the perceptual realm, is a given.
    I think part of the common error concerning realism is due to the third person perspective – we observe someone else looking at a tree – and we see an image of an inverted tree on their retinas and we conclude that they see what we see – an image on their retinas.

    But that is not what they ‘see’ – they have nothing to ‘see’ their retinas with – what they see is reality and they see it directly.

    Another problem is Descartes himself – moderns unwittingly accept his most destructive and misleading assumptions even as they deny him, this is the great mistake that Hume made, which was accepted and subsequently enhanced to its most destructive form in Kant.

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