On 11 Dec 2011, at 19:24, meekerdb wrote:

On 12/11/2011 8:33 AM, Bruno Marchal wrote:

On 11 Dec 2011, at 07:13, meekerdb wrote:

On 12/10/2011 3:50 AM, Bruno Marchal wrote:
Some say that the interference of particles "with themselves" in the two-slit experiment is amble evidence for these, but MWI does nothing to explain why we observe the particular universe that we do.

Comp explains this completely, by explaining why you cannot understand that you are the one ending in Washington instead as the one ending in Moscow. It explains contingencies by consistent extensions.

But then starting from Philadelphia instead of Brussels "you" should end up in Washington - since it is much more similar to Philadelphia.

That might indeed be the case if my consciousness supervene on a generalized brain including a city, which get an internal role in the computation leading to your state. But in that case you have to ask the doctor to do the awkward substitution at *that* level.

Yes, that goes back to my concern that the "right level" may include a large part of the universe.


Which is also related to the 323 argument.

I am not sure of this.

Quantum mechanics would say that we (our brains) are extensively entangled with the rest of the universe and, as Russell puts it, the 323 register may be active in the other Everett branches.

There are no reason for that. The 323 register is, or can be, classical. If the brain is a quantum computer, I will emulate it on a classical machine, and do the 323 reasoning again on that classical computer. Also, QM is not part of the comp assumption. So the reversal physics/ arithmetic does not rely on the truth of falsity of QM. QM can be used to test the consequence of comp, but not of the reversal reasoning.

The idea of substituting a mechanism for part (or all) of ones brain is only plausible because we live in an quasi-classical world

But comp concerns a classical machine, even in the case we have a quantum brain. Quantum computing does not violate Church thesis, so we can always find a classical level, so that we have to take into account all computations going through our state in the UD*.

In the W and M duplication experience, we assume that the brain is the usual biological one in the skull. All what will matter in the probabilities is the distinguishibility of the self-localization outcome after the duplication. IN QM terms, seeing Brussels, Washington, and Philadelphia are orthogonal state, and not part of the brain, or of the computation leading to the state before the multiplication.

I don't know what you mean by "seeing is not part of the brain". Seeing different things presumably correspond to orthogonal states of the brain.

Exactly, and "seeing" will connect an external input (W, M, spin up, etc.) with a brain state.

Of course Philadelphia is just an example. I could choose even closer continuations.

The point of the step 5 in the UD Argument consists in showing that comp refutes the notion (by Nozick) of closer continuer. The probabilities (or credibilities, ...) will bear on all numerical *identical* reconstitutions of the brain capable of differentiating when getting new inputs (like W or M). The thought experiments are just more awkward when using a very low level, and that's why I use the neuro classical comp for the first six steps. Then the seventh step, introducing the UD in the universe, shows that the level does not matter. If the level just exists, it will be accessed by the UD, or the (sigma_1) arithmetical truth.

Suppose you are just reconstituted in Brussels, where you started, as well as Moscow.

That's step 5. Except that in step 5 you are even not annihilated in Brussels. And even in that case you will have to say 1/2 (in case you agree with the 1/2 for the usual duplication WM.

Does this mean "your" consciousness remains in Brussels while in Moscow there is not-Bruno?

Only with a chance of 1/2. There will be also a chance 1/2 I feel ending up in Moscow. But this is correct only in the theoretical protocol which assume no other reconstitutions other than those in Brussels and Moscow.

In front of the (concrete or not) UD, your consciousness will do the selection at the right level. (Again like in the Quantum MW).

There is no selection in MWI - everything happens.

There is no selection either in the WM duplication experience, from a third person point of view. But there is a selection from a first person perspective. All reconstituted persons does live like there has been a selection from their first person perspectives. Likewise with a quantum superposition of an observer state. That's how Everett justifies the use of probability in the context of the deterministic universal wave.



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