Here is how I interpret your claim here: The only way the Copenhagen interpretation could be an absolute state theory - i.e. a theory where the quantum state of a system is absolute, not relative to some other system - is for collapse to be caused by conscious agents. Am I misinterpreting you?
If I'm not, I don't see why you believe this. The Copenhagen interpretation does say that a certain class of interactions - measurement interactions - produce collapse. And I acknowledge that it cannot maintain that all physical interactions are measurement interactions. That view has been conclusively refuted empirically. However, why think that the only alternative is that measurement interactions must involve conscious observation? Bohr, as far as I can tell from his mysterious proclamations on the topic, seemed to think that any interaction with a macroscopic system is a measurement interaction. He didn't think that consciousness played any essential role in his interpretation. I think Wigner was the one who emphasized consciousness.
Now you could say that Bohr's interpretation is untenable, since microscopic/macroscopic is a continuum, not a binary distinction. Also, macroscopic systems are just built out of microscopic systems, so why think the measurement problem doesn't apply to them? I agree! But the exact same criticisms can be raised about consciousness, so Wigner's interpretation is not on sounder footing here. So I guess I'm not seeing why you think a Wigner-type delineation of measurement interactions is the only way to avoid Copenhagen collapsing into Everett.
Here is how I interpret your claim here: The only way the Copenhagen interpretation could be an absolute state theory - i.e. a theory where the quantum state of a system is absolute, not relative to some other system - is for collapse to be caused by conscious agents. Am I misinterpreting you?
You got it! Thank you!
...If I'm not, I don't see why you believe this. The Copenhagen interpretation does say that a certain class of interactions - measurement interactions - produce collapse. And I acknowledge that it cannot maintain that all physical interaction
Suppose you believe in the Copenhagen interpretation of quantum mechanics. Schroedinger puts his cat in a box, with a device that has a 50% chance of releasing a deathly poisonous gas. He will then open the box, and observe a live or dead cat, collapsing that waveform.
But Schroedinger's cat is lazy, and spends most of its time sleeping. Schroedinger is a pessimist, or else an optimist who hates cats; and so he mistakes a sleeping cat for a dead cat with probability P(M) > 0, but never mistakes a dead cat for a living cat.
So if the cat is dead with probability P(D) >= .5, Schroedinger observes a dead cat with probability P(D) + P(M)(1-P(D)).
If observing a dead cat causes the waveform to collapse such that the cat is dead, then P(D) = P(D) + P(M)(1-P(D)). This is possible only if P(D) = 1.
If you don't say that only conscious agents can collapse waveforms, then you have to agree that something in the box collapses the waveform as seen from inside the box, while it's still uncollapsed to Schroedinger. And Schroedinger's opening the box collapses that waveform for him; but it is still uncollapsed for someone outside the room. This seems like it might be equivalent to many worlds - all possibilities already exist; you just haven't chosen which one you're going to access until you open the box.
But if you do say that only conscious agents can collapse waveforms, then it's something about their mental processes that does the collapsing. This could mean their beliefs matter. And then, the cat is always dead.
ADDED: People. Read the entire post before responding. I am not claiming that the cat is always dead. I am not claiming that consciousness collapses waveforms. I am claiming that there are only 2 known alternatives:
If you can't produce another alternative, and you don't believe in many-worlds, you owe me an upvote.
Finally, this post is supposed to be fun! You are crushing all whimsy and playfulness on LessWrong when you pile downvotes like bricks on anything playful because it does not provide a complete and satisfactory resolution.