# Where exactly does Von Neumann say that consciousness causes collapse?

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It's often claimed that in Mathematical Foundations of Quantum Mechanics Von Neumann concluded that it's the observer's consciousness that collapses the wavefunction (Process 1).

But I am reading Chapter 6 of the book (both original and translation) word by word, and I don't find this conclusion. The closest is where he mentions the observer "abstract 'ego'" as one of the possible endpoints of the measurement chain (p. 421 in the 1955 translation).

This doesn't seem a "conclusion" to me. Is he more explicit elsewhere (in the same book or other writings)?

I think it was Wigner who made the implicit allusion by von Neumann explicit.

Of course, the reference to ego or consciousness or whatever else is placed at the end of the chain doesn't explain or resolve anything. It only moves the point of conflict to a different place.

Thanks @ArnoldNeumaier, this is my impression as well.

That's as far as Von Neumann went in the book: Von Neumann argued that the collapse of the wavefunction (Process 1) can be placed anywhere in a measurement chain, from the first measuring device to the observer's conscious perception of the measurement result. He implicitly suggested that the observer's consciousness ("his abstract 'ego'") could be where Process 1 happens, but didn't explicitly conclude that it is so. Stronger claims were then made by London and Bauer (The Theory of Observation in Quantum Mechanics) and Wigner (Remarks on the Mind-Body Question). Both essays are included in the "Quantum Theory and Measurement," edited by Wheeler and Zurek.

I made some remarks on how I think "Prcess 1" could occur in the "ego", if one takes a quantum mechanical description of all of reality (and thus the "many-worlds" scenario) seriously, in my answer to your question http://www.physicsoverflow.org/36063/given-decoherence-still-random-quantum-jumps-interpretations. Please tell me what you think of it. Best wishes!

Sorry, the answer below was meant to be a comment here. I'm new to this site :-)

Don't worry @DierkBormann, I have often posted an answer instead of a comment. See the other thread.

How can Process 1 "occur in the ego" if there is no Process 1? Decoherence seems to say that Process 1 is only apparent, an artifact of our separating the observed system from the rest of the world.

If we reinterpret Process 1 as the process that selects one of many possible outcomes in the mixture that results from decoherence, how does it work?

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