Re “Reality in Physics” by Richard Schlegel

C. A. Hooker

W. F. G. Swann

Robert K. Clifton

A. J. Leggett

Richard Schlegel 1981 London: University of Chicago Press viii + 302 pp price £13.50 This is not a textbook but a fairly ambitious attempt to reinterpret part of the foundations of special relativity and quantum mechanics, with some comments on the implications of this for more general philosophical issues. The two main innovations are: (a) the ‘interaction hypothesis’ – moving clocks do not physically run slow, but the well-known time dilation effects observed in (e.g.) muon decay are due to the interaction of the decay products with measuring instruments moving with respect to them; (b) the ‘restricted superposition hypothesis’ – only those states can enter a quantum-mechanical superposition that are related by a certain restricted set of symmetry operations.

Bernard d’Espagnat, Translated by J. C. Whitehouse

Jincheng Zhang

If Richard Feynman's path integral formulation had been proposed not merely as a computational tool for probability amplitudes, but as a fundamental physical ontology—namely, that "all histories collectively constitute reality"—the foundational paradigm of physics would have undergone a profound transformation. Traditional physics treats a single trajectory of a system in spacetime as the primary object and path integration as a summation technique over possible paths. This paper systematically develops an alternative framework: Physics of History Space, where the ensemble of all possible histories serves as the irreduceable primary object of physical description. Within this paradigm, physical reality is defined by the topology, measure, and algebraic structures over the space of histories, rather than being restricted to a single actualized trajectory. We establish the mathematical formulation of history space and re-examine the measurement problem in quantum mechanics, the problem of initial conditions in cosmology, and the philosophy of time. We demonstrate that classical single-trajectory spacetime emerges merely as a low-dimensional projection of history space under decoherence and stationary phase limits.