It is interesting that ideas showing affinities with the veiled reality concept were independently developed by thinkers working in the field of pure philosophy of science, which means that they did not base their conceptions on detailed physical knowledge of any sort. There can, of course, be no question of presenting a balanced account of these subtle and often quite sophisticated theories. Indeed it is only possible to mention briefly two or three examples, concentrating only on one of them. Difficulty 4a is one facet of the so-called Schrodinger cat paradox, and it may be said to constitute the central riddle of quantum measurement theory, nay, even of the whole of quantum mechanics. Difficulty 4b, the "and-or" difficulty, though often overlooked, is also intriguing. The chapter argues against "nonseparability of empirical reality" by using the idea that in the empirical view ontological considerations should be barred.
It is interesting that ideas showing affinities with the veiled reality concept were independently developed by thinkers working in the field of pure philosophy of science, which means that they did not base their conceptions on detailed physical knowledge of any sort. There can, of course, be no question of presenting a balanced account of these subtle and often quite sophisticated theories. Indeed it is only possible to mention briefly two or three examples, concentrating only on one of them. Difficulty 4a is one facet of the so-called Schrodinger cat paradox, and it may be said to constitute the central riddle of quantum measurement theory, nay, even of the whole of quantum mechanics. Difficulty 4b, the "and-or" difficulty, though often overlooked, is also intriguing. The chapter argues against "nonseparability of empirical reality" by using the idea that in the empirical view ontological considerations should be barred.
By questioning the validity of some of our basic concepts, such as space, object, and causality, quantum physics contributes quite decisively to the dramatic changes now taking place in our world picture.This book is addressed not only to physicists at an early stage in their careers (the first or second year graduate student) but also to philosophers, as well as to all the senior physicists interested in the interpretation problem. Beginning with a chapter that could be described as ?philosophy for physicists,? it presents an in-depth analysis of present-day quantum mechanical concepts, an analysis of physicists and philosophers alike. Specifically, it first offers an extensive critical analysis of such topics as the Einstein, Podolsky, Rosen reality criterion, nonseparatability, the quantum measurement riddle, decoherence theory, consistent histories approaches and ontologically interpretable theories. All this then naturally leads to philosophical questions concerning, in particular, intersubjective agreement and the limit of realism. And a thorough examination of this whole material finally leads to the view that distinguishing between empirical reality and a veiled man-independent reality yields an acceptable answer to the perplexing question of how to interpret quantum physics. Veiled Reality offers nonspecialists, including students in physics, philosophy and the history of science, an accessible perspective on basic problems in the foundations of physics.
This chapter tries to pinpoint the epistemological information that a scientist (or an epistemologist) anxious to keep away from "metaphysical" commitments of any sort may nevertheless derive from quantum physics. But, valuable as it is (mainly as a guide for discriminating the genuinely scientific questions from those of a more "mixed" sort) this standpoint is not to be raised to the status of a universal way of thinking that would be the only admissible one. Within the veiled reality conception Einstemian separability, applies to empirical, not to independent, reality; which means that special relativity theory does not concern independent reality. In his mature years Heisenberg developed a conception of the world in which quite a central role is played by the notion of potentia. He associated wave functions to potentia. In a sense, Heisenberg's approach is ontological, but his ontology is of a subtle kind, for along with actuality it leaves room for potentialities.
Both science and philosophy have been characterized as seeking to understand the nature of reality. They are sometimes even pitted against each other, suggesting that the success of science undermines the relevance of philosophy. But attending to the sort of understanding or explanation being sought offers a different picture: contemporary physics as practiced sometimes fails to provide a clear physical account of the world. This lies at the root of the dissatisfaction with standard quantum theory expressed by Einstein, Schrödinger, and John Bell. As an example, close consideration of Schrödinger's famous cat example suggests that physicists often have missed his point. What a philosophical disposition can contribute is not alternative physics, but rather the sort of careful attention to argument needed to extract a physical picture from a mathematical formalism.
Kantian philosophy provided a strong foundation for classical Newtonian mechanics; however, it is difficult to fully account for the features of quantum mechanics. Functionalized and structured a priori knowledge provides only an additional explanation in terms of the hierarchy and role of knowledge; nevertheless, it does not fundamentally alter Kant’s traditional concept, and the transformed a priori knowledge still fails to reveal the state of knowledge in quantum mechanics. Therefore, this chapter is going to construct a new notion of “trans-empirical” that absorbs both the meanings of transcendental and a priori and the meaning of experience to understand quantum mechanics, so that trans-empirical is itself capable of being linked to experience. The trans-empirical refers to something that surpasses experience but also connects it and enables it. This inherent tension between surpassing and connecting experience is what allows objects in quantum mechanics and superstring theory to possess a trans-empirical feature. Different quantum states correspond to distinct quantum realities, and quantum reality is trans-empirical reality, that is, between the possible world and the real world. A single measurement of a quantum system provides only a partial glimpse of its overall reality. It is the whole of the various realities that completely describes the quantum reality. The basic framework of the trans-empirical reality is: Different trans-empirical concepts + perceptual material, perceptual models → different scientific models (rational models) → different scientific realities (trans-empirical realities). In addition, this chapter presents the model of trans-empirical cognition: Pre-experience → pre-understanding → trans-empirical ideas → perceptual knowledge → trans-empirical concepts → rational knowledge → post-experience.
We have seen, in Section 2.5, how the superposition principle leads to the existence of entangled states of two or more quantum systems. Such states are characterized by the existence of correlations between the systems, the form of which cannot be satisfactorily accounted for by any classical theory. These have played a central role in the development of quantum theory since early in its development, starting with the famous paradox or dilemma of Einstein, Podolsky, and Rosen (EPR). No less disturbing than the EPR dilemma is the problem of Schrödinger’s cat, an example of the apparent absurdity of following entanglement into the macroscopic world. It was Schrödinger who gave us the name entanglement; he emphasized its fundamental significance when he wrote, ‘I would call this not one but the characteristic trait of quantum mechanics, the one that enforces the entire departure from classical thought’. The EPR dilemma represents a profound challenge to classical reasoning in that it seems to present a conflict between the ideas of the reality of physical properties and the locality imposed by the finite velocity of light. This challenge and the developments that followed have served to refine the concept of entanglement and will be described in the first section of this chapter. We start by recalling that a state of two quantum systems is entangled if its density operator cannot be written as a product of density operators for the two systems, or as a probability-weighted sum of such products. For pure states, the condition for entanglement can be stated more simply: a pure state of two quantum systems is not entangled only if the state vector can be written as a product of state vectors for the two systems. In the discipline of quantum information, entanglement is viewed as a resource to be exploited. We shall find, both here and in the subsequent chapters, that our subject owes much of its distinctive flavour to the utilization of entanglement.
The odd concepts of quantum physics are nearly a century old. They may seem difficult and forbidding at first sight, but the barrier to understanding is not their difficulty but their differentness . Unlike classical models, quantum theory does not attempt to simulate Nature. It gives us information about observations of Nature. But it does contain a “theoretical entity” that claims to contain all information, observation notwithstanding, namely the quantum state vector in Hilbert space. Scientists routinely use the language of Hilbert space, and nonscientists do not use it at all, which is understandable but unfortunate. A sort of baby-talk has become the lingua franca for much of the popular journalism of quantum physics, an awkward patois that combines some of the early groping language of Bohr, de Broglie, Schrödinger, and Heisenberg with more modern words about symmetries and states. Earnest amateurs still ask me about the mystery of Bohr orbits. There is no mystery because there are no orbits, except as historical curiosities. Same for “wave–particle duality.” Same for “quantum jumps.” A friend once asked me to address a philosophy seminar about the “paradoxes of quantum mechanics.” He said he had approached C. N. Yang first, who replied “What paradoxes?” There are some mathematical and logical rough spots in our current best theory of matter, and perhaps some of them can be framed as paradoxes. But the theory is actually rather straightforward, and it has a perfectly clear interpretation linked to experiments that, in their simplest form, anyone can perform (and students do routinely in college laboratories). No empirical observations are known that are inconsistent with the quantum framework.