[Paper Review] Why am I me? and why is my world so classical?

Anthony Sudbery|ArXiv.org|Nov 20, 2000

Paranormal Experiences and Beliefs15 references3 citations

TL;DR

This paper applies Nagel's distinction between internal (first-person) and external (third-person) perspectives to resolve the measurement problem in quantum mechanics. It proposes that the projection postulate is not a physical law but a statement about conscious experience, reconciling unitary evolution with probabilistic outcomes via a contextualized, empirically realist interpretation of Everett's relative-state formulation.

ABSTRACT

This is an attempt to apply Nagel's distinction between internal and external statements to the interpretation of quantum mechanics. I propose that this distinction resolves the contradiction between unitary evolution and the projection postulate. I also propose a more empirically realistic version of the projection postulate. The result is a version of Everett's relative-state interpretation, including a proposal for how probabilities are to be understood. Based on a talk given at the 9th UK Foundations of Physics meeting in Birmingham on 12 September 2000.

Motivation & Objective

• To resolve the contradiction between unitary quantum evolution and the projection postulate using Nagel's internal vs. external perspective distinction.
• To provide a more empirically realistic interpretation of the projection postulate, treating it as a statement about conscious experience rather than a physical collapse.
• To reinterpret the Everettian 'many worlds' interpretation as a single world with multiple possible experiences, avoiding metaphysical proliferation.
• To explain how probabilities in quantum mechanics arise from the internal perspective of a conscious observer within a unitary framework.
• To draw analogies between the measurement problem and classical philosophical problems (e.g., 'Why am I me?') to suggest a unified conceptual resolution.

Proposed method

• Distinguish between external statements (descriptions of the universe's state vector evolving unitarily via the Schrödinger equation) and internal statements (experiences of conscious observers at specific times).
• Define a 'perspective' in a quantum system as consisting of: (a) a conscious system, (b) a specific time, and (c) an eigenstate of experience.
• Treat the projection postulate not as a dynamical law but as a statement about the stochastic transition of conscious experience, governed by Born rule probabilities.
• Reject the idea of 'many minds' or 'many worlds' as separate entities; instead, interpret orthogonal components of the state vector as possible experiences within a single world.
• Use decoherent histories and Simon Saunders' framework to contextualize the reality of measurement outcomes within specific observer perspectives.
• Apply the analogy between temporal flow, consciousness, and quantum outcomes to argue that questions like 'Why is it now?' or 'Why am I me?' are metaphysically on par with 'Why this outcome in a quantum measurement?'

Experimental results

Research questions

• RQ1 How can the apparent contradiction between unitary evolution and the projection postulate be resolved without abandoning either?
• RQ2 What is the role of conscious experience in interpreting quantum measurement outcomes, and how does it differ from a physical collapse?
• RQ3 Why do we perceive a single definite outcome in a quantum measurement when the state vector remains in superposition?
• RQ4 How does the distinction between internal and external perspectives clarify the nature of probability in quantum mechanics?
• RQ5 Can philosophical puzzles like 'Why am I me?' or 'Why does time flow?' be resolved using the same conceptual framework as the quantum measurement problem?

Key findings

• The projection postulate is not a physical law but a statement about the internal experience of a conscious observer, not a dynamical collapse of the state vector.
• The state vector evolves unitarily according to the Schrödinger equation, and the appearance of collapse arises from the perspective of an internal observer.
• There is only one world and one mind per observer; the multiplicity of outcomes corresponds to possible experiences, not separate minds or worlds.
• The reality of a measurement outcome is contextual: it is objectively true from the internal perspective of the observer, even though it is only one component of a superposition from an external view.
• The Born rule probabilities emerge naturally from the stochastic transition of conscious experience, not from a fundamental indeterminism in the state vector.
• Philosophical puzzles such as 'Why am I me?' or 'Why is it now?' are not answerable in the same way as physical questions, and their unanswerability is analogous to the unanswerability of 'Why this outcome in a quantum measurement?'