Difficulties over probability have often been considered fatal to the Everett interpretation of quantum mechanics. Here I argue that the Everettian can have everything she needs from `probability' without recourse to indeterminism, ignorance, primitive identity over time or subjective uncertainty: all she needs is a particular *rationality principle*. The decision-theoretic approach recently developed by Deutsch and Wallace claims to provide just such a principle. But, according to Wallace, decision theory is itself applicable only if the correct attitude to a future (...) Everettian measurement outcome is subjective uncertainty. I argue that subjective uncertainty is not to be had, but I offer an alternative interpretation that enables the Everettian to live without uncertainty: we can justify Everettian decision theory on the basis that an Everettian should *care about* all her future branches. The probabilities appearing in the decision-theoretic representation theorem can then be interpreted as the degrees to which the rational agent cares about each future branch. This reinterpretation, however, reduces the intuitive plausibility of one of the Deutsch -Wallace axioms. (shrink)

Jeffrey Barrett presents the most comprehensive study yet of a problem that has puzzled physicists and philosophers since the 1930s.

In a revolutionary new book, a theoretical physicist attacks the foundations of modern scientific theory, including the notion of time, as he shares evidence of ...

"A leading scientist interweaves evolution, theoretical physics, and computer science to offer a new understanding of reality"--Cover.

An extraordinary and challenging synthesis of ideas uniting Quantum Theory, and the theories of Computation, Knowledge and Evolution, Deutsch's extraordinary book explores the deep connections between these strands which reveal the fabric ...

As shown in The Quantum Mechanical Frame of Reference, Everett's formulation inherently defines idiosyncratic effective physical environments for each version of the functional identity of the observer, defined solely by observations, in the manner of Rovelli's Relational Quantum Mechanics. This accounts for determinate measurement records, and completes his resolution of the measurement problem. The remaining task is to make everyday sense of Everett's concept. He defines the functional identity as the record of sensory observations and machine configuration, which seems merely (...) an epiphenomenon of the body-mind of the observer. This functional identity is intensely familiar to each observer. It is simply the subjective reality, the known world, here the 'world hologram'. In Everett's formulation, the cut in the von Neumann chain is implicitly made at the level of conscious sensory awareness. Thus, not only is the effective physical environment defined solely by the record of observations, the self-identity synthesised from observations defines the sole determinacy of the body-mind of the observer. Everett's formulation is not addressing obscure issues of brain state, but the determinant of the effective physical reality of the observer, including the body-mind. Although highly counter-intuitive, it is nonetheless empirically coherent. On the 'inside view', as defined by Tegmark, Everett's relative state corresponds, directly and precisely, to human experience. (shrink)

Relational quantum mechanics is an interpretation of quantum theory which discards the notions of absolute state of a system, absolute value of its physical quantities, or absolute event. The theory describes only the way systems affect each other in the course of physical interactions. State and physical quantities refer always to the interaction, or the relation, between two systems. Nevertheless, the theory is assumed to be complete. The physical content of quantum theory is understood as expressing the net of relations (...) connecting all different physical systems. (shrink)

Everett's relative-state formulation of quantum mechanics is an attempt to solve the measurement problem by dropping the collapse dynamics from the standard von Neumann-Dirac theory of quantum mechanics. The main problem with Everett's theory is that it is not at all clear how it is supposed to work. In particular, while it is clear that he wanted to explain why we get determinate measurement results in the context of his theory, it is unclear how he intended to do this. There (...) have been many attempts to reconstruct Everett's no-collapse theory in order to account for the apparent determinateness of measurement outcomes. These attempts have led to such formulations of quantum mechanics as the many-worlds, many-minds, many-histories, and relative-fact theories. Each of these captures part of what Everett claimed for his theory, but each also encounters problems. (shrink)

Everett demonstrates the appearance of collapse, within the context of the unitary linear dynamics. However, he does not state clearly how observers are to have determinate measurement records, hence 50 years of debate. This, however, is inherent. He defines the observer as the record of observations, which, naturally, is the record of correlations established with the physical environment. As in Rovelli's Relational Quantum Mechanics, the correlations record is the sole determinant of the effective physical environment, here the quantum mechanical frame (...) of reference: due to multiple realisation of the functional identity of the observer, the physical environment is a simultaneity of all the physical environments in which it is instantiated, a 'universe superposition', in which only the environment correlated with the observer by observations is determinate. This effects a discrete and idiosyncratic physical environment for each version of an observer, in which determinate measurement records are recorded. Quantum mechanics is on this view fully relational, demonstrated as not only viable but necessary by Rovelli & Laudisa. The quantum mechanical frame of reference is Everett's 'Relative State', and on Tegmark's 'inside view', the time evolution follows the standard von Neumann-Dirac formulation. Thus observers get precisely the measurement records predicted by the standard formulation, but since objectively there is only the appearance of collapse, there is neither a measurement problem nor a disparity with relativity. The linear dynamics and the collapse dynamics are directly experienced, as the passage of time and the making of observations, respectively. (shrink)

Barbour shows that time does not exist in the physical world, and similar conclusions are reached by others such as Deutsch, Davies and Woodward. Every possible configuration of a physical environment simply exists in the universe. The system is objectively static. Observation, however, is an inherently transtemporal phenomenon, involving actual or effective change of the configuration, collapse. Since, in a static environment, all possible configurations exist, transtemporal reality is of the logical type of a movie. The frame of a movie (...) film is of one logical type, an element of a set of frames, the movie, itself of a second logical type. In a static no-collapse universe, the configurations are of the first logical type, transtemporal reality of the second. To run, the movie requires iteration, a third logical type. Phenomenal consciousness is subjectively experienced as of this third logical type with regard to physical configurations. Everett's formulation clearly describes the transtemporal reality of an observer, which follows the physical in the linear dynamics, but departs from it on observation, giving rise to the the appearance of collapse, and the alternation of dynamics defined in the standard von Neumann-Dirac formulation. Since there is no physical collapse, his formulation is disputed. Given an iterator of the third logical type, the appearance of collapse is simply evidence of iteration. Chalmers demonstrates that phenomenal consciousness is of this logical type, an emergent property of the unitary system as a whole. Given an iterative function of this nature, one contextual to the physical configurations, paradoxes of time are resolved. Subjectively, meaning from the perspective of the iterative process, time passes in an objectively static universe, and the appearance of collapse is effected. (shrink)

We are reviewing and summarizing evidence for the processes of acquisition of information outside of conscious awareness (processing information about covariations, nonconscious indirect and interactive inferences, self-perpetuation of procedural knowledge). A considerable amount of data indicates that as compared to consciously controlled cognition, the nonconscious information-acquisition processes are not only much faster but also structurally more sophisticated in the sense that they are capable of efficient processing of multidimensional and interactive relations between variables. Those mechanisms of nonconscious acquisition of information (...) provide a major channel for the development of procedural knowledge which is indispensable for such important aspects of cognitive functioning as encoding and interpretation of stimuli and the triggering emotional reactions. (shrink)