p In dealing with the connection between the phenomena of nature and its regularity, necessity, and causality, there are, as Lenin pointed out, two major philosophical lines, materialist and idealist. Recognition of the objective reality of the phenomena of nature and of the external world leads to recognition of an objectively real connection, necessity, causality, and determinacy in natural phenomena, i.e. materialism, which, when consistently followed, cannot be separated from determinacy. On the other hand, a consistently followed negation of the objective reality of the external world; and acceptance of nature as derived from mind, consciousness, and experience leads to a view that consciousness ‘creates’ laws, and mind introduces order into nature’s ’primary chaos’, and leads to acceptance of indeterminism, i.e. idealism, which, when it is consistent, is inseparably connected with indeterminism.

p It is not by chance that those scientists who tend toward idealism, i.e. who see only symbols, signs, and logical constructions serving to ’systematise the observed’ in scientific concepts and theories, instead of a reflection of objective reality, conclude that determinism either plays no scientific role whatsoever or has only limited significance as regards cognition of nature and that the principle of causality operates only in the sphere of the ideal, which has no relation to the real world. Ideas like this have been turned into whole philosophical conceptions in the work 143 of modern bourgeois philosophers^^1^^ as a reaction to physics having penetrated into the atomic and subatomic worlds, and having begun to study processes that are not perceived directly but are learned about only from the readings of instruments, statements about these readings, moreover, not being classifiable within the theoretical schemes of classical physics.

p Dialectical materialism, like non-dialectical materialism, recognises the objectively real world connection, but its understanding of this connection, and of objective reality, is much deeper and broader than that of metaphysical mechanical materialism. In mechanical materialism objective reality is reduced to absolute, invariable substance, to constant particles that move according to laws established once and for all, and the world connection is correspondingly likened to a direct, necessary connection, representing the whole world after the manner of a gigantic mechanism. Engels called this kind of determinism ’mechanical determinism’. For mechanical determinism the connections existing in nature are reducible in the final analysis to the connections that are studied by classical mechanics, rejecting the objective reality of chance, and recognising necessity, identified with causality, only in its direct, simple, abstract form. Kant and Hume, who are frequently cited by the modern idealists, who consider these philosophers’ theory of causality matchless, developed a mechanistic approach to the world connection, depriving it, however, of its materialist foundation.

p Marxist philosophy has developed a quite different view on the objectively real connection, necessity, regularity, and causality. In accordance with dialectical materialism’s rejection of metaphysical ‘invariabilities’ of all kinds and recognition of only one thing as invariable, viz. the existence of the eternally developing external world, matter, reflected by human consciousness (when the latter exists), Marxist philosophy considers the objectively real world connection as inexhaustible and comprehensive by its actual nature, revealing to cognising man ever new, more meaningful forms and aspects; causality is one of these forms, cognised, like all other forms of connection, more and more completely and precisely with each step of science and practice. Dialectical materialism pays special attention to the reciprocal transitions of cause and effect and to thp 144 relation of causality to other forms of the world connection. Although causality does not exist outside necessity, it is not identical with the latter. It causes chance phenomena that exist objectively as a manifestation and complement of necessity. The problem of causality is related to that of the infinity of matter deep in the depths and infinity of its cognition.

p Quantum mechanics is once more confirming all these statements of dialectical materialism. It owes it to dialectical materialism that it has emerged from the indeterminist impasse into which modern idealism tried to force it; dialectical materialism helped it resolve the philosophical problems before which mechanical materialism came to a halt.

p Heisenberg’s uncertainty relation, Schrodinger’s wave equation, and the novelty of the statistical (probability) laws of quantum mechanics are a new landmark in man’s progressing knowledge of the objectively real, regular, causal connection. The concepts ‘order’, ‘regularity’, and ‘causality’ in physics do not necessarily have to be expressed solely by the quantities and relations of classical mechanics. They can, in particular, be expressed by means of the quantities and relations of quantum mechanics, which reflect moving matter more deeply and accurately; these concepts thereby acquire a new content that classical theory could not know; in other words, quantum mechanics reflects connections that classical mechanics could not embrace. The further penetration of human knowledge into matter is now, undoubtedly, revealing, and will do so in the future, ever deeper and more general connections that do not come into quantum mechanics’ field of applicability, as the developing science of elementary particles witnesses; and the content of the concepts of causality, order, and law in physics will correspondingly undergo a new change.

p The progress of atomic physics led to the spread in modern non-Marxian philosophical literature of an idealist point of view on necessity, law, and causality in nature, viz. to an affirmation that determinism is allegedly bankrupt as regards atomic phenomena, and the principle of causality, if it remained at all, did so only in the sphere of mathematical ideas about the atom. In this case ’physical idealism’, to paraphrase Langevin’s expression, repaid what it had borrowed from philosophical idealism with interest. In this 145 connection let us compare the views of certain modern Western physicists and philosophers on causality with dialectical materialism.

p Heisenberg, for instance, considers the concepts of the objective reality and causality (taken together) as ones that are inherent solely in classical physics. As for quantum mechanics, he thinks that ’the objective’ and ’the real’ are isolated from one another in it; the ‘objective’ is retained only for symbolic representation of the atom by the (mathematical) wave function, and ’the real’ only for describing atomic processes in terms of classical concepts (or in terms of space and time)^^2^^. In accordance with this point of view, determinism or causality (Heisenberg does not distinguish between them)^^3^^, instead of governing events in space and time, operates formally in the mathematical scheme of the atom, events in space and time being governed solely by statistical laws.

p Heisenberg’s ideas about the ‘objectivity’ of the atom are very close to Plato’s philosophy, as their author said more than once.^^4^^ At the same time the following aspect of his outlook is important. According to him, symbolic representation by the wave function (and causality) exclu i des description of atomic processes in terms of classical i (corpuscular) concepts (and statistical laws). They represent complementary aspects in the sense that only their j combination makes it possible to solve problems relating f to atomic theory. But then Heisenberg’s ideas (which are summed up in the complementarity conception formuj lated and developed by Niels Bohr) include a grain of a dia| lectical approach to analysis of atomic processes. We shall return to this point in the sections that follow.

p The positivist philosopher Hans Reichenbach disagreed with Heisenberg; he suggested that, if causality existed, ! then it did so really rather than formally, governing events i in space and time. In his opinion ’a causal supplementation I of observable data by interpolation of unobserved values can be consistently done’.^^8^^ In classical physics, he said, such causal supplementation existed; in quantum mechanics, however, it did not exist, for the reason that the principle of causality allegedly meant the possibility of predicting the future with arbitrary accuracy, but, by the uncertainty principle, ’we cannot expect to be able to make i strict predictions of future observations’.^^8^^ Reichenbach 146 made a step backward compared with Heisenberg, because, from his point of view, the antithesis of statistical and dynamic patterns, which is quite clear in Heisenberg’s reasoning, had been reduced to nought.

p The American physicist P. W. Bridgman holds a similar idealist position, but he is far from the dialectical guesses that abound in the statements of Bohr, Heisenberg, Born, and many other representatives of the Copenhagen interpretation. According to him, the conclusion that causality does not exist in the microworld_j ’is to be accepted without prejudice or passion just as any other experimental result is accepted’.^^7^^ This conclusion, he assumed, corresponded completely to the ’new understanding of the experimental situation’, in the domain of experimental investigation of atomic phenomena, which was expressed in the statement that ’events are not predictable in the realm of small things’.^^8^^

p The American physicist and philosopher Henry Margenau stood for recognition of causality in classical and quantum physics, but for him it was just a connection between ’ constructs’, ’a metaphysical requirement’ presented to scientific ‘constructs’; these‘constructs’were built by the intellect in such a way ’as to generate causal laws’.^^9^^

p Margenau rejected the concept of objective reality that appears in one form or another in the publications of physicists of the Copenhagen school, and also opposed the idea of complementarity or rather the antithesis of its aspects. Bohr, he wrote, condemned himself to ’an eternal dilemma’: either to reject causality for describing nature in terms of classical observables or to describe it only in terms of ’ abstract states, such as ^-function’, the second choice allowing ’causality to be retained’.^^10^^ In Margenau’s opinion, science chose the second path.^^11^^

p Max Born’s statements about causality and determinism are of special interest. He rejected determinism for microphenomena and said that it ’is an idol, not an ideal, in the investigation of nature and, therefore, cannot be used as an objection to the essentially indeterministic, statistical interpretation of quantum mechanics’.^^12^^ At the same time, as if contradicting himself, he supported causality in quantum mechanics. ’The deterministic mechanistic view,’ he wrote, ’produced a philosophy which shut its eyes against the most obvious facts of experience; but a philosophy which rejects not only determinism but causation altogether seems 147 to me just as absurd. I think that there exists a reasonable definition of the cause-effect relation which I have already mentioned: that a certain situation depends on another one.^^13^^

p The following common features are inherent in these statements and in the views on causality of other authors who reject the objectively real connection because of the advances of atomic physics. (1) Causality is isolated from the objectively real external world and becomes a kind of supernatural principle (and the real external world either proves to be a derivative of the mind, spirit, or experience, or is declared to be essentially unknowable); accordingly causality is identified in one way or another with the predictability of what is observed. (2) The difference between mechanical determinism and determinism as understood by dialectical materialism, as a theory of the universal connection of phenomena that discloses new aspects of itself in the infinite process of its cognition, is ignored. (3) Causality is confused with dynamic regularity, being either opposed to statistical regularity or regarded as a statistical average of disordered elementary phenomena. In what follows we shall consider points related to this issue. Here we shall simply outline the trend which should determine our critical analysis of these non-materialist and metaphysical views of causality.

p Isolation of causality from the objectively real world, i.e. rejection of an objectively real causal connection, is an idealist line of argument about the principle of causality. Every law is incomplete, narrow, and does not exhaust the whole of phenomena; the concept of causality reflects the universality of the world connection in only a fragmentary way, but for all that laws and the causal connection exist objectively, independently of the mind cognising them; the all-sidedness of the world connection cannot be exhaustively expressed, once and for all, by a single theoretical scheme of determinism, and it is in this, in particular, that the objective character of the universal connection between phenomena is revealed. It is here that physicists who ignore dialectical materialism sink into idealism.

p Born, for instance, did not agree with mechanical* determinism. He supported indeterminism, understanding this term in the sense of statistical regularity. He, however, either did not want to, or could not, reject regularity, 148 necessity, and Causality in nature and called for a new definition of the relationship of cause and effect. Such a seeming inconsistency of Horn’s as acceptance of indeterminism and retention of causality can be explained by the fact that the spontaneous materialism and its rejection of the ‘traditional’ idealist and metaphysical philosophy, which pushed Born to retention of the objective causal connection, could not solve the problem of the dialectical contradiction associated with problems of the synthesis of particle and wave notions, the combination of dynamic and statistical regularities, etc. These problems can only be solved from the standpoint of dialectical materialism, which Born ignored as the philosophy of modern science.

p Dialectical materialism, as we know, provides a philosophical answer to the problem of causality in quantum mechanics. ’Causality, as usually understood by us, is only a small particle of universal interconnection, but ... a particle not of the subjective but of the objectively real interconnection.’^^14^^ In these words of Lenin’s is said what Born was looking for but did not find.

The problem of determinism in quantum mechanics cannot be solved without a dialectical analysis of necessity and chance, possibility and reality, cause and effect.