We propose the principle, the law of statistical balance for basic physical observables, which specifies quantum statistical theory among all other statistical theories of measurements. It seems that this principle might play in quantum theory the role that is similar to the role of Einstein's relativity principle.
Quantum theory has created a fundamental change in our ideas as relativity theory had done before. But while relativity theory is essentially classical in its conceptions—it is in fact the culmination of classical physics—quantum mechanics is founded on some new principles. The quantum laws are very different in character from the laws we find in classical theory. In particular, quantum mechanics is a strictly statistical type of theory : from this arises the different conception of causality that marks the new outlook of modern physics. Classical theory describes the so-called macroscopic phenomena, that is, things and events which are more or less of the same size and kind as we find them in ordinary life; and so a description can be given in terms of concepts close to the ones we use in ordinary language. The language of quantum mechanics is based upon a duality principle ; and most of our ordinary language is equally dualistic.
The concept of measurement plays both a central and a problematic role in quantum mechanics. First of all, and unusually, the word ‘measurement’ figures in the fundamental axioms of quantum mechanics - in principle (3) of Chapter 2 for example - and in this quantum physics is quite unlike classical physics as a whole. For though a measurement made on a classical system naturally involves an interaction between the system and a measuring apparatus, there is nothing special according to classical physics about measurement interactions. Describing the measuring process is a straightforward problem of applied classical physics. The classical laws of motion do not break down during the measuring process. For example, suppose you observe a classical particle using light bounced off it. In the classical account you can make the disturbance on the observed system as small as you like and, ‘in principle', you can observe the system with arbitrary accuracy. ‘In principle’ - a favorite expression of the philosopher of physics - means what it always means in physics. The contrast is with ‘in practice'. Of course, in practice there are all sorts of limitations on measurement. There are also some theoretical limitations, like those due to thermodynamics. But these are not the limitations imposed by the theory we are considering, namely classical mechanics. Such limitations as there are are imposed by some other theory. (The expression ‘in principle’ tends to be used when we are discussing the principles of a particular theory and, theoretically but not in practice, physics is a collection of disjoint theories.)
The premise that physical variables must be viewed as random variables, with observed values, assigned as averages over distributions, is shown to yield the formalisms of thermodynamics, Hamiltonian mechanics, and quantum theory. A general mathematical argument first establishes the validity of an embedding of th space of physical variables in a larger manifold of "hidden" variables and a general structure for the distribution of these variables. Then, by consideration of various ways of specifying the preparation of a system for measurement, the formalisms of physics cited above are deduced. It is also shown that the generalized Langevin equation follows from these premises and is applicable to a wide class of phenomena. This formulation yields a new definition for compatible observables as used in quantum theory and demonstrates, in a natural way, that physical laws should be invariant under orthogonal transformations of certain variables, which in one circumstance include the complex orthogonal transformations of the Lorentz form, as in special relativity. In summary, it appears that most of the formal structure of physical theory is a consequence of the statistical nature of physical variables.
The chief object of my paper is to clarify the notion of relativity to the means of observation as the basis for description of physical phenomena. This concept is so important that it deserves the name "the principle of relativity to the means of observation." This principle is particularly important to a correct understanding of quantum mechanics. The notion of relativity to the means of observation is, in a certain sense, a generalization of the notion of relativity to the system of reckoning. The two notions play analogous roles in the corresponding theories. But while relativity theory, which rests upon the notion of relativity to the system of reckoning, takes into consideration only the motion of the means of observation as a whole, in quantum mechanics it is also necessary to take note of deeper properties of the means of observation.
The Statistical Interpretation of quantum theory is formulated for the purpose of providing a sound interpretation using a minimum of assumptions. Several arguments are advanced in favor of considering the quantum state description to apply only to an ensemble of similarily prepared systems, rather than supposing, as is often done, that it exhaustively represents an individual physical system. Most of the problems associated with the quantum theory of measurement are artifacts of the attempt to maintain the latter interpretation. The introduction of hidden variables to determine the outcome of individual events is fully compatible with the statistical predictions of quantum theory. However, a theorem due to Bell seems to require that any such hidden-variable theory which reproduces all of quantum mechanics exactly (i.e., not merely in some limiting case) must possess a rather pathological character with respect to correlated, but spacially separated, systems.
This standalone preprint presents the basic principles of Relative Duality, a relational approach to foundational physics in which no background, observer, descriptive role, or external law is physically preferred at the fundamental level. The article introduces the core postulate that physical content consists only of relations and quantities invariant under admissible exchanges of descriptive roles. The paper is written as an accessible foundational note, partly in the spirit of early principle-based formulations of relativity. It explains the intended reciprocity between information and transformation, state and law, geometry and interaction, observer and effective law, and symmetry and admissible dynamics. At the formal level, the article summarizes the role-exchange idea through invariants, equivariant rewriting, and a mutual-commutant relation between represented role symmetries and compatible laws. The article also states a conditional observer-relative reading of space, energy, time, and neutrality, and briefly discusses how the standard Born probability form may be interpreted as an information–transformation pairing once a quantum event structure is assumed. These discussions are explicitly conditional and are not presented as derivations of established physical theories. This work does not claim to derive observed particles, the Standard Model, measured constants, general relativity, quantum field theory, or quantum measurement probabilities from first principles. It is intended as a concise statement of the foundational principles and open requirements of the Relative Duality research program.