Theory-building quotes from Bohr, Pauli, Heisenberg, Husserl, and Stapp
Niels Bohr, 'Atomic Theory and the Description of Nature', pp. 100 (passage referenced by von Neumann as his source for the principle of the psycho-physical parallelism), 116-7 (similar passage where the term 'parallelism' is actually used):
When considering the contrast between the feeling of free will, which governs the psychic life, and the apparently uninterrupted causal chain accompanying physiological processes, the thought has, indeed, not eluded philosophers that we may be concerned here with an unvisualizable relation of complementarity. Thus, the opinion has often been expressed that a detailed investigation of the processes of the brain, which, although not practicable, is nevertheless, thinkable, would reveal a causal chain that formed a unique representation of the emotional mental experience. However, such an idealized experiment now appears in a new light, since we have learned, by the discovery of the quantum of action, that a detailed causal tracing of atomic processes is impossible and that any attempt to acquire knowledge of such processes involves a fundamentally uncontrollable interference with their course. According to the above-mentioned view on the relation between the processes in the brain and the psychical experiences, we must, therefore, be prepared to accept the fact that an attempt to observe the former will bring about an essential alteration in the awareness of volition. Although, in the present case, we can be concerned only with more or less fitting analogies, yet we can hardly escape the conviction that in the facts which are revealed to us by the quantum theory and lie outside the domain of our ordinary forms of perception we have acquired a means of elucidating general philosophical problems.
Hoping that I do not expose myself to the misunderstanding that it is my intention to introduce a mysticism which is incompatible with the spirit of natural science, I may perhaps in this connection remind you of the peculiar parallelism between the renewed discussion of the validity of the principle of causality and the discussion of a free will which has persisted from earliest times. Just as the freedom of the will is an experiential category of our psychic life, causality may be considered as a mode of perception by which we reduce our sense impressions to order. At the same time, however, we are concerned in both cases with idealizations whose natural limitations are open to investigation and which depend upon one another in the sense that the feeling of volition and the demand for causality are equally indispensable elements in the relation between subject and object which forms the core of the problem of knowledge.
Wolfgang Pauli, 'Writings on Physics and Philosophy', pp. 260-1, 225, 232, 239:
Furthermore, whereas older philosophical systems have located the psychical on the subjective side of the division, that is, on the side of the apprehending subject, and the material on the other side - the side of that which is objectively observed - the modern point of view is more liberal in this respect: microphysics shows that the means of observation can also consist of apparatuses that register automatically; modern psychology proves that there is on the side of that which is observed introspectively an unconscious psyche of considerable objective reality. Thereby the presumed objective order of nature is, on the one hand, relativized with respect to the no less indispensable means of observation outside the observed system; and, on the other hand, placed beyond the distinction of 'physical' and 'psychical'.
Now there is a big difference between the observers, or instruments of observation, which must be taken into consideration by modern microphysics, and the detached observer of classical physics. By the latter I mean one who is not necessarily without effect on the system observed but whose influence can always be eliminated by determinable corrections. In microphysics, however, the natural laws are of such a kind that every bit of knowledge gained from a measurement must be paid for by the loss of other, complementary items of knowledge. Every observation, therefore, interferes on an indeterminable scale both with the instruments of observation and with the system observed and interrupts the causal connection of the phenomena preceding it with those following it. This uncontrollable interaction between observer and system observed, taking place in every process of measurement, invalidates the deterministic conception of the phenomena assumed in classical physics: the series of events taking place according to pre-determined rules is interrupted, after a free choice has been made by the beholder between mutually exclusive experimental arrangements, by the selective observation which, as an essentially non-automatic occurrence (Geschehen), may be compared to a creation in the microcosm or even to a transmutation (Wandlung) the results of which are, however, unpredictable and beyond human control.
In this way the role of the observer in modern physics is satisfactorily accounted for. The reaction of the knowledge gained on the gainer of that knowledge (Erkennenden) gives rise, however, to a situation transcending natural science, since it is necessary for the sake of completeness of the experience connected therewith that it should have an obligatory force for the researcher (fur den Erkennenden verbindlich). This connection can only be comprehended through symbols which both imaginatively express the emotional aspect of the experience and stand in vital relationship to the sum total of contemporary knowledge and the actual process of cognition. Just because in our times the possibility of such symbolism has become an alien idea, it may be considered especially interesting to examine another age to which the concepts of what is now called classical scientific mechanics were foreign but which permits us to prove the existence of a symbol that had, simultaneously, a religious and a scientific function.
Now for *Kepler* the most beautiful image, the one that represents God's own form of being (*idea ipsius essentiae*), is the three-dimensional sphere. He says already in his early work the *Mysterium cosmographicum*: "*The image of the triune God is in the spherical surface, that is to say, the Father's in the center, the Son's in the outer surface, and the Holy Ghost's in the equality of relation between point and circumference*".3 The movement or emanation passing from the center to the outer surface is for him the symbol of creation, while the curved outer surface itself is supposed to represent the eternal Being of God. Of the magnitudes (*quanta* or *quantitates*) evolved in the beginning by the Creator the curved one is the symbol of the intellectual or spiritual and is thus more perfect than the straight, which as the simulacrum of the created represents the physical world.
3 *Joannis Kepleri Astronomi Opera omnia, ed. by Ch. Frisch (8 volums, Frankfort on the Main and Erlangen, 1858 ff.), Volume I, pp. 122f.
From this example it can be seen that in *Kepler* the symbolical picture precedes the conscious formulation of a natural law. The symbolical images and archetypal conceptions are what cause him to seek natural laws. For this reason we also regard *Kepler*'s view of the correspondence between the sun with its surrounding planets and his abstract spherical picture of the Trinity as primary: *because he looks at the sun and the planets with this archetypal image in the background he believes with religious fervor in the heliocentric system* - by no means the other way around, as a rationalistic view might cause one erroneously to assume.
The human soul, in *Kepler*'s view, flows at birth into a pre-existent form, which is shaped on the earth by these rays of light from the stars (planets). Cf. the *Tertius interveniens*, No. 107:
For it is by no means to be pronounced foolishness that man is *naturali necessitate* diversified and qualified in accordance with the *Configarationibus stellarum*; this might really far rather be called an 'influence' of the nature of man into the star (as of fluid plaster into a mould) than, on the contrary, an 'influence' of the star into man.
Wolfgang Pauli, 'Writings on Physics and Philosophy', p. 34 (Letter from Pauli to Ralph Kronig, 12/22/49, published in 'Man's Right to Knowledge', 2nd Series, p. 10, 1954):
This means that one member of the pair is never eliminated in favor of the other, but both are taken over into a new kind of physical law which expresses properly the complementary character of the contrast.
It seems to me likely that the situation is similar in the case of the concepts of field versus test bodies. A field can only be measured by its effects on test bodies, and the test bodies can also be considered as sources of the field. This does not give rise to difficulties for the ordinary large scale, or macroscopic, phenomena, since the disturbance of the field by the test bodies can here always be supposed to be small and kept under control. This is, however, no longer the case for test bodies, the atomic constitution of which is essential, and particularly not for the elementary particles like the electrons or nucleons themselves, the location and motion of which is no longer under control as with macroscopic test bodies.
While in the present theory there exists still a duality between the concepts of fields and of test bodies, I think that a new mathematical form of the physical laws is required, which makes fields without test bodies not only physically but also logically impossible. It must also express properly the complementarity between the measurement of a field with an atomic object on the one hand, and the description of the same object as source of the field on the other hand. Indeed, these two possibilities should become automatically mutually exclusive as a result of a suitable form of the laws of nature.
Werner Heisenberg, 'Physics and Beyond', page 213:
A few hundred yards away, a large liner was gliding past, and in bright lights looked quite fabulous and unreal in the bright blue dusk. For a few moments, I speculated about the human destinies being played out behind the lit-up cabin windows, and suddenly Wolfgang's questions [about positivism] got mixed up with it all. What precisely was this steamer? Was it a mass of iron with a central power station and electric lights? Was it the expression of human intentions, a form resulting from interhuman relations? Or was it a consequence of biological laws, exerting their formative powers not merely on protein molecules but also on steel and electric currents? Did the word 'intention' reflect the existence merely of these formative powers or of these biological laws in the human consciousness? And what did the word 'merely' mean in this context?
My silent soliloquy now turned to more general questions. Was it utterly absurd to seek behind the ordering structures of this world a 'consciousness' whose 'intentions' were these very structures? Of course, even to put this question was an anthropomorphic lapse, since the word 'consciousness' was, after all, based purely on human experience, and ought therefore to be restricted to the human realm. But in that case we would also be wrong to speak of animal consciousness, when we have a strong feeling that we can do so significantly. We sense that the meaning of 'consciousness' becomes wider and at the same time vaguer if we try to apply it outside the human realm.
Werner Heisenberg, 'Across the Frontier', pages 219-220:
At this point we also recognize the characteristic difference between genuine religions, in which the spiritual realm, the central spiritual order of things, plays a decisive part, and the narrower forms of thought, especially in our own day, which relate only to the strictly experiencable pattern of a human community. Such forms of thought exist in the liberal democracies of the West no less than in the totalitarian states of the East. Here, too, to be sure an ethic is formulated, but the talk is of a norm of ethical behavior, and this norm is derived from a world outlook, that is, from inspection of the immediately visible world of experience. Religion proper speaks not of norms, however, but of guiding ideals, by which we should govern our conduct and which we can at best only approximate. These ideals to not spring from inspection of the immediately visible world but from the region of the structures lying behind it, which Plato spoke of as the world of Ideas, and concerning which we are told in the Bible, 'God is a spirit'.
Heisenberg, 'Physics and Philosophy', pages 54-55:
Therefore, the transition from the 'possible' to the 'actual' takes place during the act of observation. If we want to describe what happens in an atomic event, we have to realize that the word 'happens' can apply only to the observation, not to the state of affairs between two observations. It applies to the physical, not the psychical act of observation, and we may say that the transition from the 'possible' to the 'actual' takes place as soon as the interaction of the object with the measuring device, and thereby the rest of the world, has come into play; it is not connected with the act of registration of the result by the mind of the observer. The discontinuous change in the probability function, however, takes place with the act of registration, because it is the discontinuous change of our knowledge in the instant of registration that has its image in the discontinuous change of the probability function.
Certainly quantum theory does not contain genuine subjective features, it does not introduce the mind of the physicist as a part of the atomic event.
Edmund Husserl, 'Crisis of European Sciences', p. 153:
How can we make it more concretely understandable that the reduction of mankind to the phenomenon 'mankind', which is included as part of the reduction of the world, makes it possible to recognize mankind as a self-objectification of transcendental subjectivity which is always functioning ultimately and is thus 'absolute'? How does it become possible, thanks to the epoche, to display this subjectivity in its accomplishment, in its transcendental 'conscious life', extending into hidden subsoils, in the distinct manners in which it 'brings about', within itself, the world as ontic meaning? How can we bring this to light with self-evidence, not inventing or mythically constructing? If this is a matter of a new sort of scientific discipline, of a new sort of theoretical questioning and resolving of questions, then the ground for these questions, too, must be prepared. Natural questions about the world have their ground in the pregiven world of actual and possible experiences. And the gaze made free by the epoche must likewise be, in its own way, an experiencing gaze. [But] the accomplishment of the total transformation of attitude must consist in the fact that the infinity of actual and possible world-experience transforms itself into the infinity of actual and possible 'transcendental experiences', in which, as a first step, the world and the natural experience of it are experienced as 'phenomenon'.
Henry Stapp, 'On the Unification of Quantum Theory and Classical Physics' in 'Symposium on the Foundations of Modern Physics', 1985, World Scientific, pgs. 216-7, 219-21:
Heisenberg's idea of external reality is different from the one brought to mind by classical physics. Instead of a deterministic continuous evolution that eventually fills the entire spacetime continuum with a continuous microscopic picture of the history of the world, one has discrete happenings. These events are transitions from the 'possible' to the 'actual', and they occur only under special macroscopic conditions.
Von Weizsacker has emphasized to me that this picture of external reality described by Heisenberg is in general accord with the ideas of Bohr. I shall therefore call it the Copenhagen interpretation idea of external reality.
If quantum theory is to be extended into the domain of science where the idealized division of the physical world into the object and agencies of measurement is no longer possible then it is likely that a representation of external reality will need to be introduced into the formalism. Among the possible conceptions of external reality a prime candidate is the one of Bohr and Heisenberg. This conception is in general accord with the ideas of orthodox quantum theorists, and, we shall see, it can be brought into conformity with the principal demands of Einstein.
According to Bohr, the measurements we make can be described in terms of classical physical concepts. To bring the contemplated extension of quantum theory into ideal alignment with the ideas of Bohr and Heisenberg the transition from the 'possible' to the 'actual' should create realities that can be described in terms of the concepts of classical physics. This would resolve the basic puzzle of quantum theory, which is: why can the observable phenomena be described in terms of the concepts of classical physics?
To account for the detailed success of the concepts of classical physics in the domain of classical physics, within the framework of the Copenhagen-interpretation idea of external reality, it would seem that the transition from the 'possible' to the 'actual' should bring into being some ingredient of the classical description of nature. The foregoing section suggests that this ingredient should be some aspect or component of the classical electromagnetic field. The happening, or macroevent, would then be analogous to what occurs in a measurement situation, where some classically describable result appears. However the pertinence of the concepts of classical physics would now not be tied to human observers, but would arise from the presence in external reality, as represented in our theory, of the appropriate classical quantities.
The history of classical physics suggests that the concepts of classical physics correspond to aspects of nature that do not depend on their being observed by somebody. An ideal physical theory should reflect this fact by allowing the classical features to be independent of observers. The present proposal conforms to this ideal. However, it is based upon the Copenhagen-interpretation idea of external reality. It also conforms to Einstein's demand that basic physical theory represent the real external situation,11] and that this reality be represented by functions defined on the spacetime continuum.12]
Technical details pertaining to the elaboration of the general program outlined above can be found elsewhere.13],14]
11. A. Einstein, in 'Albert Einstein: Philosopher-Scientist', ed. P.A. Schlipp (Tudor Pub. Co., New York, 1949) pp. 667, 674.
12. Ibid. p. 675.
13. H.P. Stapp, Light as Foundation of Being, Lawrence Berkeley Laboratory report LBL-19144 (1985) (to appear in a Festschrift honoring David Bohm).
14. H.P. Stapp in proceeding of conference 'Microphysical Reality and Quantum Formalism -- Perspectives on the Einstein-Bohr Debate Fifty Years After the EPR Argument', to be held at the University of Urbino, Urbino, Italy, Sept. 25 - Oct. 3, 1985.