According to George Berkeley’s subjective idealism, everything in the universe is either a mind or an idea in the mind, and matter cannot possibly exist.
You’re reading these words on the screen of a particular device. You might be holding the device in your hand, or it might be resting on your lap, a desk, or some other convenient surface. Regardless of the exact model and set up of your device, there’s one thing that’s so obvious about it that it hardly needs to be stated: your device exists independently of you, as a lump of matter out there in the world.
…or does it? 18th-century Irish philosopher George Berkeley would argue that, in fact, the device you perceive exists only as an idea in your mind.
This might seem absurd, but the funny thing about Berkeley’s view is how, when you inspect it further, it can be difficult to really identify why it’s absurd.
Think about it. Your device has a certain color, size, and shape, which you perceive with your eyes. Close your eyes, and the device disappears.
No bother, you might think: you can still touch the device to know it’s there. Well, take away your sense of touch, and you’ll no longer feel the device’s presence.
Perhaps you can hear occasional notification bleeps. Take away your hearing, and those bleeps go too.
You might get desperate and try to smell or even taste the device, but if we remove those sensory capabilities, then even those emergency routes prove inadequate in providing a basis for the device’s existence.
The device you know and love has been reduced to a colorless, soundless, odorless, tasteless nothingness: there's no sign of the independent lump of matter that common sense initially presumed to exist. It turns out all we ever had access to were our own sensory perceptions, located in our mind. Take those away, and what’s left of the device’s existence?
The question we're really asking: remove conscious minds — remove our sensory perceptions — and what remains of the universe?
Reflections like those above led Berkeley to famously declare esse est percipi: to be is to be perceived. This slogan refers to the idea that it is being perceived that gives things existence, and encapsulates Berkeley’s view that minds and their ideas are thus the only things that exist, a view known as subjective idealism. As he clarifies in his brilliant 1710 work, A Treatise Concerning the Principles of Human Knowledge:
There was an odor, that is, it was smelled; there was a sound, that is, it was heard; a color or figure, and it was perceived by sight or touch. This is all that I can understand by these and the like expressions. For as to what is said of the absolute existence of unthinking things without any relation to their being perceived, that seems perfectly unintelligible. Their esse is percipi, nor is it possible they should have any existence, out of the minds of thinking things which perceive them.
You might think: well, take away my sensory perceptions, and of course I won’t be able to detect the existence of anything. This tells us nothing about the status of the world or the objects contained within it, for even if I am no longer able to perceive my device, that doesn’t mean my device has stopped existing. Someone else could perceive it if they were in its presence.
Well, Berkeley would agree. To be is to be perceived. So, if someone else was in the presence of your device, the device would then exist in the mind of that person. But take away the mind of that person, and again — what remains? As Berkeley states:
It is indeed an opinion strangely prevailing amongst people that houses, mountains, rivers, and in a word all sensible objects, have an existence natural or real, distinct from their being perceived by the understanding… for what are the forementioned objects but things we perceive by sense? And what do we perceive besides our own ideas or sensations? And is it not plainly repugnant that any one of these or any combination of them should exist unperceived?
The world we tend to think of as existing independently of us, Berkeley points out, is a world of sensory perceptions: a world of colors, smells, textures, tastes, and sounds. Ice cream on a summer’s day. A fire crackling during the night. A rainstorm soaking you to the bone. These sensory experiences may be real and vivid — but they remain sensory experiences, dependent on our sensory apparatus, existent only in the minds of those experiencing them. Where is the mind-independent stuff?
We might object by appealing to the fact that it’s perfectly possible to imagine a scene existing — say, a mountain forest, or a faraway planet — without a conscious mind there to experience it. But, of course, in doing the imagining, we would then be the conscious mind experiencing it. As Berkeley comments:
When we do our utmost to conceive the existence of external bodies, we are all the while only contemplating our own ideas. But the mind, taking no notice of itself, is deluded to think it can and does conceive bodies existing unthought of or without the mind; though at the same time they are apprehended by, or exist in, itself.
It is impossible to imagine any object existing independently from a mind, Berkeley argues, because in the act of imagining it, we use our own minds. Be it a tree, river, or a subatomic particle: they are all ideas dependent on our minds.
Perhaps we might think Berkeley’s argument rests on a conflation between our perceptions of the world, and the world itself. And once we clear away that conflation, all of the strange unintuitive confusion arising from Berkeley’s points will go with it.
We might grant Berkeley that, if we were to suddenly be deprived of our senses, the world of our experience would vanish. But that doesn’t mean the world itself would stop existing. There would still be underlying ‘stuff’ that endures — i.e. there would still be matter, the stuff that causes our experiences in the first place — even without anyone there to perceive it.
So, our perceptions of the world might be mind-dependent, mental; but that doesn’t mean the world itself is mind-dependent.
But this view — reminiscent of that put forward by the great empiricist John Locke — is mistaken, Berkeley thinks.
Try to imagine a world without your mind, he implores. What would such a world be like? Are we even able to conceptualize it?
As we saw with your device at the beginning of this article, once we strip objects of our sensory perceptions, we are left with a colorless, soundless, odorless, tasteless nothingness.
So, without our minds, what exactly endures? Are materialists like Locke simply insisting that, as well as our rich sensory perceptions, there also exists this colorless, soundless, odorless, tasteless stuff that we aren’t even able to conceptualize? But what grounds are there for claiming this? What does matter, this inaccessible non-mental alien substance, really add here?
Besides, even if we did grant materialists their precious matter, Berkeley continues, they have absolutely no idea how it could possibly cause conscious, mental experiences within us. As matter is necessarily colorless, soundless, odorless, and tasteless, how could such a non-mental nothingness possibly cause or give rise to colors, sounds, odors, or tastes within our minds — when it itself possesses none of these things? Berkeley writes:
By their own confession, [materialists] are never the nearer knowing how our ideas are produced, since they own themselves unable to comprehend in what manner body can act upon spirit, or how it is possible it should imprint any idea in the mind.
As philosophers of consciousness continue to argue about today, we have no real idea how non-mental ‘stuff’ can possibly give rise to mental ‘stuff’. How can colorless, tasteless blocks of matter that apparently exist independently of our minds, cause vivid sensations of redness or the taste of watermelon within our minds?
Far simpler, Berkeley thinks, to just say our sensations are the only things that exist here. Why posit a non-mental substance like matter standing behind them? Matter adds unnecessary complexity into our picture of the universe for it introduces a needless substance dualism. As Berkeley summarizes:
The production of ideas or sensations in our minds can be no reason why we should suppose [the existence of] matter or corporeal substances, since that is acknowledged to remain equally inexplicable, with or without this supposition. If therefore it were possible for bodies to exist without the mind, to hold they do so must needs be a very precarious opinion; since it is to suppose, without any reason at all, that God has created innumerable beings that are entirely useless, and serve… no manner of purpose…
In describing our experiences of the world, we never truly encounter or directly access ‘matter’. We only ever access our perceptions. Our perceptions can be nothing ‘like’ matter, for matter (if it exists) is necessarily colorless, soundless, odorless, and tasteless. Positing matter’s existence thus tells us nothing about why we have the experiences that we do. So matter, Berkeley concludes, is ultimately empty — and we have nothing to gain from thinking this non-mental substance exists independently from our minds.
It might be thought that there’s a hole in Berkeley’s argument. Even if we concede that everything we experience is, by definition, in our own minds, and that everything in our minds is, again by definition, ‘mental’, that doesn’t explain where all this experience comes from. Is Berkeley arguing our minds spontaneously create everything we experience? But what about shared experiences?
Say you’re eating a meal with some friends. Presumably everyone sees the same or at least a similar set up, and shares similar experiences eating the food, and so on. Is Berkeley saying everyone’s mind is uniquely generating their own experience? That seems absurd, and a much simpler explanation would be that there is an independently existing table (made of matter) that everyone is independently experiencing with their own sensory apparatus.
Berkeley agrees that there is an independently existing table, but disagrees that its existence depends on some alien non-mental substance like matter. Non-mental things, Berkeley reminds us, do not have the power to cause ideas in us: only other ideas can do that. So, the source of all ideas — including the source of your shared experience of the table — must be another mind…
In fact, not only must the source of our experiences be another mind, Berkeley continues, it must be a mind superior to human minds, for...
the ideas of sense are more strong, lively, and distinct than those of the imagination; they have likewise a steadiness, order, and coherence, and are not excited at random, as those which are the effects of human wills often are, but in a regular train or series — the admirable connection whereof sufficiently testifies the wisdom and benevolence of its Author.
Here the brilliant audacity of Berkeley’s argument is truly revealed: the objects of experience exist independently from us not as lumps of matter, Berkeley argues, but as ideas in the mind of God:
...all the choir of heaven and furniture of the earth, in a word all those bodies which compose the mighty frame of the world, have not any subsistence without a mind; that their being is to be perceived or known; that consequently so long as they are not actually perceived by me, or do not exist in my mind or that of any other created spirit, they must either have no existence at all, or else subsist in the mind of some Eternal Spirit.
With a bold, beautiful appeal to simplicity, Berkeley thus denies matter and claims everything is ‘spirit’: everything in existence is either a mind or an idea in the mind, and the reason the world appears consistently and independently from our minds is because it exists in the divine mind of God.
Our kneejerk reaction to Berkeley’s audacious conception of the universe might be: but what about science? Doesn’t today’s scientific picture of the world show that we live in a shared world of matter, and that Berkeley’s philosophy is surely outdated nonsense?
Well, Berkeley would argue his picture is very much consistent with science. The Laws of Nature, revealed by scientific inquiry, indicate the order and structure of God’s mind. Subatomic particles are fundamental building blocks not of matter, but of God’s ideas and our own perceptions. Furthermore, one of 20th-century philosopher of science Karl Popper’s best-known papers is called A Note on Berkeley as Precursor of Mach and Einstein, and in it he shows how significant features of Berkeley’s philosophy are consistent with, and even implied by, modern physics.
However, though Berkeley is still widely read today, it must be admitted that his positive philosophy is not widely followed.
In his 1912 book The Problems of Philosophy, Bertrand Russell strongly critiques Berkeley’s view, claiming that Berkeley’s philosophy hinges on a conflation between what we mean by objects being ‘in’ the mind and ‘before’ the mind. Despite his belief that Berkeley’s philosophy is fallacious, Russell acknowledges its significance, writing:
Berkeley retains the merit of having shown that the existence of matter is capable of being denied without absurdity, and that if there are any things that exist independently of us they cannot be the immediate objects of our sensations.
Indeed, even if we don’t agree with Berkeley’s ultimate conclusions, anyone forming a conception of the world must take seriously his denial of matter, and recognize that the world of our sensory experience cannot possibly be ‘like’ the world as it exists without our minds, for the latter would necessarily be a world without color, sound, taste, or touch.
The objects of our sensory perception — your device, say — cannot possibly ‘resemble’ or ‘represent’ objects by themselves. Without a conscious mind there to perceive it, your device is something very different (an insight harnessed by Kant with his transcendental idealism). Berkeley thought it was so different, so alien and contradictory and empty, that there was no point entertaining its existence at all: its only ‘real’ existence is as an idea in your mind...
So, though we might balk at Berkeley’s positive picture, that does not reduce the power of his arguments against commonsensical conceptions of matter. He makes us question, what does ‘physical’ actually mean? What is matter? What is the boundary between perceiver and perceived? Is the world around us ‘real’? What is the universe like without conscious minds there to perceive it? And ultimately — what are the limits of human knowledge?
If you're interested in exploring these questions further, our introductory philosophy course, Life's Big Questions, discusses philosophy's best answers to the question of whether the world of our sensory experience aligns to ‘reality’, outlining René Descartes, John Locke, George Berkeley, David Hume, Immanuel Kant and many other great thinkers. Interested in learning more? Explore the full course now!
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