Complementarity, Bell’s Theorem, and the Framework of Process Metaphysics

by Henry J. Folse, Jr.

Henry J. Folse, Jr. is Associate Professor of Philosophy at Loyola University, New Orleans, Louisiana.

The following article appeared in Process Studies, pp.259-273, Vol. 11, Number 4, Winter, 1981. Process Studies is published quarterly by the Center for Process Studies, 1325 N. College Ave., Claremont, CA 91711. Used by permission. This material was prepared for Religion Online by Ted and Winnie Brock.


Realism and quantum mechanics can both be retained once the ontology of classical materialism is fully relinquished. Process metaphysics has injected into the career of philosophy crucial ontological conceptions, both critical and constructive, which may well serve as seeds from which a fuller understanding of the nature of the physical world, in both science and philosophy, may grow.

Throughout the last fifty years various philosophers and physicists have attempted to assess the extent of agreement between the conception of physical reality within the framework of process philosophy and the character of the physical world described by quantum theory.1 Recently this line of inquiry has been given new life by the discovery of Bell’s theorem. This theorem and its experimental disconfirmation appear to imply that we must radically revise our ideas about the spatiotemporal description of the elementary physical entities represented by the equations of quantum mechanics.2 Since this is an issue on which Whitehead focused a great deal of his criticism of classical physics, it is not surprising that Bell’s theorem has occasioned considerable interest among process philosophers.3

Although it is perhaps not widely recognized, a similar concern with a critique of the classical concepts used in the spatiotemporal description of physical reality is the cornerstone on which Niels Bohr erected his framework of "complementarity" designed to resolve the paradoxes of quantum theory. Juan earlier paper I considered some of the common features of Bohr’s interpretation of quantum theory and Whitehead’s process philosophy (1:32-47). Here I propose to revise that analysis somewhat by presenting an overview of the conceptual path which led Bohr to complementarity and showing it to be analogous to the twin tools which Whitehead used to clear a conceptual space in which to build his process framework.4 In particular I intend to show how the experimental tests of Bell’s theorem confirm the outlook of both Bohr and Whitehead, thus strengthening the potential alliance between these two frameworks.

1. Conceptual Frameworks and the Philosophy of Science

Quite independently of recent developments in quantum physics, philosophy of science recently has undergone a prodigious upheaval which has ended the regime of the so-called "orthodox" or "received view" -- inspired by positivism -- that once utterly dominated the field. Whatever might be the final outcome of this revolution -- and this issue still seems very much unresolved -- it now appears quite clear that the erstwhile antimetaphysical bias of philosophy of science is being replaced by a new sensitivity to the role of the conceptual framework within which any scientific description of reality is offered for acceptance.

What I am calling "conceptual frameworks" might be called by different names and of course vary considerably from one philosopher to the next. However, what most challenges to the received view seem to share in common is the recognition that what makes possible the advance of the scientific understanding of nature is not captured by a model that bases scientific theories on a foundation of allegedly certain, unproblematic, directly known observation statements. Instead, it appears that science devises continuous modifications of its descriptive concepts and their interrelations in ways which lead to an ever-widening base of possible observations as interpreted within the conceptual scheme.5 This process embodies a rationality or rationalities which may take into account a host of factors other than experimental observations. A conceptual framework provides the concepts in terms of which theoretical representations are understood as describing reality. But in doing so, it also essentially embodies fundamental ontological presuppositions about physical reality and stipulates ideal standards of what is to count as an acceptable description of phenomena given within the framework.6

My point in mentioning this changed outlook is to draw attention to the fact that philosophy of science appears to be moving towards the conclusion that progress in understanding nature involves an ongoing critique of the conceptual framework within which science describes the physical world. The time once was that philosophers had an important role in precipitating such a critique -- or perhaps more accurately: those who performed it were both scientists and philosophers. However, partly due to the increasingly technical nature of science and partly due to the positivistic antimetaphysical attitude which has prevailed in philosophy of science, in this century such a critique has been left almost exclusively in the hands of scientific specialists. The most notable exception is Alfred North Whitehead.

As a philosopher who was very much sensitive to how the conceptual scheme of science had to be changed, Whitehead was able to put his finger on two of the weakest points in the classical framework. Indeed, as the pressure for change coming from quantum theory has intensified in the years since Whitehead wrote, these two points have exhibited an ever greater degree of conceptual tension. The first is the assumption that the reality described by classical physics consists of entities having the properties of existing at a determinate location in space at each instant in time. Since such entities are regarded as "substances" and thus can be known only through their properties, as far as the framework of classical physics is concerned, these entities are defined by a spatiotemporal mode of description. What a thing is, is, in essence, where that thing is in space and time. Where a thing is not, it can have no property and so no causal effect. This line of reasoning led to a view of the universe in which the interrelatedness of things was ultimately a mystery. Whitehead called it the fallacy of simple location.

In 1964 J. S. Bell showed that if we assume, in accord with the classical framework, that quantum mechanical descriptions are descriptions of the properties of simply located elementary particles, than the mathematics of quantum theory allows us to derive an inequality -- now known as "Bell’s theorem" -- which essentially places a limit on the number of pairs of particles with certain specified properties one should be able to detect experimentally. However, the evidence now strongly confirms that in actual observation this limit is exceeded. Thus if we assume that the quantum formalism is correct, as seems to be dictated by overwhelming experimental corroboration, then the assumption that quantum mechanics describes simply located particles must be regarded as false. Thus today it would seem that this experimental disconfirmation of Bell’s theorem has confirmed Whitehead’s attempt to restructure our thinking with respect to the doctrine of local causes.

Whitehead’s second criticism concerned the tendency of classical physics to regard its theoretical representation of an object interacting with human sense organs to cause experience as a description of the real entities of the world. The experiences which confirm such theoretical representations are understood as the causal effects of these allegedly real objects which populate the physical universe. Whitehead called this line of argument the fallacy of misplaced concreteness. As in the case of the fallacy of simple location, the failure to confirm Bell’s theorem would not have surprised Whitehead, for deriving that theorem assumes that the mathematical abstraction of a simply located particle is a direct representation of the real object of a quantum mechanical description. In other words, Bell’s derivation depends on committing the fallacy of misplaced concreteness.

Of course Whitehead launched his critique primarily in response to relativity. The quantum theory which influenced him was the "old quantum theory" of Planck and Bohr’s atomic model, not the new quantum theory of 1925-27 proposed by Heisenberg and Schrödinger. It is this latter theory which uncompromisingly defies the classical mode of description and brings forward the demand -- crystallized in the indeterminacy relations of Heisenberg -- for a renewed critique of the classical descriptive concepts.

The person who first met this demand directly was the patron spirit of the whole quantum revolution and the mentor of Heisenberg: Neils Bohr. Unfortunately, because Bohr was a physicist, not a philosopher, his attempt to formulate a new framework which would rationally generalize the framework of classical physics focused quite naturally on specific quantum problems and assiduously skirted overtly metaphysical issues. Nevertheless, Bohr made it quite clear that he was not merely providing an interpretation of quantum mechanics, although that was of course his professional objective and virtually the only aspect of his work considered today. Instead, he was attempting to provide a new "viewpoint" which would replace the classical world-view. And, like Whitehead, he also made it quite clear that this new framework was to be developed by analyzing the classical descriptive concepts and their incompatibility with quantum demands. He called this new framework "complementarity."

2. The Framework of Complementarity

Bohr’s failure to present complementarity in a systematic way as a framework for describing all of nature has hindered appreciating the significance of his revision of the conceptual scheme of classical physics. Since complementarity is generally read as a way of "explaining" either the indeterminacy relations or wave-particle dualism, it is not widely understood that Bohr arrived at his position essentially through an analysis of classical physics. Furthermore, Bohr’s reluctance to comment on the metaphysical implications of his framework and the fact that it was proposed during the heyday of positivism have conspired to produce an amazing number of misunderstandings concerning complementarity.

Most commonly it is believed that Bohr argued against realism in behalf of the instrumentalist interpretation of scientific theory, holding that wave and particle representation of quantum systems were merely theoretical devices useful for predicting the outcome of particular measurement operations in different experimental situations. Sometimes we find it leads to correct predictions to use the particle "inference ticket" and sometimes the wave. But since scientific theory -- on the instrumentalist account -- does not intend to describe how the world really is, there is no inconsistency in using representations which, if interpreted realistically, would attribute incompatible properties to the entities described by quantum theory. Particles and waves are thus "complementary" conceptual tools for getting at correct predictions of phenomenal observations.

This facile distortion of Bohr’s intention can easily be dispelled by the careful reading of his early papers on the subject (ATDN). Indeed, Bohr argues that the complementarity of particle and wave "pictures" is a consequence of the fact that observation must be theoretically represented as an interaction in which one of the interacting physical systems is understood to be the real object which quantum theory attempts to describe. When Bohr unveiled his philosophical discovery, the term "complementarity" was first used to characterize a relationship between two "modes of description":

The very nature of the quantum theory thus forces us to regard the space-time co-ordination and the claim of causality, the union of which characterizes the classical theories, as complementary but exclusive features of the description, symbolizing the idealization of observation and definition respectively. (ATDN 54f.)

In order to understand what these two modes of description entail and why they can no longer be applied as they were in the classical framework, it is necessary to retrace briefly Bohr’s conceptual critique of the classical framework.

Bohr’s revolution starts with his acceptance of the "quantum postulate." This postulate states that as an empirical fact it is necessary to describe atomic systems as existing only in certain discrete or "stationary" states defined by reference to Planck’s quantum of action. In changing from one state to another, quantum systems "jump" discontinuously from one discrete state to another. Since mechanical states are defined in terms of the parameters of space, time, momentum, and energy, and since on the classical view these parameters are defined as continuous, in that framework, in general, change of state is represented as taking place continuously. But in the framework intended to resolve the quantum paradoxes, elementary entities must be understood as changing their state discontinuously. As Bohr understood his task, a "rational generalization" of the classical framework must make possible harmonizing the quantum postulate with those aspects of the classical framework that must be retained to allow an unambiguous description of the experimental results necessary to secure the objectivity of that description.

Let us consider how the classical framework made the descriptive goals of classical mechanics attainable. If we focus on describing an isolated body moving through space, we can regard the task of mechanics as successfully completed if we can develop a formalism which, given certain initial conditions, will allow us to determine the spatial locus of the body at each instant in time. Bohr calls a description of this sort a description which employs the mode of "space-time co-ordination." Insofar as Bohr’s framework of complementarity seeks to alter our understanding of the mode of description of space-time co-ordination, like Whitehead, Bohr is committed to a critique of the classical doctrine of simple location. The acceptance of a particular mechanics, i.e., a particular set of laws governing such motion (e.g., Newton’s mechanics), is a function of the degree to which the deductive consequences of its formalism accord with observations of the body it is intended to describe. Insofar as these bodies are planets or other large objects which can be observed by direct visual means space-time co-ordination can be attained by observation involving no particular conceptual difficulties ("the idealization of observation" in Bohr’s words). Thus although in a strict sense even just looking at the moon does involve an interaction between the moon and the light which will reach the eye, the way in which such an interaction changes the state of the moon is so minute as to be utterly negligible. Hence, as an idealization so close to reality that this discrepancy could never be detected, looking at the moon may be regarded as an observation which determines the moon’s position as it is in complete isolation from the observer and the light which reaches his/her eye.

However, when we consider objects that cannot be so simply observed visually, we will be forced to determine their position through various instruments: the "measuring" or "observing system." Still, the classical framework is easily able to handle this task for it can invoke the fundamental principles of conservation of momentum and energy. Using this aspect of the classical formalism (in Bohr’s words, "the claim of causality"), we consider the observed object and the observing system as two physical systems in interaction. The measuring apparatus is so constructed that we can determine its mechanical state in a way such that the interaction involved changes its state no more than looking at the moon -- for example, reading a pointer on a meter. If we arrange to have the observed system interact with the measuring and observing systems prior to the observational interaction, and we can unproblematically determine the state of the observing system after the interaction, we can use the conservation principles to determine just how the state of the observed system was changed in the observation in order to define its state (the "idealization of definition") at the instant the interaction is complete. Bohr calls this aspect of the description the mode which employs the "claims of causality" because the interaction is essentially the way in which the state of one system causally affects the state of the other.

However, in order to employ the conservation principles to define the state of the system as isolated once the interaction is completed, we need to assume that the observed system is in some mechanical state throughout the interaction and that this state is changing continuously up to the instant the interaction ceases. Only by making this assumption can we legitimize the conclusion that the state of the observed system at the last instant of the interaction is negligibly different from the state of that system the moment it is isolated from the observing system.

But this is precisely the presupposition which the quantum postulate forces us to discard. Since according to the quantum representation states do not necessarily change continuously throughout an interaction -- indeed it is impossible even to define separate states for the two systems while interacting -- it follows that the two systems cannot be understood as continuously changing their states. As a direct consequence of the quantum formalism we cannot define a state function for the state of the observed system in the course of its interaction with another system; thus the formalism does not permit us to determine a specific classical state for the observed system once it is isolated from the observing interaction. We can, however, consider the interacting systems as a single whole system and formulate a state function representing the two systems together as a single object of description. From this function we can derive a probability for finding the observed system in some particular state after the observation has ceased. This fact gives to the processes of interaction as represented in quantum theory a feature of wholeness or "individuality" as Bohr called it. Any attempt to represent the state of the two systems separately involves an "abstraction" from the concrete physical situation which the quantum formalism is designed to represent. Such an attempt would be precisely what Whitehead called the fallacy of misplaced concreteness; thus like Whitehead Bohr also criticizes this tendency in so interpreting the physical description of nature.

From this line of argument it follows that to observe an isolated physical system is quite literally a contradiction in terms once the quantum postulate is accepted. Within the classical framework, however, the claim that mechanistic physics presented an "objective" description of physical reality was justified by the belief that it determined the properties of substances as they exist quite independently of our observation of them. These properties (spatiotemporal positions) were regarded as the mechanical causes of the observables (spatiotemporal measurements) which empirically confirmed the theory that was expressed in terms of mathematical parameters (spatiotemporal variables in equations) operationally coordinated with the observables. Thus theoretically representing the state of a physical system as isolated from any mechanical interaction was equivalent to determining the properties possessed by a substance as it exists independently of the observation. If we remain within this classical framework, then, since quantum theory cannot so represent the classical state of an isolated system, it follows that either it is an incomplete theory or its description is not objective.

Of course, if we want to defend the claim that quantum theory provides an objective description of its objects, then we must alter the framework to provide a new notion of what such objects are. Bohr’s reasoning followed exactly this path, but though he attempted to formulate a new framework, he avoided stipulating what the ontology of such objects would involve.

First he considered that in order to describe the outcome of a measurement we need to retain an objective means of describing the state of the measuring apparatus. For this task classical mechanics had already provided a totally acceptable method, the method of space-time coordination. This method maybe retained -- indeed Bohr would have said it must be -- because in dealing with the measuring apparatus, we must ultimately deal with physical systems with dimensions such that observing them involves an interaction so small that it can be neglected. This is in fact true by definition; it is what we mean by a "measuring system." Thus the mode of space-time coordination must be retained for describing experimental outcomes.

Secondly, Bohr noted that in order to be able to use the observing interactions as measurements of anything we must consider such observations as involving causal interactions. Only in this way is it possible for the conservation principles to permit determining the state of the observed system by means of its interaction with the observing system. Thus the claims of causality must also be retained. But, because of the quantum postulate, both modes of description cannot be considered as describing the same object. Thus we must conclude that what it is that we are describing using one mode is quite distinct from what it is that we are describing using the other mode. However, the two modes must combine to allow a "complete" description in that the description furnished by one mode is the starting point for the application of the other mode and vice versa. The two modes are thus said to be "complementary." Since Bohr arrives at the complementarity of these modes of description by a critique of the belief that a mathematical representation of a particle at a simple location in space is a description of a real object, and since assuming this belief is necessary for deriving Bell’s theorem, it follows that the disconfirmation of Bell’s theorem amounts to an indirect confirmation of complementarity.

The price to be paid for recognizing that the two modes of description do not apply to the same object of description is that we must relinquish the classical realistic belief that what we are describing in mechanics are the properties possessed by a substance. As mentioned, Bohr assiduously avoided any such overtly metaphysical claim, thereby leaving himself open to being hailed as an ally of the instrumentalists. However, throughout his whole life’s work it is clear that he regarded the task of physics as the description of physical reality, not simply the invention of mathematical schemes allowing correct predictions of experimental results. Whether or not the elementary entities described by quantum physics are particles or waves, it is quite clear that whatever they are Bohr regarded them as real things in the physical world -- as entities which causally interact with our measuring apparatus to produce the experimental observations that confirm the theory. They are not merely inference tickets allowing correct predictions but having no correlation to the way the world "really is."

What is it, then, that the two modes do describe, and what is the relationship of these "objects of description" to the "real entities" which quantum theory symbolizes by its state functions and which interact with the measuring apparatus to produce the phenomena we observe? First consider the observing interaction from a complementaristic viewpoint. In order to use this interaction as an observation not only must we know the state of the observing system before and after the experiment -- recall that its state must be determined unproblematically in the classical fashion -- but also we must know the state of the observed system prior to the observation; at least the theory must provide a function representing that state which can enter into the theoretical description of the interaction that employs the conservation principles. But this means that we must have a theoretical representation of the state of the isolated system, and that is, of course, what observation in the classical scheme was intended to establish by means of the mode of space-time coordination. But now once the quantum postulate is accepted, observation cannot be regarded as determining the state of the isolated physical system. Thus when we theoretically construct a function which represents the state of the system prior to the interaction, i.e., as isolated, the "object" so described must be understood as a conceptual abstraction or idealization, not a "picture" (Bohr’s word) of the entity existing in isolation from the observation as it is in-itself.

Idealization or abstraction though it may be, it is not for that reason one with less importance in quantum physics than it was in the classical framework, for it is the essential requirement for using the other mode of description -- that of describing causally interacting systems through the conservation principles -- in order to describe the measurement interaction as an observation of the state of the observed system. Complementarily, that other mode, the mode employing the claims of causality, is essential to determining the state of the system at some prior time so that we can provide a spatiotemporal description of the isolated system immediately before a particular measurement interaction begins. Thus the two modes mutually support each other, but the object of’ the mode of space-time coordination -- the state of the system as isolated from the interaction -- is itself a theoretical abstraction. Just as Whitehead reminded us in the fallacy of misplaced concreteness, Bohr also insists that we must not mistake it for the actual reality which causes our experiences.

What then is the object which the causal mode describes? It cannot be the real entity as it exists apart from observation either, for the causal mode describes an interaction, and in quantum interactions the state of the observed system cannot be separated from the observing system. Thus the only "object" which is described when the causal mode is invoked to describe an interaction is the whole phenomenon of the interaction itself. We do not in this mode describe two distinct things at all; we describe one thing: an interaction. It would seem, then, that this object of description in the causal mode is no more a substance possessing properties than was the object of the mode of’ space-time coordination. What we are describing in this mode is a change that has an indivisibility or individuality that cannot, on pain of ambiguity, be further subdivided; it is a whole process of change. Again Whitehead’s view seems to accord well with complementarity.

It appears that in neither mode of description does complementarity hold that quantum theory allows a description of a real entity existing apart from observation. Certainly this conclusion is correct if we assume that "describing reality" means, as the classical framework stipulates, determining the properties of a substance, in particular the properties coordinated with the mechanical state parameters. But what if reality is not in fact composed of such entities? Can we formulate an alternative framework in which reality is not so conceived and in which it is understood in a way that does allow us to regard the quantum theoretical representation as in fact describing a real entity? It is at this point that Bell’s theorem provides a helpful clue.

3. The Ontological Significance of Bell’s Theorem

Bell’s theorem is essentially the latest chapter in a story that begins with the confrontation between Bohr and Einstein concerning the completeness of the quantum mechanical description of reality. Although the participants in the debate tended to see the question as whether or not the indeterminacy relations could be violated, in fact the point of issue was not one in physics but in metaphysics. Remaining true to the classical conception of reality, Einstein held that the parameters defining the classical mechanical state are essentially theoretical representations of properties possessed by the entities themselves. Since it is well known the indeterminacy principle prevents determining simultaneously the properties that define the classical mechanical state, if Einstein’s conception of reality is retained, there are properties of real entities which quantum theory cannot determine. Thus the theory is said to be "incomplete." Einstein attempted to make good this argument by designing a series of thought experiments -- the last of which was the celebrated "Einstein-Podolsky-Rosen experiment" -- which would permit determining more than the indeterminacy relations allowed, thus proving the incompleteness of quantum theory. However, his argumentation premised the classical conception of reality; thus for Bohr, who rejected this notion of reality, Einstein’s reasoning quite naturally appeared unsound. The controversy, then, turned on opposing conceptions of physical reality.

Bell’s theorem enters into this story by proposing a possible experimental test of which conception of reality accords with observation. To derive Bell’s theorem one must accept the classical realist’s assumption that the observables recorded in an experiment are the causal effects of properties possessed by the quantum mechanical entity. In order to make the argument go through, one must further assume that if we can demonstrate by observation a correlation between the properties of two systems which once interacted in the past, then the properties in question must have been possessed by the systems when they interacted, even though the observations which determine these properties are made long after the interaction between the systems has ceased. This assumption, in turn, is justified by tacit appeal to the classical belief that the two systems once separated are simply located where they are observed and that therefore no causal relationship between them can exist. A theory which accords with these presuppositions of the classical framework is called a "local realistic theory." With these assumptions Bell derives an inequality concerning the numbers of pairs of particles that will be observed having a particular pair of properties. The quantum formalism predicts that in certain cases this inequality will be violated, and experimental evidence now appears to support its prediction against those of the local realistic theories. This experimental disconfirmation of Bell’s inequality implies that one or more of the classical presuppositions from which it is derived must be false.

It is pointless to repeat a detailed qualitative description of these experiments -- for which the reader is referred to the literature cited above -- but in order to see how complementarity would explain why Bell’s inequality is not confirmed, we need consider only the following facts. In any experimental setup it is impossible in principle to design apparatus which would determine two observables which the indeterminacy principle prohibits determining with arbitrary accuracy. However, we can consider two entities which interact in a way such that the observable detected when entity A is observed hears some strict correlation with the same observable which entity B exhibits when it is observed. Thus from the knowledge of an observable determined from a measurement interaction on entity A, because we know that there is a strict correlation of this observable with that of entity B, we should be able to predict the value of the same observable if entity B is observed.

Indeed such a correlation is found in the case of the spin measured along some coordinate axis of each of a pair of protons which have been allowed to interact in a well-known configuration called the singlet state. At a crucial step in the reasoning, Bell’s derivation then argues that since there is a well-confirmed correlation between the spins of the two protons, it follows that what is observed in the measurement of the spin of proton A is the effect of a property possessed by that proton when it was in interaction with proton B well before the spin was determined by observation. The observation cannot record an effect which arises merely ip the measurement interaction, for that measurement can take place long after the two protons have separated. If the spin of proton A only comes into being when observed, how could that which causes the observation of a particular spin bear a strict correlation with the spin property of proton B since it would not have come into existence until long after the interaction with proton B had ceased? Furthermore, we can observe the two protons with separate spin detectors at the same time even though they are separated by a distance so great that a causal interaction between proton A and proton B at the instant of measurement would have to propagate through space faster than light.

From the viewpoint of complementarity, the negative outcome of experiments testing Bell’s inequality is a victory that could have been expected because the arguments from which the inequality is derived commit the very same fallacies that Whitehead named in his critique of the classical framework. Consider first the description of proton A. We can describe its state after the interaction with proton B has ceased as that of a particle moving through space in a spatial region far from proton B. In the interval between the interaction with proton B (which is allegedly when the relationship to the spin of proton B is determined) and the observation that determines the spin of proton A, we can consider proton A to be an isolated physical system. Indeed, in order to describe the measurement as a measurement of the spin of proton A it is essential that we do so. This state of the isolated proton can be represented as a particle moving through space from the point where the two protons interacted to the point where the spin measurement is made. But, as we have seen, complementarity insists that this representation "describes" an abstraction which is required for our theoretical representation of the measurement interaction but cannot be regarded as a description of the properties of a substantial object existing independently of observation. Consequently when classical realism does in effect argue that the spin of the proton is a property of the proton prior to observation, it assumes that a theoretical representation of what happens in the observing interaction is a description of the real entities that interact to produce the experimental phenomena. In this way classical realism commits the fallacy of misplaced concreteness: it regards the theoretical representation as a description of the properties of an objective reality.

At the same time in arguing that the two protons are entities existing where the spin detectors interact with them, and that they are so separated that a signal cannot pass from one proton to the other unless it moves faster than light, classical realism commits the fallacy of simple location. Thus it assumes that because the observation is theoretically represented as resulting from the interaction of the measuring apparatus with a particle that is simply located at the same point in space as the apparatus, the entity observed in this interaction is in fact a substance possessing the property of existing at that point in space; i.e., that it is simply located.

From within the framework of complementarity the "reality" producing the phenomena we call "observations" is represented by the wave function which defines the state of the system within the quantum formalism. This representation of the state of the system isolated from interaction may in principle be spread across an arbitrarily large area of space. The initial conditions which define this wave function are given by the state of the combined system of two protons while interacting in the singlet state. After the interaction we can consider each proton as a separate entity, but in doing so we are dealing with an abstraction that enables us to describe the interaction with the spin detector that forms the observation. This representation cannot, however, be regarded as a picture of the underlying reality. If we do so regard it, the experimental disconfirmation of Bell’s inequality forces us to conclude that some superluminary transmission of a causal relation connects the one simply located proton with the other. But no such strange conception of causal connection need be assumed, for there is no reason -- except dogmatic adherence to the classical framework -- to regard the quantum system as in any sense simply located. The property of location belongs to the causal mode of description; i.e., we attribute position in space to objects which we observe. Bohr called these objects phenomenal objects. Considered as an object of description, the phenomenal object "possesses simply location. However, this fact does not legitimize the conclusion that the object itself apart from the interaction has the property of simple location any more than a molecule considered in isolation has temperature.

When we do talk about the trajectories of particles or waves moving through free space, we do so in the context of an abstraction which is the goal of the mode of space-time coordination and is necessary for describing interactions through the causal mode. But we cannot regard this abstraction as a "picture" of the real entity without committing the fallacy of misplaced concreteness. The conclusions of Whitehead’s critique thus find confirmation in complementarity’s analysis of the disconfirmation of Hell’s inequality. But what of the reality which interacts with observing systems to produce the phenomena that quantum theory describes; what does the new framework tell us about this reality? Can it even support any realistic claims?

4. Conclusion -- The Nature of Quantum Mechanical Reality

The fundamental problem in providing an account of the nature of quantum mechanical reality requires devising a framework justifying the claim that quantum theory provides a complete description of reality and at the same time avoiding the paradoxes that arise when the quantum theory is viewed from within the framework of classical realism. How can we revise the notion of "physical reality" so that we can be scientific realists and accept the completeness of the quantum description of its objects?

Realism presents a descriptive ideal for science: we are to consider a scientific description "complete" or "adequate" only when it permits determining all of the properties possessed by the real entities which cause the experiences that confirm that particular theoretical representation. If we believe that we know what those properties are, we may ask of a theoretical description quite simply, does it allow determination of such properties or not? If it does not and yet science retains such a theory as acceptable, it would seem that science abandons realism. This was in fact Einstein’s conclusion about those who accepted the completeness of quantum theory.

As long as the received view dominated philosophy of science, it was believed that since our only foundation for accepting a theory is the experimental confirmation of that theory’s deductive consequences, the task of a theory was merely to permit deductions of statements describing experimentally observed phenomena, not to account for the character of reality. Hence, imposing the demands of a realistic metaphysics on scientific explanation seemed totally unjustified. However, we have now come to recognize the crucial role of the framework within which a theory is offered in stipulating the sorts of entities described by the theory. Thus the question of realism again becomes one internal to a philosophical account of scientific explanation, rather than an external metaphysical appendage which may be removed without any deleterious consequences to scientific explanation. The point of mentioning this new outlook is that the concept of reality cannot be regarded as given independently of scientific theory.7 This is what Einstein failed to appreciate with respect to quantum physics: scientific theory "informs" metaphysical frameworks. We may, of course, reject quantum physics and cling to the notion of reality implicit in the classical framework. But we have greater justification for regarding quantum theory as well established, and this fact indicates we must begin serious consideration of exactly what revisions in the framework and its concept of reality are required to regard this theoretical representation in a realistic way. The fact that a successful theory does not coincide with one concept of reality hardly entails that if we retain the theory, we have abandoned realism. What is required is a revised notion of reality.

With respect to this conclusion, Whitehead’s process philosophy and complementarity are in full agreement. Both recognize that simple location can no longer be considered a defining property of the ontologically real entity described by quantum physics. Since this property essentially defines "matter" as classically conceived, it is clear that realism and quantum mechanics can both be retained only once the ontology of classical materialism is fully relinquished. But the extent of this agreement between Whitehead’s outlook and complementarity goes beyond their common criticism of the classical framework. In stipulating that what is described by the state equations of quantum mechanics is not the properties of a substance but a process of interaction which cannot be unarbitrarily subdivided into separate physical systems in determinate states, the framework of complementarity essentially puts the notion of process at the heart of its characterization of the ontological status of the objects of experimental observation, or in other words, of experience.

No doubt, what these conclusions give us is not a framework itself, but an indication of some characteristics of a framework yet to be developed. The expectation that we can produce a unified, consistent framework within which the quantum description of reality can be realistically understood refers to an ideal goal rather than anything that is likely to be an historical fact. Looking backwards at the regime of classical mechanics, we often speak as though that stage of physics were dominated by a single consistent world-view. But this characterization is at least in part mythical, for, throughout the centuries from Newton to Einstein and Bohr, the framework of classical physics was always in a state of modification and in fact was never a single framework so much as a family of resembling variants with historical and conceptual linkages. Thus to expect that process philosophy can provide a single, unified, consistent framework within which the quantum description of reality can be interpreted realistically in a totally non-paradoxical manner is ill-founded and ahistorical. However, it is entirely defensible to argue that process metaphysics has injected into the career of philosophy crucial ontological conceptions, both critical and constructive, which may well serve as seeds from which a fuller understanding of the nature of the physical world, in both science and philosophy, may grow.



ATDN -- Niels Bohr. Atomic Theory and the Description of Nature. New York: Macmillan, 1934.

1. Henry J. Folse, Jr. "The Copenhagen Interpretation of Quantum Theory and Whitehead’s Philosophy of Organism," Tulane Studies in Philosophy 13 (1974), 32-47.



1 For example, cf. Abner Shimony, "Quantum Physics and the Philosophy of Whitehead," Boston Studies in the Philosophy of Science, vol. 2, ed. by Robert S. Cohen and Marx Wartofsky (New York: Humanities Press, 1965), pp. 307-30; Robert Palter, Whitehead’s Philosophy of Science (Chicago: University of Chicago Press, 1960), pp. 214-18; Milic Capek, Bergson and Modern Physics, Boston Studies in the Philosophy of Science. vol.7 (Dordrecht: D. Reidel, 1971), p.304f.; David Bohm, "The Implicate Order: A New Order for Physics," PS 8:73-102 (Summer, 1978); and (I -- see REFERENCES, above),

2A very clear ‘analysis of Bell’s theorem appears in Bernard d’Espagnat, "The Quantum Theory and Reality," Scientific America 241 (November, 1979), 158-81. Unfortunately, d’Espagnat draws conclusions from this analysis which do not seem fully warranted; cf. his exchange of letters with Victor F. Weiskopf, Scientific American 242 (May,1980) 8-10, as well as T. A. Brody and P. E. Hodgson., "Comment on d’Espagoat’s ‘Quantum Theory and Reality,’" Epistemological Letters 62.0 (April, 1981), 7f.; and H. D. Zeh The Problem of Conscious Observation in Quantum Mechanical Description, Epistemological Letters 63.0 (July, 1981), 1-12.

3 Henry Pierce Stapp, "Quantum Mechanics, Local Causality, and Process Philosophy," ed. by William B. Jones, PS 7:172-82 (Fall, 1977); Charles Hartshorne, "Bell’s Theorem and Stapp’s Revised View of Space-Time," PS 7:183-91 (Fall, 1977); and William B. Jones, "Bell’s Theorem, H. P. Stapp, and Process Theism," PS 7:250-61 (Winter, 1977).

4 The constraints of a journal article make this overview is necessarily brief; a full account of my interpretation of complementarity and an analysis of how Bohr arrived at his views will appear in Henry J. Folse, The Framework of Complementarity, forthcoming. Cf. also my articles, "Complementarity and the Description of Experience, International Philosophical Quarterly 17/4 Dec., 1977), 377-92, and "The Formal Objectivity of Quantum Mechanical Systems," Dialectica 29/2 (1975), 127-43.

5A complete survey of these developments in philosophy of science is given by Frederick Suppe in, "The Search for Philosophic Understanding of Scientific Theories" and "Afterword -- 1977" in The Structure of Scientific Theories, second edition, ed. by F. Suppe (Urbana: University of Illinois Press, 1977), pp. 3-241 and 617-730.

6These aspects of the framework are discussed in my article, "Rationality and the Ideal of the Description of Nature," Section Papers: 16th World Congress of Philosophy (Dusseldorf, 1978), 243-46.

7This notion of the relation between the findings of science and the task of philosophy is developed by C. A. Hooker, "Systematic Realism," Synthese 26, 414f. Cf. also my article "Belief and the New Scientific Realism," Tulane Studies in Philosophy, Fall, 1981.