ConclusionsIn the Preface to this book, we started with Alice and Bob having very different views of their observations.Alice used an optical telescope and reported nothing unusual about a distant galaxy that she could see.Bob, on the other hand, detected intense radio activity in that galaxy.Our question was: who has the true view of that galaxy?We advised the reader that the answer is not Alice.Neither is it Bob.The answer is not both of them, nor is it neither of them.It is not a trick question either.So what is the answer that this book would supply?Our answer will come presently.While this book has set forth a definite mathematical perspective on empirical physics, it has contained quite a lot of commentary that might be disparaged as metaphysics or philosophy.Such commentary is generally frowned on in science, because it has no empirical content.It is vacuous.In our defense, we point out the obvious: science is not a robotic activity; it is carried out by humans and these are driven by their metaphysical, philosophical, and emotional imperatives.For instance, the hard-core scientific view that quantum theory needs no interpretation but only application is itself a philosophy.It is no more than a conditioned response, based on opinion and subscription to current scientific norms.It is, indeed, a philosophy of how to do quantum mechanics.So we all do it, in one way or another.Our concern in this book is that the way that we do it should be based soundly on scientific principles.The quantized detector approach that we describe and use in this book is our attempt to do just that.There is an excellent paper on all of this that has the provocative title "Quantum Theory Needs No Interpretation," by Fuchs and Peres (2000).It seems on the face of it to dismiss any sort of "interpretation" of quantum mechanics.In fact, close reading of it confirms (to us at least) the agenda that we have set out in this book.Yes, quantum mechanics needs no interpretation, when it is being applied to processes that take place in the information void.
ConclusionsIn the Preface to this book, we started with Alice and Bob having very different views of their observations.Alice used an optical telescope and reported nothing unusual about a distant galaxy that she could see.Bob, on the other hand, detected intense radio activity in that galaxy.Our question was: who has the true view of that galaxy?We advised the reader that the answer is not Alice.Neither is it Bob.The answer is not both of them, nor is it neither of them.It is not a trick question either.So what is the answer that this book would supply?Our answer will come presently.While this book has set forth a definite mathematical perspective on empirical physics, it has contained quite a lot of commentary that might be disparaged as metaphysics or philosophy.Such commentary is generally frowned on in science, because it has no empirical content.It is vacuous.In our defense, we point out the obvious: science is not a robotic activity; it is carried out by humans and these are driven by their metaphysical, philosophical, and emotional imperatives.For instance, the hard-core scientific view that quantum theory needs no interpretation but only application is itself a philosophy.It is no more than a conditioned response, based on opinion and subscription to current scientific norms.It is, indeed, a philosophy of how to do quantum mechanics.So we all do it, in one way or another.Our concern in this book is that the way that we do it should be based soundly on scientific principles.The quantized detector approach that we describe and use in this book is our attempt to do just that.There is an excellent paper on all of this that has the provocative title "Quantum Theory Needs No Interpretation," by Fuchs and Peres (2000).It seems on the face of it to dismiss any sort of "interpretation" of quantum mechanics.In fact, close reading of it confirms (to us at least) the agenda that we have set out in this book.Yes, quantum mechanics needs no interpretation, when it is being applied to processes that take place in the information void.
In the Preface to this book, we started with Alice and Bob having very different views of their observations. Alice used an optical telescope and reported nothing unusual about a distant galaxy that she could see. Bob, on the other hand, detected intense radio activity in that galaxy. Our question was: who has the true view of that galaxy? We advised the reader that the answer is not Alice . Neither is it Bob . The answer is not both of them , nor is it neither of them . It is not a trick question either. So what is the answer that this book would supply? Our answer will come presently. While this book has set forth a definite mathematical perspective on empirical physics, it has contained quite a lot of commentary that might be disparaged as metaphysics or philosophy. Such commentary is generally frowned on in science, because it has no empirical content. It is vacuous. In our defense, we point out the obvious: science is not a robotic activity; it is carried out by humans and these are driven by their metaphysical, philosophical, and emotional imperatives. For instance, the hard-core scientific view that quantum theory needs no interpretation but only application is itself a philosophy. It is no more than a conditioned response, based on opinion and subscription to current scientific norms. It is, indeed, a philosophy of how to do quantum mechanics. So we all do it, in one way or another. Our concern in this book is that the way that we do it should be based soundly on scientific principles. The quantized detector approach that we describe and use in this book is our attempt to do just that. There is an excellent paper on all of this that has the provocative title “Quantum Theory Needs No Interpretation,” by Fuchs and Peres (2000). It seems on the face of it to dismiss any sort of “interpretation” of quantum mechanics. In fact, close reading of it confirms (to us at least) the agenda that we have set out in this book. Yes, quantum mechanics needs no interpretation, when it is being applied to processes that take place in the information void .
Abstract The strange behaviour of photons described in the last chapter immediately raises all sorts of difficult questions about the meaning of quantum theory. We might be encouraged to look for this meaning by going back to the theory’s mathematical formalism, perhaps by trying to find out how we might better interpret some of its elements. However, it is a central argument of this book that, no matter where we look, we are always led back to philosophy. At first sight, this might seem to be an odd thing to claim. After all, modem textbooks on quantum physics and chemistry rarely (if ever) discuss philosophy. We accept that the behaviour of photons is strange, but surely it is something that we can at least study experimentally—do we need philosophy in these circumstances? The answer is most certainly yes. Quantum theory directly challenges our understanding of the nature of matter and radiation, and the process of measurement at their most elementary levels, and we cannot go forward unless we adopt some kind of interpretation, some way of trying to make sense of it all. As we will see, this interpretation has to be based on some philosophical position.
There are several (general) philosophy of physics textbooks on the market.1 An
obvious question to ask at the outset then is: Why another one? In his “Some
Philosophical Aspects of Particle Physics”, Michael Redhead bemoans the common practice of philosophers of science of dealing with examples “which are no
longer of current research interest in science” ((1980), p. 279). This practice is
still common even among many philosophers of physics, and, for the most part,
the available textbooks continue to engage in this practice. Generally, one finds a
little spacetime, a little statistical mechanics, and a little quantum theory. Now,
these are of course the ‘pillars’ of modern physics, so it is what we should expect
to be covered in any textbook on the philosophy of physics worth its salt (and,
indeed, they are well represented in this book). However, the issues that are
dealt with are usually very old fashioned and very limited in scope: ‘spacetime’
means ‘the twins paradox’ (and possibly conventionalism); ‘statistical mechanics’
means ‘time asymmetry’; and ‘quantum theory’ means ‘the measurement problem’. Redhead is surely right that this leads physicists to “regard philosophy of
science as somewhat irrelevant”. Rightly so, too, if this were in fact representative of much of what actually goes on in philosophy of physics. However, the
state of play as represented in philosophy of physics and (some) philosophy of
science journals shows a very different level of engagement, with philosophers
of physics investigating the frontiers of scientific research. This disparity (or the
impression of such) is the raison d’eˆtre for the book you are now reading. The result is an introductory textbook covering those portions of philosophy of physics
research that other textbooks fail to cover, or cover only very briefly or very
simplistically. The three pillars of modern physics-relativity, quantum theory
and statistical mechanics-are still represented, then, but from a more advanced
and contemporary perspective.
Abstract Metaphysicians should pay attention to quantum mechanics, but not because it provides definitive answers to many metaphysical questions. The theory itself is remarkably silent on the nature of the physical world, and the various interpretations of the theory on offer present conflicting ontological pictures. Rather, quantum mechanics is essential to the metaphysician because it reshapes standard metaphysical debates and opens up unforeseen new metaphysical possibilities. Even if quantum mechanics provides few clear answers, there are good reasons to think that any adequate understanding of the quantum world will result in a radical reshaping of our classical worldview in some way or other. Whatever the world is like at the atomic scale, it is almost certainly not the swarm of particles pushed around by forces that is often presupposed. This book guides readers through the theory of quantum mechanics and its implications for metaphysics in a clear and accessible way. The theory and its various interpretations are presented with a minimum of technicality. The consequences of these interpretations for metaphysical debates concerning realism, indeterminacy, causation, determinism, holism, and individuality (among other topics) are explored in detail, stressing the novel form that the debates take given the empirical facts in the quantum domain. While quantum mechanics may not deliver unconditional pronouncements on these issues, the range of possibilities consistent with our knowledge of the empirical world is relatively small—and each possibility is metaphysically revisionary in some way.
Quantum mechanics is usually defined in terms of some loosely connected axioms and rules. Such a foundation is far from the beauty of, e.g., the `principles' underlying classical mechanics. Motivated, in addition, by notorious interpretation problems, there have been numerous attempts to modify or `complete' quantum mechanics. A first attempt was based on so-called hidden variables; its proponents essentially tried to expel the non-classical nature of quantum mechanics. More recent proposals intend to complete quantum mechanics not within mechanics proper but on a `higher (synthetic) level'; by means of a combination with gravitation theory (R Penrose), with quantum information theory (C M Caves, C A Fuchs) or with psychology and brain science (H P Stapp). I think it is fair to say that in each case the combination is with a subject that, per se , suffers from a very limited understanding that is even more severe than that of quantum mechanics. This was acceptable, though, if it could convincingly be argued that scientific progress desperately needs to join forces. Quantum mechanics of a closed system was a beautiful and well understood theory with its respective state being presented as a point on a deterministic trajectory in Liouville space---not unlike the motion of a classical N -particle system in its 6N -dimensional phase-space. Unfortunately, we need an inside and an outside view, we need an external reference frame, we need an observer. This unavoidable partition is the origin of most of the troubles we have with quantum mechanics. A pragmatic solution is introduced in the form of so-called measurement postulates: one of the various incompatible properties of the system under consideration is supposed to be realized (i.e. to become a fact, to be defined without fundamental dispersion) based on `instantaneous' projections within some externally selected measurement basis. As a result, the theory becomes essentially statistical rather than deterministic; furthermore there is an asymmetry between the observed and the observing. This is the point where consciousness may come in. Complemented by an introduction and several appendices, Henry Stapp's book consists essentially of three parts: theory, implications, and new developments. The theory part gives a very readable account of the Copenhagen interpretation, some aspects of a psychophysical theory, and, eventually, hints towards a quantum foundation of the brain--mind connection. The next part, `implications', summarizes some previous attempts to bridge the gap between the working rules of quantum mechanics and their possible consequences for our understanding of this world (Pauli, Everett, Bohm, Heisenberg). The last section, `new developments', dwells on some ideas about the conscious brain and its possible foundation on quantum mechanics. The book is an interesting and, in part, fascinating contribution to a field that continues to be a companion to `practical' quantum mechanics since its very beginning. It is doubtful whether such types of `quantum ontologies' will ever become (empirically) testable; right now one can hardly expect more than to be offered some consistent `grand picture', which the reader may find more or less acceptable or even rewarding. Many practicing quantum physicists, though, will remain unimpressed. The shift from synthetic ontology to analytic ontology is the foundation of the present work. This means that fundamental wholes are being partitioned into their ontologically subordinate components by means of `events'. The actual event, in turn, is an abrupt change in the Heisenberg state describing the quantum universe. The new state then defines the tendencies associated with the next actual event. To avoid infinite regression in terms of going from one state of tendencies to the next, consciousness is there to give these events a special `feel', to provide a status of `intrinsic actuality'. The brain of an alert human observer is similar in an important way to a quantum detection device: it can amplify small signals to large macroscopic effects. On the other hand, actual events are not postulated to occur exclusively in brains. They are more generally associated with the formation of records. Records are necessarily part of the total state of the universe: it is obvious that the state of the universe cannot undergo a Schrödinger dynamics and at the same time record its own history. `The full universe consists therefore of an exceedingly thin veneer of relatively sluggish, directly observable properties resting on a vast ocean or rapidly fluctuating unobservable ones.' The present ideas also bear on how the world should be seen to develop. While conventional cosmology encounters problems as to how to define the intial conditions, which would enter the governing equations of motion, here `the boundary conditions are set not at some initial time, but gradually by a sequence of acts that imposes a sequence of constraints. After any sequence of acts there remains a collection of possible worlds, some of which will be eliminated by the next act.' Connected with those acts is `meaning': there has always been some speculation about the special significance of local properties in our understanding of the world. One could argue that correlations (even the quantum correlations found, e.g., in the EPR-experiments) were as real as anything else. But also Stapp stresses the special role of locality: the `local observable properties, or properties similar to them are the natural, and perhaps exclusive, carriers of meaning in the quantum universe. From this point of view the quantum universe tends to create meaning.' This sounds like an absolute concept: meaning not with respect to something else, but defined intrinsically---not easy to digest. The role of consciousness in the developing quantum universe requires more attention. `The causal irrelevance of our thoughts within classical physics constitutes a serious deficiency of that theory, construed as a description of reality.' This is taken to be entirely different within quantum mechanics. `The core idea of quantum mechanics is to describe our activities as knowledge-seeking and knowledge-using agents.' `21st century science does not reduce human beings to mechanical automata. Rather it elevates human beings to agents whose free choices can, according to the known laws, actually influence their behaviour.' An example with respect to perception is discussed: `Why, when we look at a triangle, do we experience three lines joined at three points and not some pattern of neuron firings?' The brain `does not convert an actual whole triangle into some jumbled set of particle motions; rather it converts a concatenation of separate external events into the actualization of some single integrated pattern of neural activity that is congruent to the perceived whole triangle.' How convincing is this proposal? It is hard to tell. I think Henry Stapp did a good job, but there are tight limitations to any such endeavour. Quantum mechanics is often strange indeed, but it also gives rise to our classical world around us. For the emergence of classicality jumps and measurement projections (the basic phenomena connected with those fundamental events of choice) are not needed. Therefore, I doubt whether the explanation of the evolution of our world really allows (or requires) that much free choice. On the other hand, most scientist will agree that empirical science was not possible without free will: we could not ask independent questions if this asking was part of a deterministic trajectory. The fact that the result of a quantum measurement is indeterminate (within given probabilities) does certainly not explain free will. How about the type of measurment? The experimentalist will have to assume that he can select the pertinent observable within some limits. But given a certain design the so-called pointer basis (producing stable measurement results) is no longer a matter of free choice. `The main theme of classical physics is that we live in a clocklike universe.' Today it is often assumed that the universe was a big (quantum-) computer or a cellular automaton. Many would be all too happy to leave that rather restrictive picture behind. But where to go? Stapp suggests giving consciousness a prominent role: `The most profound alteration of the fundamental principles was to bring consciousness of human beings into the basic structure of the physical theory.' How far we are able to go in this direction will depend on the amount of concrete research results becoming available to support this view.
This book had as its main objective to discuss how (quantum) physics concepts could be used in a relevant way in the modeling of a variety of economics/finance and psychology-based processes. For those readers who have come to read this conclusion, without skipping its “backbone,” we would like to say “thank you” for keeping with us until the end. The possible claim, which says that social science driven dynamics would need analyzing with techniques from the natural sciences, may well have been tempered with this book. Although quantum physics as a theory of prediction is one of the most successful theories humankind ever devised, it is not unreasonable to suggest that the number of foundational interpretations of quantum physics is sizable. Consider now the following natural question: “How can a theory with such a wide diversity of foundational interpretations serve to inform and elucidate a non-cognate area of research (like economics or psychology)?” Indeed, we should want to stand upright and write, without hesitation, the words “non-cognate.” No theory in social science can come close to the predictive power of quantum physics. However, very few social science theories are “plagued” by foundational issues of such depth as quantum physics. As an example, consider the issue of why quantum physical wave functions do have to be complex valued. Do physicists have a satisfactory answer to this very basic question? A theory of such predictive power has a partial differential equation, the Schrödinger equation, which cannot be rigorously derived. However, in economics and finance we strive to build theoretical edifices with the utmost respect for rigor.