Reality is frequently inaccurate.
Douglas Adams, The Restaurant at the End of the Universe
If I'm lucky, you're already convinced, as a general principle, that what we call the 'physical world' is a complete fabrication of your mind (Quantum fans: here I still mean that independently of of quantum mechanics) If so, then yippee! You can skip to the section below on where I think quantum mechanics actually does fit in with this picture. That's the point of this post anyway.
If you're not convinced, then dang, I know I have my work cut our for me and will punt to a future posting. The philosophical perspective of idealism cuts so hard against the grain of our visceral intuition that it seems ridiculous, foolish and/or pointless to almost everyone at first. Grown men have been known to kick rocks in reaction to the notion, as the irascible Samuel Johnson did when he said of Bishop Berkeley's arguments "I refute him thus!"
Dr. Johnson's foot notwithstanding, idealism has a long and illustrious tradition that goes back to - you guessed it - at least as far as the Axial Age. The pre-socratic Anaxagoras (5th century BC) was the first Westerner we know of to tag his name to the notion (literally: he was known as nous - 'mind' because he taught that all comes from the mind). And of course if you're familiar at all with some Eastern philosophies like, say, Buddhism, you know many live and breathe idealism like a canary takes to song. Tons of big-wig philosophers and scientists - too many to name, really - have been strong proponents of some form of idealism. And really: at least some form of idealism clearly has to be true, if for no other reason than you're not an omniscient deity, but a brain-toting creature who has to make do with the limited data your neurons are serving up to your consciousness. But I think idealism can be broadened out and solidly defended much more than this - in a future post.
For now let me just be clear on what I'm not claiming. I'm not claiming this all could be some kind of dream and we'd never know the difference, like, say the movie Inception, or The Matrix. Some do argue in a scholarly context that we probably are living in a computer simulation. Personally, I think that particular argument fails because it just nonchalantly equates consciousness with computation, but that's for another post too. I'm not even going to argue that there is some kind of physical world out there, but we just have imperfect perception of it (e.g. Plato's cave or Kant's thing-in-itself).
What I claim (and, again, will argue for in a separate post) only sounds extreme, but once you get used to it, really isn't. I'm going assert that claiming any kind of 'real, physical world out there' independent of your mind is not only pointless, but actually meaningless. Meaningless like gibberish; like saying the square root of Tuesday is Jabberwocky. It might make you feel better to assert that it is so - and feel free to kick all the rocks you want - but really, it's a pretty incoherent claim.
So now let's say, or at least pretend, you're on board; i.e. you buy that to conceive of a reality beyond our mind's conceptual abilities is just mental mush (If not, well hell... the following still basically works, but has somewhat different implications). Then below is what I actually want to address.
Um... doesn't quantum mechanics already imply a type of idealism?
Quantum mechanics - at least in the version that bothered Einstein to his dying day - superficially makes a similar sounding claim. And even some physicists, I think, go a little overboard on this point. But in fact this particular ontological stance of quantum mechanics is of a different sort than what is generally considered 'philosophical idealism'. You may know the famous story of Einstein on a moonlight stroll with the physicist Abraham Pais. They were debating the meaning of the wave function collapse, and whether it meant that physical observables like position and momentum only existed by virtue of their measurement. Niels Bohr of course lead the majority answering in the affirmative. Einstein instead thought that most of his colleagues were nuts. At one point in the conversation, the great relativist turned in exasperation to his friend and asked him "Do you really believe the Moon is not there when you're not looking at it?"
What bugged Einstein was this: quantum theory in its no-frills form claims that Schroedinger's wave function alone contains all the information there is about a physical system. That's 'ALL' in capital letters. That's obviously a boatload of information about, say, an electron. But for all that information, the wave function is amazingly silent on things that make up our everyday conceptual apparatus, like: where the electron actually is at any given time. Or the where the Moon is for that matter. It only gives different probabilities for where an electron (or, again, the Moon) might be found if an observer bothers to ask the question. Again, that's all one gets with the wave function: weighted rolls of a dice, if one asks the question. Take all that at face value and it means the electron and the Moon have no position until an observer locates them somewhere. Einstein's position was: are you kidding me?
But we now know that nature is, in fact, not kidding. In still a later posting I'll get in to the weeds of what I think is maybe the greatest story in science - the discovery that our most basic intuition about reality, (the sense we are actually born with, as psychology experiments with newborns seem to show) is just plain wrong. Here I'll just recommend a classic and very accessible account of the whole story by David Mermin: Is the moon there when nobody looks? With that I'll just state the straightforward, intuitive interpretation of the last few decades of exquisitely delicate quantum experiments: if no one hears the tree falling in the woods, it don't make no sound(*).
But that's nevertheless different than saying that things don't exist at all until they are looked at or thought of by somebody. For that matter, quantum mechanics as a physical theory is happy to assume physical things exist independently of us thinking about them. It's just that some properties of things don't exist until we try to measure them. In principle, that doesn't have to be any more mysterious than saying an accused criminal at trial is neither innocent nor guilty until determined to be one or the other by a jury. To me, that situation is pretty straightforward to grasp if we start with a basic materialistic view of the world; i.e. if we assume that at least there are such things as real, flesh and blood accused criminals. And of course the real Moon.
Where it gets puzzling, to me at least, is when one already has the stance of idealism = nothing meaningfully exists until someone thinks about it. If that's so, isn't it just a trivial corollary that some properties don't exist until they are measured?
Clearly not - at least not in the quantum mechanical sense. Quantum theory doesn't claim everything is nonexistent until it's measured. It makes a clear distinction between some properties, like position which needs someone to measure it, and others, like electric charge, which aren't so encumbered. So what's going on? Why the one and not the other?
Suppose we ask the obverse question: if the world is a creation of my mind, in what way could it still make sense to at least pretend it exists independently of me? How could I consistently maintain the fiction to myself that some things are not a mental creation? I think there is only one answer. And I think it is precisely the gymnastics our minds constantly do. The secret sauce, I believe, is mathematical predictability.
Our brains evolved as prediction machines - or equivalently, data compression machines. That's their job, day in, day out. (In this narrative it doesn't matter whether you think brains are 'physical' or not, the argument is the same) Even infants are good at making predictions and compressing order out of their sensory deluged world. Object permanence is probably the earliest data compression tasks our brains make about the world. Babies 1-4 months will already track moving objects in their visual field, and at 4-8 months they know that a ball covered by a blanket hasn't magically disappeared.
The reason the notion of object permanence works at all is, of course, that we can make successful mathematical predictions about our sensory data. When an infant tracks a moving object, it's brain is making a successful prediction about it's visual field. Those successful predictions get rewarded with a shot of dopamine, and - shebang - the prediction circuitry is reinforced. Eventually the prediction circuits get so strong that they carry emotional valence. We viscerally insist that the ball is still under the blanket. Or that the Moon is there. That's why a good magician is always so compelling to watch, even when we know it's just trickery. The point is, with object permanence embedded in our minds, we don't have to see the ball to 'know' it's there - we feel confident in predicting that if we look for it, we'll find it.
Mathematical predictability, then, is the coin of our ontological realm if no direct sensory data is available to us. Makes sense, right? After all, if you can't trust math, what can you trust?
So now let's get back to the quantum world, where, say, an electron's position is not mathematically predictable. It's not that we just don't have the right tools, or the right prediction software in our minds. It is just absolutely plain flat out not predictable. This is a special kind of unpredictability, or randomness that is different than, say the randomness of the weather, or a roulette wheel, or the stock market. Weather, roulette and stocks have, in theory, some level of predictability. In principle, a computer big enough could eventually crack at least some of the code for what makes those things tick. They're not truly random, but pseudo-random.
Quantum events are, at least as far as the theory and experiments tell us, are truly, truly random. No computer algorithm could have anything on these guys. That means no mathematical rules of any kind are violated if the electron turns up here... or over there...or way over here... or wayyyyy over there... it makes no difference. The only possible conclusion is: the electron just aint anywhere in particular until you find it somewhere.
And in conclusion...
Let me try to tie this together into a really very cool conclusion about quantum mechanics and idealism. It's usually said that quantum mechanics has two weird things about it. Randomness and Unrealness. Einstein is often quoted as saying "God doesn't play dice with the universe." But what bugged him more than the randomness was the unrealness part. What I have just argued for is that, in the end, they are two sides of the same coin. True randomness implies unrealness. Unrealness requires randomness. That basic point holds, I believe, whether one is a philosophical idealist or not. But it seems a much better fit the context of idealism. If I were instead a materialist, I would be really bothered, like Einstein was, about how in the hell all that random/'immaterial stuff' got into an predictable/material world in the first place?
(*) I only said this is the straightforward interpretation. I'll address other interpretations in future posts.