63

p The question of physical reality arose and was developed in modern physics. In classical physics it was never actually formulated, or rather, it coincided with the question of objective reality. If the concept of physical reality was used in classical physics at all, it meant nothing other than acceptance of the objective reality of the physical world, which developed in accordance with one and the same invariable laws. Why, as we shall now see, has the question of physical reality now acquired special significance in arguments of a philosophical character about the theory of relativity and quantum theory?

p The most important reason is that the phenomena and processes with which the modern physics is concerned are covered by its theories by means of methods and abstractions that appear strange from the point of view of the notions of classical physics. No physicist has ever seen an electron as he sees, say, a stone rolling down a mountain, or a sea wave. Ultraviolet light, however, is also invisible to man, and there are sounds that cannot be heard, but in these cases no special questions arise!

p To put it briefly, let us recall simply that the observed phenomena by which the physicist forms judgements (draws inferences) about the electron and its motion in the atom, about the atomic nucleus, or, let us say, about objects moving with velocities close to the speed of light, create paradoxical theoretical situations in physics when it is attempted to interpret them in terms of the ideas and schemes of classical theories.

p Generally speaking, modern physics does not generalise everyday experience but the experience pertaining to very refined phenomena that do not fit into classical physics’ notions about nature. In such a refined experiment, for which high precision instruments are used, the physical facts are grasped by the cognising mind in a very complex way, through concepts, of very different levels of abstraction (that appear strange from the angle of classical physics). As an example we can take the discovery of resonances (as extremely unstable elementary particles with a halflife of 10 ^^23^^ second are called), which could not have been 64 done without a whole chain of theoretical considerations that have nothing in common with classical ideas.  [64•* 

p [So the physicist, who is not prepared to discard his belief in the objective reality of the external world and its knowability by man, becomes an eye-witness of the following situation: objective reality seems to escape cognition, while the concepts which, if one can so express it, helped to cognise the physical world, now refuse to serve. In Einstein’s theory of relativity, for instance, space and time proved relative in contrast to the corresponding concepts of classical physics, according to which space and time are absolute. In quantum mechanics, in accordance with its central idea of. Bohr’s complementarity, something similar happened with the terms ‘particle’ and ‘wave’, which lost their significance of absolutes and acquired the sense, unusual for classical physics, of ’relativity to the means of observation’. The most typical feature of the relativistic quantum theory of elementary particles is the absence from it of the principle of constancy of the number of particles and recognition of the fact that particles appear and disappear during interaction.

p The fundamental propositions of modern physics are necessarily bizarre, strange, and unconventional from the point of view of common sense and classical theory.

p In the new circumstances of the development of physics of this kind the concept of physical reality (’the physically real’) began to acquire a new meaning for physicists that it did not have in classical science. In order to identify and determine this new element, let us first briefly consider statements about physical reality of the founders of modern physics.

p In Einstein and Infeld’s The Evolution of Physics we read: ’We have seen new realities created by the’advance of physics.’ ’Physics really began with the invention of mass, force and an inertial system. These concepts are all free inventions.’ ’For the physicist of the early nineteenth century, 65 the reality of our outer world consisted of particles with simple forces acting between them and depending only on the distance.’ ’The difficulties connected with the deflection of the magnetic needle, the difficulties connected with the structure of the ether, induced us to create a more subtle reality. The important invention of the electromagnetic field appears.’ ’Later developments both destroyed old concepts and created new ones. Absolute time and the inertial co-ordinate system were abandoned by the relativity theory.’ ’The quantum theory again created new and essential features of our reality.’ ’The reality created by modern physics is, indeed, far removed from the reality of the early days.’^^62^^

p It does not follow at all from these statements that Einstein denied the objective reality of the physical world and suggested that the physicist’s sole reality is allegedly his free inventions.

p We could have wished, of course, that Einstein’s remarks about reality have been more precise and unambiguous. There is no doubt that he adopted a materialist standpoint of recognising the objective reality of the external world cognised by physicists, although he did not always express it clearly and distinctly enough. Here, however, is an extract from his paper Quantum Mechanics and Reality, which no longer leaves any doubt: ’If one asks what are the typical features of the world of physical ideas, regardless of quantum theory, the following above all strikes one: physical concepts pertain to a real external world, i.e. they imply ideas about things that require a "real existence" (of a body, a field, etc.) that is independent of the perceiving subjects; on the other hand, these ideas are transformed to correspond as exactly as possible to the sensual impressions.’^^63^^

p We must recall that Einstein thought quantum mechanics (as understood by Bohr and Heisenberg) to be incompatible with the fundamentals of physics formulated by him. He opposed the Copenhagen interpretation of quantum mechanics, considered it (bearing in mind the philosophical aspects of the discussions that arose in his time) as positivistic, and suggested that a complete and direct description of reality would be found, which in his view quantum mechanics in Bohr’s interpretation did not give.

p This matter has been discussed in the literature^^64^^; without going into details, we shall simply note that Einstein 66 approached the physical meaning of quantum mechanics from the standpoint of the basic ideas of classical physics, i.e. in much the same way as his theory of relativity was approached by opponents of physical relativism. Let us return to his remarks about physical reality.

p In making his objections to Einstein, Born believed that the latter borrowed his point of view on physical concepts’ being free inventions of the human mind from conventionalists’ opinions on concepts.^^65^^ In fact, however, Einstein, in stating that physical concepts were free creations of human mind, was stressing (as he himself said) simply that they were ’not logically derivable from what is empirically given’.^^68^^ This is a profound dialectical thought: the transition from the perceived results of observation to theoretical judgements about the observed phenomena, and also to the theory of these phenomena itself, is not by any means made through logical inferences of a formal character. As a matter of fact, Born was also saying the same thing when he analysed the method of mathematical hypothesis and the synthetic forecasts associated with it.^^67^^

p What then was Born’s standpoint on physical reality? At bottom it did not differ from the views of Bohr and Heisenberg (which were considered in detail in sections 2 and 3).

p The main point of Born’s argument about physical reality is that this question should be approached in terms of the concept of invariance taken from mathematics.

p Born did not consider ’very apt’ a statement common in the literature in connection with Bohr’s ideas that it is impossible in quantum mechanics to speak of an objectively existing external world, or of a ’sharp distinction between subject and object’.^^68^^ At the same time, he said, ’the naive approach to the problem of reality which was so successful in the classical or Newtonian period, has proved to be not satisfactory’.^^69^^

p On the other hand, Born disagreed with positivists’ understanding of reality according to which the concept of reality was either applied to atoms and electrons with a meaning other than to perceptible phenomena or its use was forbidden in general in science (as, for instance, the British positivist Herbert Dingle poses the matter). The microscope makes it possible to observe colloidal particles, the electron microscope, even large molecules. ’Where does 67 that crude reality, in which the experimentalist lives, end, and where does the atomistic world, in which the idea of reality is illusion and anathema, begin?’ Born asked, criticising contemporary positivists.

p But although the boundary between the ’world of atoms’ and ’macroscopic reality’ established by positivism does not exist, they still differ from each other as quantum physics has demonstrated. Born asked whether ’any philosophy can give a definition of the concept of reality that is untainted’ by ’the realities of a peasant or craftsman, a merchant or banker, a statesman or soldier’.^^70^^ He answered his question positively and considered the key to it to be in the idea of invariance.

p Born gave an example from the ’pre-scientific field’: when a person sees a dog sitting beside him or jumping about or disappearing in the distance, all these different perceptions are unified in his subconsciousness as one and the same dog. ’I propose,’ he said, ’to express this by saying that the mind constructs, by an unconscious process, invariants of perception, and that these are what ordinary man calls real things.’^^71^^

p The same thing essentially happens, in Born’s opinion, at the level of scientific cognition when instruments are used. Here ’the innumerable possible observations are linked again by some permanent features, invariants, which differ from those of ordinary perception, but are nevertheless in the same way indicators of things, objects, particles’.^^72^^ In the theory of relativity, for example, such reality is the interval—the invariant of the spatial and temporal aspects; in quantum mechanics, the electrons and other atomic objects are the invariants of the corpuscular and wave aspects, which allows one to ascribe reality to them.

p The views of the American physicist Richard P. Feynman are close to Born’s opinions on the invariance. In the first volume of The Feynman Lectures on Physics, devoted to the special theory of relativity, one comes across various versions of the idea that the four-vector momentum is more ‘real’ than either the momentum or the energy alone, since the momentum (represented by the space components of the four-vector arrow) and the energy (represented by its time component) depend on the observer’s point of view, i.e. on the frame of reference.^^73^^ This statement does not differ essentially at all from the proposition (which can 68 often be met in the literature) that Minkowski’s interval is more real than its components—the spatial distance and the temporal duration.

p When this material on the views of physicists on physical reality is compared with the way the problem of reality was treated in the history of philosophy, points of intersection of the lines of development of the corresponding ideas can be found. Let us just sketch it briefly.

p {The concept of reality is usually not separated from the more general concept of being and coincides with the concept of existence in historically known systems of philosophy, including contemporary philosophical theories, the content of the reality concept bearing the stamps of the basic assumptions of the corresponding system. For our theme the idea of ’degree of reality’ first clearly formulated by scholastics, who ascribed the ’highest degree of reality’ to God, who possessed the whole ’completeness of being’, is important. In the fourteenth century dispute between the so-called realists and nominalists over the concept of reality occupied the foreground. The realists, whose conception originated in Plato’s principles of idealism, said universalia sunt realia, i.e. that the existence was inherent in the universal as independent being above and independent of the individual. The nominalists raised objections to the realists, who most fully expressed the traditional scholastic philosophy; in the nominalists’ view nothing existed in the real world except individual things that had certain general properties. Marx called nominalism ’the first form of materialism’.^^74^^

p The realist and nominalist concepts were reborn in the subsequent historical development of philosophical thought, including modern bourgeois philosophy. Without making the relevant analysis we shall simply note that the ideas of realism are also manifested in special form in modern physics in the works of certain scientists.

In every outstanding philosophical system of modern times, materialist and idealist, the idea of degree of reality has been expressed and developed in one form or another. It can be found in the systems of Descartes, and of Spinoza, according to whom substance possessed the highest degree of reality. Locke believed that the so-called primary qualities of things (length, impenetrability, motion) had a greater degree of reality than secondary ones (colour, sound, smell). 69 According to Leibniz monads had the highest degree of reality. Hume supposed that impressions, either renewed by the consciousness or stable, had a greater reality than any others. In Kant we find a distinction between the ’empirical reality’ of phenomena and categorial (abstract) reality. In his -Science of Logic Hegel differentiated reality (Realitat) from actuality (Wirklichkeit) as a unity of essence and existence, or of the internal and external. Contemporary bourgeois" philosophy (e.g. logical positivism, critical realism) contains nothing new, compared with classical philosophy, on the question of reality.

p Let us summarise what we have said about reality in physics and formulate certain statements relating to this concept that appear important to us.

p The terra ‘reality’ (the ‘real’) is used with several meanings. The most general of them is that of existence: the perceptible ball exists and the perception of the ball exists; a particle exists and a material point exists; a billiard ball exists and an ideal ball exists; an electron diffraction pattern exists and electron diffraction exists; matter exists and spirit exists; truth exists and error exists; they are all real in this sense of the term.

p There is a difference between the ‘real’ in the sense of existence and the ’objectively real’. The ’objectively real’ or the ‘objective’ or the ’objectively existing’ means existing independently of the human mind and reflected by it under certain conditions. In opposition to the objective the ’subjective’ means ’existing in consciousness’. The subjective or spiritual  [69•*  (sensations and perceptions, concepts, judgments, etc.) can and do reflect the objectively real in certain conditions. This subjective functions in scientific theories and science as a whole, which objectively reflect the real world; it therefore also figures in physics and its theories. The subjective, however, may not reflect the objectively real because of errors and illusions; it appertains to man’s subjective world. The natural sciences, of course, are not concerned with this world, or rather physics is concerned with material realities and not with spiritual ones. That is why, when we speak of ’the physical reality 70 of a certain something’, we mean that somehow or other the concept of this something does or should correspond to the objectively real.

p The term ‘real’ (‘reality’) has another meaning of the actual’ (or ‘actuality’). It derives from the Latin res (thing, object); while the term ‘actual’ comes from ‘act’ (Latin actus) (German wirklich from ivirken; Russian deistviteVnyi from deistvovaf). The concept ’physical reality’, as we shall see later, is closest of all to the concept ‘actuality’ ( Wirklichkeit) in content and meaning.

p The ‘existing’ and the ‘actual’ are by no means identical, and this difference is literally tangible in modern physics. With a Wilson cloud chamber, for instance, which was designed for observing the tracks of fast-moving, electrically-charged particles (electrons, protons, etc.), one can draw inferences about the nature and properties of these particles from the parameters of the visible tracks of their trajectories. But have we the right to infer from the data obtained that an electron moves ’in actuality’ in the way a macro-particle does? Quantum theory, as we know, has given an answer to that; and it follows from this answer that (1) the ‘existing’ and the ‘actual’ in physics are by no means the same; and (2) that every ’objectively real’ in physics is not thereby ‘actual’ in a certain theory, but every ‘actual’ in a physical theory is ’objectively real’.  [70•* 

p The question of physical reality, as it is considered at present, cannot be comprehended outside the ’ epistemological lesson’ (Bohr) that the development of modern physics has given scientists. What is the essence of this lesson? In classical physics the observed phenomena made it possible to obtain information (at least in principle) about the behaviour of objects regardless of their interaction with the means of observation (measuring instruments). In quantum physics the observed phenomena also provide information about the experimental conditions, which can no longer be ignored in principle, in other words, quantum phenomena characterise the properties of the ’whole experimental situation’ rather than those of the object ’by itself. In short, from the point of view of quantum physics the experimental physicist has proved to be, figuratively 71 speaking, not simply a spectator but an actor in the drama of cognition, so it is put in the literature on quantum theory as is well known. Hence corresponding problems of physical reality arose.

p It seems to us, however, that the content of the ’ epistemological lesson’ that Bohr spoke about is much broader. Classical science considered it its job to find the universal constant laws of nature. Modern physics has rejected such an approach from its very inception: classical mechanics is a limiting case of the special theory of relativity and quantum mechanics, i.e. of the more general and deeper theories; the special theory of relativity is the limiting case of Einstein’s theory of gravitation; quantum electrodynamics has developed and quantum field theory is being built; and ideas are voiced about the future of physics belonging to even more general and profound fundamental theories than those now existing. In other words, for modern physics it is essential not only to find the laws of the phenomena existing in a certain system (circle) of interrelations, but it is also important (this question arises sooner or later in one form or another at a certain stage of its development) to find the laws of the transition from the laws of one sphere of phenomena to the deeper, more general laws (which must and will be found) of a new, wider circle of phenomena.

p Modern physics thus undermined the prejudice of the old contemplative materialism, according to which cognition, i.e. reflection of nature by the human brain, should be understood ‘abstractly’, ’devoid of movement’, ’without contradiction’,^^75^^ a philosophical prejudice that in essence was supported by classical science. With the creation of the theory of relativity and quantum theory Lenin’s idea of cognition found expression in physics: ’Man cannot comprehend = reflect = mirror nature as a whole, in its completeness, its "immediate totality", he can only eternally come closer to this, creating abstractions, concepts, laws, a scientific picture of the world, etc., etc.’^^76^^

p That spatial and temporal quantities prove to be dependent in the theory of relativity on the frame of reference chosen by the observer, or that in quantum mechanics, in Bohr’s words, ’any observation of atomic phenomena will involve an interaction with the agency of observation not to be neglected’^^77^^ does not in the least mean that the theory of relativity and quantum mechanics in addition 72 to employing their principles and concepts allegedly imply some degree of subjectivity, some reference to the observing subject, some special activity of the observer. On the contrary, these and similar features, which are typical of the relativistic or quantum method of describing phenomena mean that the physical knowledge has penetrated deeper, that the new concepts and principles developed by modern physics reflect nature’s patterns more correctly and completely than those of classical theories.

p When we turn, say, to quantum mechanics, the wave and particle pictures of the behaviour of electrons  [72•*  observed through the appropriate set-up; the concept of relativity with respect to the means of observation plus the complementarity principle interpreted in the sense that only the aggregate of ‘complementary’ phenomena can provide complete information about the behaviour of a microobject; the concept of the electron as a physical substance possessing certain invariant characteristics; and the Schrodinger equation which is invariant with respect to unitary transformations—all these are levels of cognition of the moving electron which combine to form an integral theory embracing the experimental data.

p On this plane the concepts and statements of the quantum theory listed above reflect the objectively real. In exactly the same way ‘probability’ in quantum mechanics, mathematically represented by the square of the modulus of the wave functioa, is physically real, i.e. its physical concept reflects the objectively real and is by no means just a ‘pure’ construction of the physicist’s.

p These considerations concerning quantum mechanics, and similar arguments about Einstein’s theory (we neglect them here), have a direct bearing on the problem of physical reality. Construction of a theory of a certain circle of phenomena solves the problem of the reproduction in thought of the object of this theory as it exists in actuality, i.e. as a concrete integrity of phenomena and substance (the causal relation, basic laws), of the external and the internal, or as a unity of the diverse.

p The construction of a theory provides the most complete knowledge of its object, and from that point of view, if we 73 consider the examples above, physicists’ statements that the space-time continuum is ’more real’ than either space or time separately, are logically justified.

p From the same point of view the hypertrophy of any one aspect of the cognition of something, and neglect of the fact that unity exists in its many-sidedness, leads in the final analysis to subjectivism and conclusions of an idealist and metaphysical character. A similar situation arises in the theory of relativity if ‘relativity’ is absolutised and one is abstracted from the fact that space and time are aspects of a single space-time.^^78^^ An analogous situation arises in quantum theory when the idea of interaction of atomic objects and the measuring instruments (which causes the ’uncontrollability in principle’) is overemphasised and it is forgotten that complementary experiments ’only in combination with each other disclose all that can be learned about an object’.^^79^^

p In connection with what has been said one cannot help agreeing with Bohr who raised objections to Heisenberg and Dirac on how one should speak of the emergence of phenomena that permitted only predictions of a statistical character. According to Dirac, we are dealing here with choice by ‘nature’ when the point in question is the realisation of one individual effect (from the number of possible ones); according to Heisenberg, with choice by the ‘observer’ who built the measuring instruments and took the readings. ’Any such terminology,’ Bohr said, ’would, however, appear dubious since, on the one hand, it is hardly reasonable to endow nature with volition in the ordinary sense, while, on the other hand, it is certainly not possible for the observer to influence the events which may appear under the conditions he has arranged.’ Bohr believed that ’there is no other alternative than to admit that, in this field of experience, we are dealing with individual phenomena and that our possibilities of handling the measuring instruments allow us only to make a choice between the different complementary types of phenomena we want to study’.^^80^^

p The rise of new relative concepts in science, and at the same time of new, more profound and more general theories in which they figure (e.g. the concepts of relative space and time in the theory of relativity, which is a new theory in regard to classical physics) does not mean the increase in elements of subjectivity (since the new types of reference 74 system appear that have not been known before); it means a new step in understanding nature. Indeed, first, the new relative concepts reflect the objectively real; second, the appearance of new ‘relativities’, more meaningful than those known before, means the finding of limits of applicability of the absolute (invariant) concepts of the old theory (from which the new one was developed).

p The concept of physical reality thus comes into modern physical literature also as a kind of synonym of the philosophical concept of actuality in the sense of dialectical materialism. It seems to us that it is logically legitimate to employ the terms ’empirically real’ (’empirical reality’) and ’abstractly real’ (’abstract reality’). The first of these denotes that which exists independently of the human mind (the objectively real) and is embraced by that stage of cognition which is called living contemplation and without which there can be no observation. The second term denotes the objective reality that is reflected at a deeper level of human understanding—the abstract thinking that reveals the essence of cognised phenomena, the laws of nature. But the deepest and the most complete cognition of an object that exists independently of the human mind is achieved by combining observation and abstract thinking (we could rightly use the term ’dialectical thinking’ here) when a scientific theory reflecting its object as reality, i.e. as a united whole of numerous aspects and their relations, is constructed logically on the basis of practice and acquires certain integrity and relative validity.

p Physical reality is thus the objective reality cognised in a physical theory, the content of the concept of which becomes definite depending on the definiteness of the theory itself as such and the stages (elements) of its structure.

p REFERENCES

p  ^^1^^ See Max Born. Symbol und Wirklichkeit. Physikalische Blatter, 1964, 20, 12; 1965, 21, 2: 53-63; 3: 106-108.

p  ^^2^^ See references in Chapter V on dialectical contradictoriness in modern physics.

p  ^^3^^ See, for instance, Einstein’s Autobiographical Notes in Albert Einstein: Philosopher-Scientist. Edited by P. A. Schilpp (Tudor Publishing Co., New York, 1951), pp 5-9; Niels Bohr. Atomic Physics and Human Knowledge (John Wiley & Sons, New^York, Chapman & Hall, London, 1958); Max Born. Physical Reality. In: Max Born. Physics 75 in my Generation (Pergamon Press, London & N. Y., 1956), pp 151- 163; H. Margenau. The Nature of Physical Reality. A Philosophy of Modern Physics (McGraw-Hill Book Company, New York, Toronto, London, 1950), pp 5, 51.

p  ^^4^^ V. I. Lenin. Materialism and Empirio-criticism. Collected Works, Vol. 14 (Progress Publishers, Moscow), p 262.

p  ^^6^^ Ibid., p 261.

p  ^^6^^ Rudolf Carnap. Meaning and Necessity. A Study in Semantic and Modal Logic (Univ. of Chicago Press, Chicago, 1956), p 207.

p  ^^7^^ V. I. Lenin, Op. cit., p 189.

p  ^^8^^ Ibid., pp 126-127.

p  ^^9^^ Max Born. Symbol und Wirklichkeit. Physikalische Blatter, 1965, 21, 2: 59.

p  ^^10^^ Ibid.

p  ^^11^^ Max Born. Physics in my Generation, pp 151-163.

p  ^^12^^ Max Born. Symbol und Wirklichkeit. Physikalische Blatter, 1965, 21, 3: 107-108.

p  ^^13^^ Henry Margenau. Op. cit., pp 5, 51, 85, 457.

p  ^^14^^ Ibid., p 9.

p  ^^16^^ Max Born. Physics in my Generation, p 106.

p  ^^16^^ V. I. Lenin, Op. cit., p 246.

p  ^^17^^ Niels Bohr. Op. cit., p 91.

p  ^^18^^ See below in the last two sections of Chapter IX.

p  ^^19^^ V. I. Lenin. Philosophical Notebooks. Collected Works, Vol. 38 (Progress Publishers, Moscow), p 98.

p  ^^20^^ Werner Heisenberg. Der Tell und das Ganze (Piper & Co., Munich’ 1969), p 124; idem. Gesprache iiber das Verhaltnis von Naturwissen" schaft und Religion. Physikalische Blatter, 1970, 26, 7: 294.

p  ^^21^^ Werner Heisenberg. Physics and Philosophy (George Allen & Unwin, London, 1959), p 46.

p  ^^22^^ Ibid., p 50.

p  ^^23^^ Ibid., p 52.

p  ^^24^^ Ibid., pp 57, 75.

p  ^^25^^ Ibid., p 56.

p  ^^26^^ Ibid., p 83.

p  ^^27^^ Ibid., p 55.

p  ^^38^^ On relativity to the conditions (or means) of observation, see V. A. Fock. Quantum Physics and the Structure of Matter. In: M. E. Omelyanovsky (Ed.). Struktura I formy materii (Nauka Publishers, Moscow, 1967).

p 28 Werner Heisenberg. Physics and Philosophy, pp 95-96.

p  ^^30^^ V. I. Lenin. Philosophical Notebooks. Op. cit., p 208.

p  ^^31^^ Niels Bohr. Essays 1958-1962 on Atomic Physics and Human Knowledge (N.Y., London, Interscience Publ., 1963), p 5.

p  ^^32^^ Ibid., p 6.

p 33 Ibid., p 4.

76

p  ^^34^^ Niels Bohr. Op. cit.

p  ^^35^^ Ibid., p 4.

p  ^^36^^ Ibid., p 3.

p  ^^37^^ Ibid., p 5.

p  ^^38^^ /6W., p 5.

p  ^^39^^ Ibid., p 6.

p  ^^40^^ H. Reichenbach. Tfee Direction of Time (Univ. of Gal. Press, Berkeley & Los Angeles, 1956), pp 216-217.

p  ^^41^^ Ibid., p 217.

p  ^^42^^ Ibid., p 218.

p  ^^43^^ 76id., pp 217, 218.

p  ^^44^^ Werner Heisenberg. Physics and Philosophy, p 55.

p  ^^45^^ This paper was first published in Uspekhi fizicheskikh nauk, 1951, 45, 1. It was republished in a revised, expanded form in the Czechoslovak Physics Journal, 1955, 5, 4. A nearly identical text was published in the symposium Filosofskie voprosy sovremennoi fiziki ( Philosophical Issues of Modern Physics) (Gospolitizdat, Moscow, 1958).

p  ^^46^^ V. I. Lenin. Materialism and Empirio-criticism. Op. cit., p 262.

p  ^^47^^ W. von Pauli. Wahrscheinlichkeit und Physik. Dialectica, 1954, 8, 3: 118.

p  ^^48^^ Werner Heisenberg. Die Plancksche Entdeckung und philosophischen Grundfragen der Atomlehre. Naturwissenschaften, 1958, 45, 10: 230.

p  ^^49^^ Niels Bohr. Atomic Physics and Human Knowledge, pp 50-51.

p  ^^50^^ V. A. Fock. Comments on Bohr’s Paper About His Discussions with Einstein. Uspekhi fizicheskikh nauk, 1958, 66, 4: 600.

p  ^^61^^ Werner Heisenberg. Physics and Philosophy, pp 127-128.

p  ^^62^^ Ibid., p <°°

p 63 Werner Heisenberg. Op. cit. M Ib id., p 114.

p  ^^65^^ Ibid., p 115.

p  ^^66^^ V. A. Fock. Op. cit., pp 599-600.

p  ^^67^^ Werner Heisenberg. Physics and Philosophy, p 123.

p  ^^88^^ Werner Heisenberg. The Development of the Interpretation of the Quantum Theory. In: W. von Pauli (Ed.). Niels Bohr and the Development of Physics (Pergamon Press, London, 1955), p 28.

p  ^^58^^ Werner Heisenberg. Physics and Philosophy, p 139.

p  ^^60^^ Ibid.

p  ^^61^^ See Auffassungen iiber die Quantentheorie. Physikalische Blatter, 1969, 25, 3: 105-113.

p  ^^62^^ Albert Einstein and Leopold Infeld. The Evolution of Physics (Simon & Schuster, New York, 1942), pp 310-312.

p  ^^63^^ Albert Einstein. Quanten-Mechanik und Wirklichkeit. Dialectica, 1948, 2, 3/4: 321.

p  ^^64^^ Niels Bohr. Atomic Physics and Human Knowledge, pp 32-66; see also V. A. Fock. Quantum Physics and the Structure of Matter. In: M. E. Omelyanovsky (Ed.). Struktura i formy materii (Op. cit.).

77

p ^d6 Max Born. Physics in my Generation, p 105.

p  ^^66^^ See P. A. Schilpp (Ed.). Albert Einstein. Philosopher-Scientist, p 684.

p  ^^67^^ Max Born. Experiment and Theory in Physics (CUP, Cambridge, 1944), pp 10-14.

p  ^^68^^ Max Born. Physics in my Generation, p 105.

p  ^^69^^ Ibid., p 152.

p  ^^70^^ Max Born. Physikalische Wirklichkeit. Physikalische Blatter. 1954, 10, 2: 51; see also: idem. Physics in my Generation, pp 152-153.

p  ^^71^^ Max Born. Physics in’my Generation, p 105. Born expressed similar ideas in several of the papers of this collection.

p  ^^72^^ Ibid., p 105.

p  ^^73^^ R. P. Feynman, R. B. Leighton, and Matthew Sands. The Feynman Lectures on Physics, Vol. I (Addison-Wesley Publ. Co., Reading, Mass., 1963), p 17.

p  ^^74^^ Karl Marx and Frederick Engels. The Holy Family. Collected Works, Vol. 4 (Progress Publishers, Moscow, 1975), p 127.

p  ^^75^^ The words in inverted commas are from Lenin’s remarks in the Philosophical Notebooks (Collected Works, Vol. 38, p 195).

p  ^^76^^ Ib id., p 182.

p  ^^77^^ Niels Bohr. The Quantum Postulate and the Recent Development of Atomic Theory. Supplement to Nature, 1928, 121, 14 April: 580.

p  ^^78^^ A. D. Alexandrov demonstrated this beautifully in his paper Space and Time in Modern Physics in the Light of Lenin’s Philosophical Ideas in: M. E. Omelyanovsky (Ed.). Lenin and Modern Natural Science (Progress Publishers, Moscow, 1978).

p  ^^79^^ Max Born. Physics in my Generation, p 187.

 ^^80^^ Niels Bohr. Atomic Physics and Human Knowledge, p 51.