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To make a long story short, Bishop Berkeley argued that the idea of matter existing independently of perception was incoherent, since the properties of matter are (or were in Berkeley's time) defined in perceptual terms such as hardness, redness, etc. Hence, Berkeley's conclusion that "to be is to be perceived."

Of course, Berkeley knew that there is a world beyond human perception, but since he argues that being is being perceived, he concluded that there is a Great Perceiver, God, responsible for what we call the external world.

Thus, Berkeley's argument addresses two major philosophical issues: the problem of the thing in itself (solution: there is none) and the existence of God (there must be one in order for the external world to exist).

However, modern physics has led to a description of matter that--it seems to me--need not reference perceptual properties at all. In fact, matter has properties that not only lie beyond our perception, but literally can't be imagined in perceptual terms--mass, charge, "charm," "strangeness," (the latter two being names for properties of subatomic particles), and more.

Has physics thus undermined Berkeley's idealism, or has it merely prompted refinements in the arguments of the few modern idealists?

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4 Answers 4


These things you write which "can't be imagined in perceptual terms", as Rex Kerr points out, must also be observable, even if we can't observe them with our current technology. The point is that they are based on experience, and whether seen through a microscope or calculated to exist by crunching numbers, the properties are theoretically observable, and that's all that matters. The crux of idealism can't be undermined by anything we can observe or theoretically observe.

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But the crux is a logically invalid step, as described by the OP (and Berkeley); is it a meaningful statement to say that invalid reasoning is "not undermined"? Less radical (and not trivially flawed) idealism is also probably untouched, but a little more explanation of which strains of idealist thought are both logically plausible and invulnerable to this kind of observation would make this a better answer. –  Rex Kerr Apr 9 '12 at 16:32
It is, I agree, and I even voted up your answer before I posted mine so people would be sure to read it. :-) But I did not include it in mine because it is outside the scope of the question, which merely asks whether modern physics undermines Berkeley's idealism, not whether Berkeley's idealism is based on a false assumption. That, and you already said it; I only posted my answer because I felt the need to emphasize that observable things can't undermine subjective idealism. –  stoicfury Apr 9 '12 at 19:40
The details of your point were not quite clear to me before, but now I think I understand what you were conveying. Something like: all central conclusions of idealism are obtained only by noting that all concrete knowledge of the world is ultimately dependent upon perception, not on what the content of the perception is. (Therefore, observable things can't undermine subjective idealism.) If that is what you were stating, then I agree with the logic, and am not sufficiently familiar with modern idealism to know whether I agree with the characterization of it. –  Rex Kerr Apr 9 '12 at 20:12
Your emphasis on the word "that" is confusing to me (so I hope I'm not reading it wrong), but yes, the content of perceptions is irrelevant; Berkeley's idealism is just phenomenalism + classic idealism. I'm not sure what would be defined as "modern idealism" these days, as very few people are actually idealists, thanks to Kant and others. –  stoicfury Apr 9 '12 at 21:13
I meant to emphasize "only". I wonder how that happened? Anyway, I believe we are in agreement. –  Rex Kerr Apr 9 '12 at 21:34

I agree with stoicfury. But I think there is an additional argument that the crux of idealism can't be undermined in the way you propose (whatever may be the weaknesses of Berkeley's version of idealism), even beyond the idea that everything is "theoretically observable".

In the case of "matter (with) properties beyond our perception" there is still a very concrete, untheoretical chain of perception between the so-called object and our experience of it. That might be a long, complex series including observations of readings on instruments, data on computer screens, and so on. There may (must?) also be inferential links in the chain.

But nothing in such a chain is fundamentally different than so-called ordinary perception. Yes, we use artificial instruments and complex apparatus to generate the ultimate perceptions of the "objects" of physics such as subatomic particles and waves, but how's that different in kind than, say, the apparatus of the eye and the visual pathways in the nervous system; or the use of natural or artificial light to make things visible; or the mediation of air to carry sound so we can perceive it; etc.

The trickiest part of that might be the use of inference to "see" the properties of objects such as mass, charm etc. But even in ordinary perception there have to be mental processes involved, a kind of instant inference, to "see" a fully formed object when all we really get from the "outside world" is raw sense data, with no actual object. Yet we "see" a whole tree all but instantaneously.

And often we need higher-level mental processes, a kind of inference, to "see" objects that are ordinarily familiar. I doubt if a primitive tribesman could look at, say, a cell phone and "see" anything near what we instantly perceive when one comes into view. And in fact, on first glimpse, from an unusual angle, partly obscured or under reduced light, even we might not "see" a cell phone where one is present. But as we look harder and think about what we are looking at, and compare it to what we know about various objects, it might suddenly become apparent -- hey, that's a cell phone. Even further, everybody has certainly experienced looking at so-call objects and not being able to tell even where one object ends and another begins. (

As for the need for artificial instruments or the lack thereof, I keep a jeweler's magnifying eyepiece on my desk for looking at ultra-fine print and other tiny objects that occasionally cross my path. And even then I sometimes need to think hard to fill in obscured words or properties. I've occasionally even resorted to magnifying fine print and small images with a copier/scanner so I can "see" them better. So much for the unaided senses.

Actually, if anything, modern physics has, IMHO, strengthened the case for some sort of idealism. These properties of particles that we "see" -- "color", "charm" and "spin" -- have little or no actual basis in sense data or ordinary perception. They are -- sometimes whimsical -- metaphors for "properties" that are arguably largely mental in character. "Charm" is of course, a particularly good example. Arthur Eddington, the astrophysicist who first confirmed general relativity, was a major proponent of this view.

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+1 for a good summary and argument, though I disagree with your last point that the properties are "largely mental in character". They're simply regular in character. It's not particularly useful to associate a very simple regularity with the immense complexity of processing that goes along with mental processing in humans. Properties like friendly and whimsical and considered would IMO properly be called mental in character; quark flavor is, despite the name, just a six-value index into a (semi-regular) table of simple properties (one entry of which is titled "charm"). –  Rex Kerr Apr 9 '12 at 16:55
Thanks. I'd be grateful for references to others who have argued the "chain of perception" -- it's something I came to on my own. Not sure what you mean by "regular" properties. If material properties come down to numbers in a table, they are "mental" in some very strong sense ISTM. But one way or another, it seems hard to deny that 20-21st century physics has pretty thoroughly destroyed any naive notion of objects "out there" as we actually perceive them in everyday life, and IMHO that strengthens the overall case for some kind of idealism, or at least anti- or non-physicalism. –  David Lewis Apr 10 '12 at 2:11
I don't understand why a table lookup is mental in any interesting sense of the word "mental". Abstract, yes; regular, yes; but it can be implemented physically, and if it describes how the physical world works, I don't see a useful distinction. You may as well say that numbers are mental and therefore that I have ten fingers is a case for idealism, or that objects are mental constructs and therefore that there are atoms (tiny objects!) is a case for idealism. This seems to lead to exactly the sort of question-begging that made Berkeley's logic invalid. Do I misunderstand? –  Rex Kerr Apr 10 '12 at 14:39
The so-called "chain of perception" is a quite common notion in Indian Buddhism (although not necessarily by that name); very schematically, "to exist" is defined as "to have causal efficacy", and perception is viewed as causal (i.e., the cup causes my eye to see it.) In short: anything incapable of causing (directly or indirectly) a perception simply doesn't exist. –  Michael Dorfman Apr 12 '12 at 13:27
Right... and in both Buddhism and Hinduism, inference is a pramana, a mode of knowledge, parallel to the senses, whose objects are abstract truths that we "see" with inference. Hey, it's even in everyday language -- "yes, I see the point", "I see trouble ahead", "Let's see if this will work as designed", etc. –  David Lewis Apr 14 '12 at 3:21

Quantum mechanics goes a lot further than what is often represented. It implies that there might not be properties at all (no reality, as we know it), independent of a measurement event. The measurement event is not just a physical interaction (that results in just another entangled state).

Einstein, Podolsky and Rosen (EPR) wrote a paper that came to be known as the EPR paradox. It was based on a thought experiment around the entanglement, separation and then measurement of a property of a pair of particles. EPR pointed out that the theory implied that a measurement on one particle had an instantaneous effect on the distant particle. Einstein argued that god does not play dice or use telepathic methods... his argument was that there must be something wrong with quantum theory, as it seemed to imply that one has to give up either or both 1. reality or 2. locality. That can't be right, they argued.

So quantum theory, it was suggested, must be incomplete. It mustn't contain all the variables. There must be some hidden variables that explained how there seemed to be instantaneous action at a distance or non reality. These "hidden variable" theories were first tested with John Bell's theorem (Bell inequalities) . Using entangled pairs of spin 1/2 particles, Bell devised an experiment. By measuring the spin on these entangled pairs of particles at varying angles, the hidden variable theories predicted a different statistical outcome than the quantum mechanical theories. Numerous experiments appear to confirm quantum mechanics.

Consensus has been to preserve reality, but lean towards entanglement.. that faster than light influence is possible. But something else I read today suggests a more recent theorem and corresponding experiments which implies that the assumption of reality is problematic as well. Physicsworld.com cites the journal Nature as the source for the statement:

..reality does not exist when we are not observing it.

But "reality" here is meant as the kind of reality we can understand - the reality of observables. Physics does postulate that something behind that might be said to "exist" - the wavefunction. But the use of the word "exist" in this context is problematic. I mean, we can kind of conceptualise Schrodinger's cat... but that's not supposed to teach us about cats, but rather get us thinking about the kind of thing the cat is entangled with. What is it? We cant seem to ascribe reality to it.

And at that point, I think it's kind of wide open. You could think of it as Kant's noumenon. Might as well say it's calculations in the mind of god. Or you can just leave it as the wavefunction. Could even call it nothing. It's all equally non-sense, in a way.

So I think modern physics can be seen to reinforce Berkeley's idealism, not undermine it. Where Newtonian physics seemed to close a lot of doors, quantum physics seems to open them.... and at those extremities, one is so lost.. the choice of how to view existence seems more an aesthetic choice than a scientific one... and maybe an aesthetic choice at the boundaries can be said to be a religious one.

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While one can argue that the successes of particle physics and cosmology demonstrate that we can make reliable predictions about the world with only very indirectly invoking perception, this observation is intrinsically no different than realizing that a tree can fall in the forest without being observed. Berkeley's argument would remain the same: although we do not / cannot perceive atomic spin, the Great Perceiver can. If you buy Berkeley's arguments pre-modern-physics, you should buy them now, also. The logical structure is unchanged.

However, I think this highlights why various criticisms of Berkeley are and have been on target (Wikipedia summarizes some of the most important). In particular, even if you define the properties of matter on the basis of perceptual qualities, unless your definition creates the matter, the future behavior of that matter is not constrained by how you try to describe it. Postulating a being whose definitions do create matter is, then, obviously just cheating (though you can construct a circular argument with which to confuse yourself about the unjustified step).

So Berkeley-style idealism never had a sound basis, and modern physics just emphasizes that.

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