What is quantum mechanics actually telling us about the way that nature works, the way nature "really is" deep down at the bottom? In Nick Herbert's book "Quantum Reality" he discusses eight schools of thought; would anyone would care to comment on the reasonableness of any of these ideas? Are there any new variants of these ideas that have appeared in the last 20 years that physicists take seriously? Are there any new ideas, i.e. interpretations of QM that don't fit into any of these eight ideological boxes? As far as I know, at the time his book came out Cramer's transactional interpretation of QM had not been developed, so am I correct in viewing this as a totally new physical interpretation of QM? Are there any experiments which (at least in principle) could show us which interpretations are right or wrong? ---- Nick Herbert talks about "Quantum Reality": Quantum Reality #1 The Copenhagen Interpretation, Part I - There is no deep reality.... Everyday phenomena are themselves built not out of phenomena but out of an utterly different kind of being. Far from being a crank or minority position, "There is no deep reality" represents the prevailing doctrine of establishment physics.... Quantum Reality #2. The Copenhagen interpretation, Part II - Reality is created by observation....The Copenhagen interpretation properly consists of two distinct parts: I. There is no reality in the absence of observation; 2. Observation creates reality ....John Wheeler's memorable maxim for separating what is real in the world from what is not: "No elementary phenomenon is a real phenomenon until it is an observed phenomenon," Quantum Reality #3 - Reality is an undivided wholeness. The views of Walter Heider exemplify a third unusual claim of quantum physicists: that in spite of its obvious partitions and boundaries, the world in actuality is a seamless and inseparable whole....Heitler accepts an observer-created reality but adds that the act of observation also dissolves the boundary between observer and observed: "The observer appears, as a necessary part of the whole structure, and in his full capacity as a conscious being. The separation of the world into an 'objective outside reality' and 'us,' the self-conscious onlookers, can no longer be maintained. Object and subject have become inseparable from each other." Quantum Reality #4 The many-worlds interpretation. Reality consists of a steadily increasing number of parallel universes.... For any situation in which several different outcomes are possible some physicists believe that all outcomes actually occur. In order to accommodate different outcomes without contradiction , entire new universes spring into being, identical in every detail except for the single outcome that gave them birth. ...Invented in 1957 by Hugh Everett, a Princeton graduate student, the many-worlds interpretation is a latecomer to the New Physics scene. Despite its bizarre conclusion, that innumerable parallel universes each as real as our own actually exist, Everett's many-worlds picture has gained Considerable support among quantum theorists... Quantum Reality #5: Quantum logic (The World obeys a non-human kind of reasoning.) ...we must scrap our very mode of reasoning, in favor of a new quantum logic. ...a few creative logicians amused themselves by constructing "crazy logics" using rules other than Boole's, These deviant designs for AND/OR/NOT, although mathematically consistent, were considered mere curiosities since they seemed to fit no human pattern of discourse. However, according to some New Physicists, one of these crazy logics may be just what we need to make sense out of quantum events. Listen to quantum theorist David Finkelstein calling for mutiny against the rules of Boole: "Einstein threw out the classical concept of time; Bohr throws out the classical concept of truth . . . Our classical ideas of logic are simply wrong in a basic practical way. The next step is to learn to think in the right way, to learn to think quantum-logically." Quantum Reality #6. Neorealism (The world is made of ordinary objects.) An ordinary object is an entity which possesses attributes of its own whether observed or not... The clarity and ubiquity of ordinary reality has seduced a few physicists - I call them neorealists - into imagining that this familiar kind of reality can be extended into the atomic realm and beyond. Quantum Reality #7 Consciousness creates reality... a small faction asserts that only an apparatus endowed with consciousness (even as you and I) is privileged to create reality. The one observer that counts is a conscious observer. ...Eugene Wigner...comments on this ironic turn of events: "It is not possible to formulate the laws of quantum mechanics in a fully consistent way with out reference to the consciousness . . . It will remain remarkable in whatever way our future concepts may develop, that the very study of the external world led to the conclusion that the content of the consciousness is an ultimate reality." Quantum Reality #8. The duplex world of Werner Heisenberg (The world is twofold, consisting of potentials and actualities.) Most physicists believe in the Copenhagen interpretation, which states that there is no deep reality- QR # 1) and observation creates reality QR # 2). What these two realities have in common is the assertion that only phenomena are real; the world beneath phenomena is not. One question which this position immediately brings to mind is this: "if observation creates reality, what does it create this reality out of? Are phenomena created out of sheet nothingness or out of some more substantial stuff?" Since the nature of unmeasured reality is unobservable by definition, many physicists dismiss such questions as meaningless on pragmatic grounds. According to Heisenberg, there is no deep reality - nothing down there that's real in the same sense as the phenomenal facts are real.... "But the atoms and the elementary particles themselves are not as real; they form a world of potentialities or possibilities rather than one of things or facts . . . ...Heisenberg's two worlds are bridged by a special interaction which physicists call a "measurement." During the magic measurement act, one quantum possibility is singled out, abandons its shadowy sisters, and surfaces in our ordinary world as an actual event. Everything that happens in our World arises out of possibilities prepared for in that other-the world of quantum potentia. In turn, our world sets limits on how far crowds of Potentia can roam. Because certain facts are actual, not everything is possible in the quantum world. There is no deep reality, no deep reality-as-we-know-it.... [...cutting towards the end of Nick Herbert's article...] Since these quantum realities differ SO radically, one might expect them to have radically different experimental consequences. An astonishing feature of these eight quantum realities, however, is that they are experimentally indistinguishable. For all presently conceivable experiments, each of these realities predicts exactly the same observable phenomena.