SelfAwarePatternsDoes reality require observers?
Amanda Gefter has an article at Nautilus a couple of you have asked me about: Reality Exists Without Observers? Boooo! The title is an accurate summary of her thesis. Gefter is responding to a book by Vlatko Vedral, where he reportedly argues for a reality that doesn’t require observers. In terms of quantum mechanics, Vedral is an Everettian, although he seems to downplay the many-worlds aspect, focusing on the physics. He touts what’s often taken to be an advantage of the interpretation over Copenhagen, that it doesn’t require any special role for the observer.
Gefter’s stance is that this can’t be done, that any attempt to do it inevitably sneaks the observer back in. She also implies that most discussions about Neils Bohr, Werner Heisenberg, and the other thinkers behind Copenhagen, strawman their positions. Since “the Copenhagen interpretation” is actually a diversity of views held by many early quantum scientists, she’s probably not entirely wrong. But arguing about what the Copenhagen interpretation is or isn’t strikes me as just as problematic.
Even if we restrict ourselves to just Bohr’s ideas, the man’s writings are infamously opaque. When trying to decipher his views, it seems possible to come away with a variety of ideas. When I’ve read about them, he comes across to me as an instrumentalist, although one who doesn’t want to admit it. Many science historians argue he was a Kantian, or maybe a neo-Kantian. Within the bounds of this discussion, I’m not sure how significant these distinctions are. What seems clear is he doesn’t take quantum theory to be telling us about reality, only our interactions with it.
When someone starts arguing for an observer centric reality, they can mean at least a couple of different things. One is epistemic, that our knowledge of reality only comes through observers. Bohr reportedly included non-conscious observers in this. But with that stipulation, the view doesn’t seem particularly radical. Another way of saying it is that all information must come through information gathering systems, which doesn’t sound nearly as profound.
But an observer centric reality can also be a stronger claim, an ontic one, that says conscious observers construct reality. The strongest claim of all is that reality doesn’t exist until we consciously observe it, that the observation itself brings it into existence. This is either idealist or solipsist territory.
It’s important to understand that even under the epistemic view, observation has effects on quantum systems. We can observe a supernova twelve million light years away without affecting it. Or we can observe the flow of a river without meaningfully affecting it. In these cases, there’s already enough interaction happening between the system and its environment that we can learn from the effects of those interactions that reach us.
However, we can’t observe a quantum system without interacting with it, and interaction entangles the observer and the observed, changing both. For the quantum system, that typically results in at least decoherence, and in many interpretations, all but one of the possible outcomes disappearing.
Which one of the above is Gefter claiming? I’m not sure, and that, unfortunately, is all too common when trying to parse arguments for this view. If forced to guess, I’d say she’s agnostic on the distinction, as this discussion about the moon seems to show.
Let’s put this moon thing to rest. It’s true. We can’t say the moon is there if no one’s observing it. Neither can we say that the moon’s not there if no one’s observing it. It’s not as if the sky is empty until someone gazes upward and a moon suddenly pops into existence. It’s that we can’t say anything about the moon as an independent object, because quantum theory doesn’t grant us independent objects, only measurements that we can slice into moons.
Not that Copenhagen is Gefter’s preferred interpretation. She actually favors QBism. Historically the name meant quantum Beysianism, in the sense that quantum theory provides degrees credence in various outcomes. It’s a view which focuses on the subjective experience of the experimenter. Or at least that’s how I understand it.
But again, the question becomes, is this just an epistemic view, or an ontic one? It seems to depend on which QBist you ask. On the one hand, it could be seen as a straight instrumentalist approach to quantum theory, a reification of the “Shut up and calculate!” attitude. Interestingly, the originator of that phrase, David Mermin (not Richard Feynman), signed on to QBism at some point.
Many QBist proponents resist the instrumentalist label. Which in turn often leads to accusations of solipsism, which they also resist. As I noted above, this starts to sound a lot like idealism to me, although it’s not clear that’s what they mean either. In the end, most physicists seem to regard QBism as an epistemic interpretation. (I’ve already done a post on why epistemic approaches don’t work for me.)
But what about the ontic view of an observer centric universe? If you already lean toward some form of ontological idealism, then this may well be a natural conclusion. But I don’t think there’s anything in the physics that drive it. A lot of this type of discussion seems to ignore the lessons from quantum computing, where engineers struggle with systems that decohere all the time, much earlier than they would prefer, and with nothing we’d normally call an “observer” driving it. (Unless we say the environment is the observer, but then “observer” seems to lose all distinctive meaning.)
If you think about it, this is no different from the classic double-slit experiment. If we put a polarizing filter at one of the slits, no conscious agent gets the information on which slit the particle goes through any sooner. What conscious agents do see is a change in the results on the back screen, and then infer what happened at the slits.
So the epistemic point about observers seems valid enough. I haven’t read Vedral at length, but I’d be surprised if he disagreed. But the ontic one doesn’t seem particularly well motivated, at least unless your metaphysics already push you in that direction.
But maybe I’m missing something? Is there an in-between ground between the options I listed? Or evidence for the ontic version I’m overlooking?
#consciousness #interpretationsOfQuantumMechanics #manyWorldsInterpretation #philosophy #physics #qbism #quantumMechanics #science
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