The Creed of the Scientist

The attitude of the scientist to a special creed may be a religious or a political creed.

The fundamental difference between the religious and the political creed – that the latter refers to the immediate material reality of the world around us, while the former has as its object another reality beyond the material world – is not important for this special question; it is the problem of creed itself that is to be discussed.

From what has been said one would be inclined to demand that the scientist should never rely on special doctrines, never confine his method of thinking to a special philosophy. He should always be prepared to have the foundations of his knowledge changed by new experience. But this demand would again be an oversimplification of our situation in life for two reasons. The first is that the structure of our thinking is determined in our youth by ideas which we meet at that time or by getting into contact with strong personalities from whom we learn. This structure will form an integrating part of all our later work and it may well make it difficult for us to adapt ourselves to entirely different ideas later on. The second reason is-that we belong to a community or a society. This community is kept together by common ideas, by a common scale of ethical values, or by a common language in which one speaks about the general problems of life.

The common ideas may be supported by the authority of a church, a party or the state and, even if this is not the case; it may be difficult to go away from the common ideas without getting into conflict with the community. Yet the results of scientific thinking may contradict some of the common ideas. Certainly it would be unwise to demand that the scientist should generally not be a loyal member of his community, that he should be deprived of the happiness that may come from belonging to a community, and it would be equally unwise to desire that the common ideas of society which from the scientific point of view are always simplifications should change instantaneously with the progress of scientific knowledge, that they should be as variable as scientific theories must necessarily be.

Therefore, at this point we come back even in our time to the old problem of the twofold truth' that has filled the history of Christian religion throughout the later Middle Ages. There is the very disputable doctrine thatpositive religion — whatever form it may take — is an indispensable need for the mass of the people, while the man of science seeks the real truth back of religion and seeks it only there.“Science is esoteric,’ so it is said, ` it is only for the few.'

If in our time political doctrines and social activities take the part of positive religion in some countries, the problem is still essentially the same. The scientist' s first claim will always be intellectual honesty, while the community will frequently ask of the scientist that — in view of the variability of science — he at least wait a few decades before expressing in public his dissenting opinions.

There is probably no simple solution to this problem, if tolerance alone is not sufficient; but some consolation may come from the fact that it is certainly an old problem belonging to human life.

Coming back now to the counterproposals to the Copenhagen interpretation of quantum theory we have to discuss the second group of proposals, which try to change quantum theory in order to arrive at a different philosophical interpretation. The most careful attempt in this direction has been made by Janossy, who has realized that the rigorous validity of quantum mechanics compels us to depart from the reality concept of classical physics. He therefore seeks to alter quantum mechanics in such a way that, although many of the results remain true, its structure approaches that of classical physics. His point of attack is what is called the reduction of wave packets,' i.e., the fact that the wave function or, more generally, the probability function changes discontinuously when the observer takes cognizance of a result of measurement. Janossy notices that this reduction cannot be deduced from the differential equations of the mathematical formalism and he believes that he can conclude from this that there is an inconsistency in the usual interpretation. It is well known that thereduction of wave packets’ always appears in the Copenhagen interpretation when the transition is completed from the possible to the actual. The probability function, which covered a wide range of possibilities, is suddenly reduced to a much narrower range by the fact that the experiment has led to a definite result, that actually a certain event has happened. In the formalism this reduction requires that the so-called interference of probabilities, which is the most characteristic phenomenon of quantum theory, is destroyed by the partly undefinable and irreversible interactions of the system with the measuring apparatus and the rest of the world. Janossy now tries to alter quantum mechanics by the introduction of so-called damping terms into the equations, in such a way that the interference terms disappear of themselves after a finite time.

Even if this corresponds to reality – and there is no reason to suppose this from the experiments that have been performed – there would still remain a number of alarming consequences of such an interpretation, as Janossy himself points out (e.g., waves which are propagated faster than the velocity of light, interchange of the time sequence of cause and effect, etc.). Therefore, we should hardly be ready to sacrifice the simplicity of quantum theory for this kind of view until we are compelled by experiments to do so.

Among the remaining opponents of what is sometimes called the orthodox' interpretation of quantum theory, Schrodinger has taken an exceptional position inasmuch as he would ascribe the objective reality’ not to the particles but to the waves and is not prepared to interpret the waves as `probability waves only.'

In his paper Are There Quantum Jumps?' he attempts to deny the existence of quantum jumps altogether (one may question the suitability of the term quantum jump’ at this place and could replace it by the less provocative term `discontinuity’).

Schrodinger’s work first of all contains some misunderstanding of the usual interpretation. He overlooks the fact that only the waves in configuration space (or the transformation matrices') are probability waves in the usual interpretation, while the three-dimensional matter waves or radiation waves are not. The latter have just as much and just as little reality’ as the particles; they have no direct connection with probability waves but have a continuous density of energy and momentum, like an electromagnetic field in Maxwell’s theory.

Schrodinger therefore rightly emphasizes that at this point the processes can be conceived of as being more continuous than they usually are. But this interpretation cannot remove the element of discontinuity that is found everywhere in atomic physics; any scintillation screen or Geiger counter demonstrates this element at once. In the usual interpretation of quantum theory it is contained in the transition from the possible to the actual. Schrodinger himself makes no counterproposal as to how he intends to introduce the element of discontinuity, everywhere observable, in a different manner from the usual interpretation.

Finally, the criticism which Einstein, Laue and others have expressed in several papers concentrates on the question whether the Copenhagen interpretation permits a unique, objective description of the physical facts.

Their essential arguments may be stated in the following terms: The mathematical scheme of quantum theory seems to be a perfectly adequate description of the statistics of atomic phenomena. But even if its statements about the probability of atomic events are completely correct, this interpretation does not describe what actually happens independently of or between the observations. But something must happen, this we cannot doubt;

This something need not be described in terms of electrons or waves or light quanta, but unless it is described somehow the task of physics is not completed. It cannot be admitted that it refers to the act of observation only.

The physicist must postulate in his science that he is studying a world which he himself has not made and which would be present, essentially unchanged, if he were not there.

Therefore, the Copenhagen interpretation offers no real understanding of the atomic phenomena.

This criticism demands the old materialistic ontology.

But what can be the answer from the point of view of the Copenhagen interpretation? We can say that physics is a part of science and as such aims at a description and undertanding of nature.

Any kind of understanding, be deduced from the differential equations of the mathematical formalism and he believes that he can conclude from this that there is an inconsistency in the usual interpretation. It is well known that the reduction of wave packets' always appears in the Copenhagen interpretation when the transition is completed from the possible to the actual. The probability function, which covered a wide range of possibilities, is suddenly reduced to a much narrower range by the fact that the experiment has led to a definite result, that actually a certain event has happened. In the formalism this reduction requires that the so-called interference of probabilities, which is the most characteristic phenomenon of quantum theory, is destroyed by the partly undefinable and irreversible interactions of the system with the measuring apparatus and the rest of the world. Janossy now tries to alter quantum mechanics by the introduction of so-called damping terms into the equations, in such a way that the interference terms disappear of themselves after a finite time. Even if this corresponds to reality – and there is no reason to suppose this from the experiments that have been performed – there would still remain a number of alarming consequences of such an interpretation, as Janossy himself points out (e.g., waves which are propagated faster than the velocity of light, interchange of the time sequence of cause and effect, etc.). Therefore, we should hardly be ready to sacrifice the simplicity of quantum theory for this kind of view until we are compelled by experiments to do so. Among the remaining opponents of what is sometimes called the orthodox’ interpretation of quantum theory, Schrodinger has taken an exceptional position inasmuch as he would ascribe the objective reality' not to the particles but to the waves and is not prepared to interpret the waves as probability waves only.’ In his paper entitled Are There Quantum Jumps?' he attempts to deny the existence of quantum jumps altogether (one may question the suitability of the term quantum jump’ at this place and could replace it by the less provocative term discontinuity'). Now, Schrodinger's work first of all contains some misunderstanding of the usual interpretation. He overlooks the fact that only the waves in configuration space (or the transformation matrices’) are probability waves in the usual

A few remarks may be added concerning the formal structure of all the counterproposals hitherto made against the Copenhagen interpretation of quantum theory. All these proposals have found themselves compelled to sacrifice the essential symmetry properties of quantum theory (for instance, the symmetry between waves and particles or between position and velocity).

Therefore, we may well suppose that the Copenhagen interpretation cannot be avoided if these symmetry properties — like the Lorentz invariance in the theory of relativity — are held to be a genuine feature of nature; and every experiment yet performed supports this view.