Ernst Cassirer was a neo-Kantian philosopher who had a great influence on the philosophical implications of quantum physics, by personal contacts with the major quantum physicists, and through his 1936 book Determinism and Indeterminism in Modern Physics. The English translation, published in 1956, was prepared with the help of Henry Margenau, who had studied with Cassirer.
Max Born said it was a satisfaction to him that Cassirer "also sees the philosophical importance of quantum theory not so much in the question of indeterminism but in the possibility of several complementary perspectives in the description of the same phenomena as soon as different standpoints of meaning are taken."
Arthur Stanley Eddington had associated free decisions with "free" electron jumps, a position he repudiated a few years after Cassirer's book.
Cassirer attacked this simplistic notion:
When it is said that the electron is bound in no other way than as demanded by these rules, or that it has a certain playground within which it is "free," this is nothing else and nothing more than a metaphysical mode of expression. From this interpretation of freedom as a mere possibility, bounded by natural laws, there is no path toward that reality of will and decision which concerns ethics. To identify the "selection" (Auswahl) that an electron is able to make from the set of different quantum orbits — in accordance with Bohr's theory — with "choice" (Wahl) in the ethical sense of that concept would be to succumb to a purely linguistic confusion. For a choice exists only when there are not only different possibilities, but where also a conscious differentiation and a conscious decision is made.
Note that Cassirer is here very close to the idea of the two-stage Cogito model of free will, if he would accept the different possibilities as generated by quantum randomness.
But Cassirer strongly defends determinism (p.203), so doubts that quantum mechanics can help with the problem of free will:
The new mode of determination which is to be established is not built on the ruins of nature's conformity to law; rather it joins the latter as a correlative and complement. For this reason alone it is most questionable whether, or in what manner, a relaxation or dissolution of scientific determinism can be made useful for the solution of the fundamental problem of ethics.A "freedom" emanating from such a source and based on such a foundation would be a fatal gift to ethics. For it would contradict the characteristic and positive meaning of ethics; it would not leave room for that moral responsibility the possibility and necessity of which ethics aims to prove. Whenever something is "ascribed" to a person in the ethical sense, it presupposes, and is connected with, some type of prior determination on the part of that person. An action which should simply fall out of the causal nexus, which should take place at random without reasons, would stand entirely alone and could not be referred or ascribed to a persisting ethical subject. Only an action "grounded" in some way can be considered a responsible action, and the value ascribed to it depends on the type, on the quality of these grounds and not on their absence. Thus the question of free will cannot and must not be confused with the question of physical indeterminism. The free will whose establishment concerns ethics is incompatible with a dogmatic fatalism; but it is by no means incompatible with a critically conceived and developed determinism.
Henry Margenau on Ernst CassirerMargenau was a close colleague, perhaps more a disciple, of Ernst Cassirer and generally claimed to agree with Cassirer's thoughts on causality and determinism. When Cassirer died, Margenau was preparing an appendix for the 1956 English translation of Determinism and Indeterminism in Modern Physics. The appendix (and a bibliography) was to bring the question of causality up to date as of 1956. A dozen years later, Margenau was invited to give the Wimmer Lecture at St. Vincent College in Pennsylvania. His topic was Scientific Indeterminism and Human Freedom, and instead of holding to Cassirer's view "that it would be fatal for ethics to tie itself to and, as it were, fling itself into the arms of a limitless indeterminism," Margenau embraced indeterminism as the first step toward a solution of the problem of human freedom. Margenau lamented that "it forces us to part company with many distinguished moral philosophers who see the autonomy of ethics threatened when a relation of any sort is assumed to exist between that august discipline and science." He clearly means his longtime mentor. "Ethics," says Cassirer, "should not be forced to build its nests in the gaps of physical causation, but he fails to tell where else it should build them, if at all."
Ernst Cassirer on Emil du Bois-ReymondCassirer devotes the opening pages of his Determinism and Indeterminism in Modern Physics to the claim that "determinism" in the modern sense of a complete causal physical determinism was not really understood until an essay of du Bois-Reymond in 1872. This seems completely wrong, but Cassirer was very influential for many modern physicists, insisting on subjective versus objective views (mirroring Neils Bohr's dualistic complementarity, with its wave versus particle views. Cassirer preserves a spiritual view, similar to Immanuel Kant's noumenal world view, as the realm of ethics and freedom. Du Bois-Reymond was quite wrong about determinism, which was equated with necessity in the eighteenth-century debates about freedom versus necessity. He is right that those debates turned into questions of freedom versus determinism in the nineteenth century, but they both assumed there were causal chains that threatened human freedom. See chapter 18 on "Cassirer's Thesis" in Ian Hacking's The Taming of Chance for more. Here is Cassirer's somewhat obscure discussion of Laplace's thesis (which is a picture of complete determinism) and du Bois-Reymond's 1872 lecture.
For ScholarsFrom "Concluding Remarks and Implications for Ethics," chapter 13 of Determinism and Indeterminism in Modern Physics
Within the limits of this investigation it is neither possible nor necessary to pursue further the history of the concept of freedom and its systematic significance. The examples quoted are only to prove one thing, that none of the great thinkers who were deeply conscious of the problems connected with this concept and continuously wrestled with them, ever yielded to the temptation to master them simply by denying the general causal principle and equating freedom with causelessness. Such an attempt is not to be found in Plato or Spinoza or Kant. For all of them freedom did not mean indeterminateness but rather a certain form of determinability: determinability through the pure intuition of Ideas, determinability through a universal law of reason that at the same time is the highest law of being, determinability through the pure concept of duty in which autonomy, the will's self-ordering according to law, expresses itself; these are the basic criteria to which the problem of freedom is brought back. That other form of determination, which occurs in the general laws of nature, is here neither denied nor discarded, but rather presupposed. The new mode of determination which is to be established is not built on the ruins of nature's conformity to law; rather it joins the latter as a correlative and complement. For this reason alone it is most questionable whether, or in what manner, a relaxation or dissolution of scientific determinism can be made useful for the solution of the fundamental problem of ethics. A "freedom" emanating from such a source and based on such a foundation would be a fatal gift to ethics. For it would contradict the characteristic and positive meaning of ethics; it would not leave room for that moral responsibility the possibility and necessity of which ethics aims to prove. Whenever something is "ascribed" to a person in the ethical sense, it presupposes, and is connected with, some type of prior determination on the part of that person. An action which should simply fall out of the causal nexus, which should take place at random without reasons, would stand entirely alone and could not be referred or ascribed to a persisting ethical subject. Only an action "grounded" in some way can be considered a responsible action, and the value ascribed to it depends on the type, on the quality of these grounds and not on their absence. Thus the question of free will cannot and must not be confused with the question of physical indeterminism. The free will whose establishment concerns ethics is incompatible with a dogmatic fatalism; but it is by no means incompatible with a critically conceived and developed determinism. We have seen time and again that quantum mechanics has also by no means abandoned the idea of natural order according to law, but has rather lent it a new form. Thus if the idea of ethical freedom is threatened by natural order, it could not expect any help from quantum mechanics. For the problem under consideration, it makes no difference whether we think of natural events as being governed by strict dynamical laws, or whether we merely presuppose a statistical regularity. For from the latter standpoint they would also remain determined to such an extent that the supposed "freedom," a liberum arbitrium indifferentiae, would not find any refuge there. An action which from a physical standpoint is branded as not entirely impossible but in the highest degree improbable is not an action we can count on in any way in the realm of the decisions of our will. Our ethical decisions would be in a sad state if we had to count on such improbabilities and had to make our decisions dependent on them. The extremely improbable is practically the same as the impossible; the degree of predictability which is left us by quantum mechanics would be entirely sufficient to destroy ethical freedom if the latter, in its conception and its essential meaning, were inconsistent with predictability. But one of the essential tasks of philosophical ethics consists of showing why such an opposition does not exist, why freedom does not need to be upheld against physical causality, but instead maintains and asserts itself on its own grounds. "Persistence" is not only a physical but also and at the same time an ethical category, although in an entirely different sense. For all ethical actions must spring from the unity and persistence of a definite ethical character. This in itself shows us that it would be fatal for ethics to tie itself to and, as it were, fling itself into the arms of a limitless indeterminism. From such a standpoint we would have evaluate an action more highly, the more it bears the earmark of the arbitrary, the unforeseen, the unpredictable. Yet true ethical judgment runs in exactly the opposite direction. It does not value behavior highly which is capricious, "uncontrollable," and changing from moment to moment; rather it values a course of action that springs from the basic substratum of the personality and is firmly anchored in it. Ethical character is distinguished by the fact that it is not completely determined from the outside, that in its decisions it is not thrown hither and thither by the changing conditions of the moment but remains itself and persists in itself. By virtue of this persistence we can count on such a person; we rely on his remaining true to himself and on his arriving at his decision not by mood and arbitrariness but by an autonomous law, by that which he himself recognizes and acknowledges right. Schiller sets the foundation of his doctrine of moral freedom on the postulate that there exist ultimately two fundamental theoretical and ethical concepts, before which analysis must come to a halt and acknowledge its limitations. The one is the concept of person, the other the concept of state (Zustand). In man, as finite being, the two determinations must necessarily remain different and cannot be reduced to each other. "The person must be his own ground, for the permanent cannot arise out of change; and thus we have in the first place the idea of the absolute being, grounded in itself — that is, freedom. A state must have a cause; it must follow something, since it does not exist through the person, and it is therefore not absolute; and thus we have in the second place the condition of all dependent being or becoming, viz. time." Accordingly, causality and freedom are as little opposed as are being and time; the structure of our theoretical as well as ethical world depends on the permeation and correct complementation of each by the other. This complementation is of course not to be understood as suggesting that the two factors are simply to be put side by side, or regarded as parts which may be added together and which, by this addition, produce a homogeneous whole. The synthesis here sought and demanded is entirely a synthesis of different elements, which, however, are not incapable of union, though they are qualitatively disparate. This disparity cannot be overcome or eliminated in any way. Thus it becomes clear from this side as well, that a possible change of the physical "causality concept" cannot directly touch ethics. For however physics may change its internal structure, by abandoning, for example, the concept of the simple mass point or the possibility of strict predictions, the opposition in principle between the physical and ethical world, between the realm of nature and the realm of ethics cannot be bridged. These realms will always confront each other in the same manner, no matter to what immanent transformations of their form we consider them subjected. The problem of freedom and nature remains the same, whether we formulate the general laws constituting nature as dynamic or statistical laws. We are concerned here not with a difference in their thing-content, but with a formal difference, or more precisely a difference in category. We cannot do away with the guiding concept of determination in either case, in the structure of the physical word or of the ethical world. But determination follows different categories in the realm of being and in that of duty (Sollen). These categories do not conflict because they belong to entirely different dimensions of consideration. Thus they can never meet in one point; they cannot become identical, nor do they disturb or destroy each other. Equally, they are not distributed over separate special realms of being, but always demand the whole of being, though each from a special "aspect." The methodological problem here before us is by no means restricted to the relation between "nature" and "ethics"; it has a far more general character. It recurs wherever different determinations and interpretations of meaning confront each other. For instance in the case of religion, its philosophical interpretation was again and again faced with the basic problem, whether, and in what manner, the religious explanation of events can be brought into harmony with the other, humanly "natural" one. Again and again at this point the conflict between faith and knowledge sprang up; and for faith the miracle seemed to be "faith's dearest child." An event was more securely understood and established in a religious sense; the more it was documented as a miracle, the more it constituted a breach of the general laws of nature. However, in the modern philosophy of religion since Leibniz and Schleiermacher, this interpretation has undergone a considerable change. It no longer questions the validity of a strict and general order according to law in nature; rather it lends the latter a religious character; it sees in it a proof of the divine nature of being. "A miracle," Schleiermacher maintains, "is nothing but the religious term for an event"; it does not contradict the concept of regularity; rather it elevates this regularity as such into the sphere of religion and expresses it in religious terminology. The aesthetic "sense" is constituted in an analogous manner. Art is not an "imitation of nature," nor does it add something entirely foreign to nature by transforming it according to aesthetic ideals. Rather it discovers the beautiful in nature by measuring it with a new and independent standard. An idol revered in a shrine can be described according to purely scientific principles, and can be represented according to the concepts and categories of science. In this way it becomes a "piece of nature," subject like any other to physicochemical laws. Yet we know that with all these determinations we do not penetrate to its full meaning. The latter is not exhausted by the mere enumeration of scientific data. It demands other criteria, different in principle. No matter from how many viewpoints we may observe and analyze the marble as it natural object, the result will never divulge anything about its form and the beauty of this form, or about its significance in religious worship as an object of religious reverence. And it is just as impossible to arrive at the characteristic content of the problem of freedom if we strictly adhere to the realm of statements of scientific knowledge. This problem also is a problem sui generis, a question which cannot be solved by simple reduction to natural laws but has to be based on an independent type of orderliness according to law, the autonomous orderly structure of the will. If this is kept in mind, it becomes understandable why ethics has nothing to fear and little to hope from the changes in the basic concepts of science which have taken place in modern physics. Now as always it will have to seek and find its own way, a way on which physics can neither confuse nor greatly assist it. Everywhere, as with Spinoza, ethics was bound to a strict naturalism, this situation was not changed in principle. The distinctive methodological character of its approach always broke through at some point or other. Regardless then of how the conflict between determinism and indeterminism will ultimately be decided in the realm of physics, one thing is certain, that the decision of ethics cannot be anticipated by it. For ethics, the cry Hic Rhodus, hic Salta will always be valid at this point.Cf. T. James, Aesop's Fables (New York, 1848), p. 209. Fable 199, "The Boasting Traveller": "A man who had been travelling in foreign parts, on his return home was always bragging and boasting of the great feats he had accomplished in different places. In Rhodes for instance, he said he had taken such an extraordinary leap, that no man could come near him, and he had witnesses there to prove it. 'Possibly,' said one of his hearers, 'but if this be true, just suppose this to be Rhodes, and then try the leap again."'Ethics must pass judgment in its own right on the problem of freedom. It cannot refer the problem to another court, nor can it acknowledge any prejudice in this its most proper basic question. The student of ethics who inquires after the possibility of freedom cannot expect any essential help from physics, as long as he poses his question in the only sense significant for ethics. Even if a solution to the riddle could be offered in the form of some physical indeterminism, he would have to reject it with the words Queen Christina of Sweden is said to have used when she renounced crown and kingdom: non mi bisogna e non mi basta.Cf. Leibniz, "Theodicee": "As a comment on the explanations of such mysteries which appear from time to time, one might cite what the queen of Sweden had inscribed on a medal, with reference to the crown she had abandoned: 'I don't need it, and it's not enough anyway.' " Philosophische Schriften, ed. Gerhardt, 6, 81.This state of affairs becomes the more apparent, the more we examine the individual problems to which the indeterminism of quantum theory has led us. The question may be raised as to what constituted the new understanding and the new fundamental view which atomic physics put in the place of the classical physical concepts. It consisted primarily of no longer posing the question why? in the same manner and at the same point as before. In Bohr's theory the path of an electron is determined by two different conditions, one classical, the other required by quantum theory. From the interaction of these conditions it develops that the electron can move only in certain designated circles whose radii are in proportion to the squares and whose frequencies are in proportion to the cubes of the quantum numbers; further it was shown that the electron can be raised from an inner to an outer orbit upon absorption of energy, and that it can fall from an outer to an inner orbit by energy emission. But to the question as to the why? of these two processes the theory lacks an answer. It merely determines that the process occurs and how it occurs; it narrows down the process, observed and accepted as empirically given, to certain precisely formulable rules. When it is said that the electron is bound in no other way than as demanded by these rules, or that it has a certain playground within which it is "free," this is nothing else and nothing more than a metaphysical mode of expression. From this interpretation of freedom as a mere possibility, bounded by natural laws, there is no path toward that reality of will and decision which concerns ethics. To identify the "selection" (Auswahl) that an electron is able to make from the set of different quantum orbits — in accordance with Bohr's theory — with "choice" (Wahl) in the ethical sense of that concept would be to succumb to a purely linguistic confusion. For a choice exists only when there are not only different possibilities, but where also a conscious differentiation and a conscious decision is made. To credit the electron with such acts would constitute a severe relapse into anthropomorphism, of which modern physics, insisting more strongly than ever on emancipation from the anthropomorphic elements in the description of nature, cannot and has not become guilty. For modern physics the electron has become so unlike a personal unity that it demands exactly the opposite step from us; the physicist ceases even to consider and treat the electron as an individual in the ordinary sense of the word — that is, as a single thing. Far from favoring any form of personification, modern physics even questions the attempt at mere identification, at retention of even numerical identity of individual electrons. We have seen how the theoretical establishment of quantum statistics in its various forms was led again and again to question a fully determined individuality of electrons. We can no longer isolate two electrons from an electronic grouping and juxtapose them as independent individual entities in the way that used to be considered possible for two material points within the system of classical physics. If we take two electrons which are at first located at two distant points A and B, and which then collide, after which the positions A and B are again occupied each by one electron, then, according to the general considerations and principles of quantum theory it is meaningless to ask whether the same electrons again occupy points A and B or whether they exchanged positions. Such a form of identification not only cannot be attained, but according to the principles of quantum theory cannot even be sought after, and this has been realized and emphasized with ever increasing clarity. A "re-recognition" of an electron is no longer possible in the same manner and with means analogous to those which were possible within the framework of classical physics. Thus here, where physical individuality itself becomes questionable, we are further than ever removed from ethical individuality, from the "person" as the subject of autonomous decisions of the will; the distance between the two is not diminished but rather more strongly accentuated. We find ourselves forced to the same conclusion when we approach the question from the opposite direction, by fixing our attention solely on ethical problems as such. Is it really true that what these problems demand of us stands in apparent or actual opposition to a certain form of natural causality? Does not this question extend, when asked with true accuracy and consistency, to the whole of this natural causality? Fundamentally only one decision remains to be made: the possibility of uniting "nature" and "freedom" must be either asserted or denied. One is invariably led to a denial, to an insoluble antinomy, when one understands "determinism" in its metaphysical instead of its critical sense. For the moment one does this, causality ceases to be a principle of physical knowledge; it is hypostatized as an independent being, and becomes a metaphysical fate (Fatum) with which the human will conflicts and to which it must ultimately acknowledge itself captive. This uncritical metamorphosis of causality into a thinglike necessity or imperative (Mussen), a kind of kismet, can be countered only by a change of principle, by a philosophical about-face. It is not sufficient when, in order to avoid or weaken the consequences, one merely attempts a "loosening" which is unable to change the nature of the bond here presupposed. When once the rules of knowledge are changed into a thinglike compulsion, or the norm of causal understanding into a necessity which inexorably forces its form on events, and thus, as it were, puts them in fetters, all subsequent rectification of this fundamental methodological error comes too late. It does not matter in this case of the causality governing nature in the form of strict dynamic laws, or of mere statistical laws. The real fault lies in a different place and must be corrected by methods which are different in principle. If this kind of necessity is once included in the formulation of natural laws, it will make itself no less strongly and imperatively felt when we consider statistical regularities as the basic feature of natural events than when we think of the latter as being governed by strictly deterministic relations in the sense of classical physics. Neither the one nor the other path leaves an opening for that sphere of freedom which ethics claims for itself. To make this clear it is sufficient to cast a glance at the historical development of the problem. The first contact between the problems of moral philosophy and those of statistics was brought about by the so-called "moral statistics." This discipline, in the formulation given to it by its founder, Quetelet, consciously set itself the task of abolishing the frontiers between merely physical and purely moral phenomena, by undertaking to show that both groups of phenomena are subject to exactly the same regularity, and can be described fully and without exception by means of the latter. According to Quetelet there exists a physics of human society in exactly the same sense as there is a physics of atoms and of the material bodies made from them. The apparent contradiction in the "what," in the mere substratum of happening, is more than bridged. It is completely abolished by the insight that happenings in both cases are subject to exactly the same regularities. These regularities are of the same character and strictness, whether they concern material or spiritual, physical or ethical phenomena. In this way ethics was in principle included in the circle of calculability, which hitherto seemed reserved to physics. And the only methodologically compelling consequence resulting from this postulate had to be that freedom was lost for both ethics and physics. The numerical laws of statistics seemed to show, in an immediately comprehensible and compelling manner, that in the realm of phenomena of the will also there is no room for any free choice. The law of large numbers obliterates the differences which we are in the habit of making between appearances of nature and appearances of the will, and within the latter, between free and unfree actions. From the standpoint of knowledge, from the standpoint of the historian and the sociologist, these differences must disappear. They only see the never changing chain of causes and effects, through which each individual event and entity is held together with every other in such a manner that it loses its particular meaning, its significance as an individual. Even the ethical values by which we seek to elevate certain groups of actions and to secure them a privileged position are lowered to purely accidental determinations, when viewed from this standpoint. The statistical rule embraces both the good and the bad, and tolerates neither an essential difference of being nor a methodological difference of explanation between them. "Crimes are recurring each year in equal numbers with the same punishments, and in the same proportions," says Quetelet, and he seeks to show that this principle refers not only to the type of crime but also to all their apparently accidental external circumstances. Not only will there be, in a given country, a definite number of murders committed annually, but the methods and weapons used will show it relation just as uniform as that which we are able to observe in physical phenomena, such as for instance in the movements of the tides. From this basic view there developed that form of materialistic philosophy of history which sees in the strictly mechanical determination which has to be acknowledged and used for both natural and historical considerations the connecting and conciliatory link between the two. Statistics everywhere took on the role of the true spiritual mediator. Thus Buckle in the introduction to his History of Civilization in England (1857), where he pursues Quetelet's basic idea further, writes that those who have a steady conception of the regularity of events and have firmly seized the great truth that the actions of men, being guided by preceding causes, are always consistent will no longer be astonished by the fact that this regularity extends to include even the smallest and apparently most insignificant. "Indeed, the progress of inquiry is becoming so rapid and earnest, that I entertain little doubt that before another century has elapsed, the chain of evidence will be complete, and it will be as rare to find an historian who denies the undeviating regularity of the moral world, as it now is to find a philosopher who denies the regularity of the material world. . . . The . . . proofs of our actions being regulated by law, have been derived from statistics; a branch of knowledge which, though still in its infancy, has already thrown more light on the study of human nature than all the sciences put together." All this demonstrates why the statistical character of the laws of quantum mechanics cannot in itself decide the question of ethical freedom, without the help of quite different considerations. From the same premises offered by physics, entirely dissimilar conclusions can be drawn, according to the rules of the philosophical and epistemological method accepted as valid. From the statistically "given," a path can be followed equally well in the direction of an indeterministic view as in the direction of a strict determinism and mechanism. For even statistical thought, as its history clearly shows, is by no means immune from the danger that its results will at a certain point "turn rigid" dogmatically, that the law of knowledge which is established in it undergoes such an interpretation that it appears to the thinking mind as an external, absolute, and compelling entity. As soon as this stage is reached, we find ourselves again caught in the antinomy of the problem of freedom; and this can be countered, as with dynamical laws, only by a radical transformation of the question, by a kind of Copernican revolution. Thus Simnel writes in his epistemological analysis of the concept of historical laws (G. Simmel, Die Probleme der Geschichtsphilosophie (2d ed. Leipzig, 1905) pp. 104 ff.):"If it is considered a social law that among 10,000 deaths per year there are a definite number of suicides, there has been a misunderstanding. For each one of the suicides under consideration is merely the result of social and psychological forces, or rather of the laws governing these; and the fact that there is a total of so and so many suicides is the result of the action of these laws on a given material, and thus cannot itself be a law. . . . The summation of these cases is a synthesis undertaken by the observer; the fact that it yields this particular result has of course an objective foundation, yet only through the circumstance that each of its elements has one, whereas it would be a faulty circle and a kind of mystical teleology to attempt to deduce from the necessary determination of the result the conclusion that the elements are determined. . . . The history of each individual suicide furnishes the material for this . . . question, but does not answer it, because the question applies not to the level of immediate realities but to those levels in which the more abstract categories are developed from these realities. In the same way, for instance, the geometrical description of crystalline forms and of their systematic arrangement is not concerned, according to this standpoint, with the energies which cause each individual crystal to form."If one adheres to this fundamental interpretation, he will find that the προτων ψευδος, the original fallacy, of the entire causal problem consists of considering laws themselves as a kind of reality and in describing them by predicates which are only applicable to realities. Once this confusion has arisen, there is no way out of the labyrinth. It is useless to attempt to save freedom by putting statistical regularities in place of dynamic laws, for the stumbling block in the way of recognizing and making visible the problems of ethics is not the type of law accepted; rather it is the ambiguous and epistemologically insufficient formulation of the concept of law as such. But in another indirect sense the problems of quantum mechanics can be used to draw a conclusion of general philosophical significance. What modern physics has taught us is the fact that the change of standpoint which we have to make whenever we move from one dimension of meaning to another, whenever we exchange the world of science for that or ethics, art, etc. is not confined to this type of transition alone. The manifold of perspectives which open up before us has its counterpart within the scientific realm itself. Modern physics had to abandon the hope of exhaustively presenting the whole of natural happening by means of a single strictly determined system of symbols. It finds itself faced with the necessity of applying various types of symbols, of schematic explanations to the same event. It has to describe one and the same entity as a particle and as a wave, and must not be deterred in this use by the fact that the intuitive combination of the two pictures proves impossible. When the fundamental task of physical knowledge, the connection of phenomena into firm orders according to law, demands a duality of description, the habits and demands of intuitive representation and understanding must be subordinated to this fundamental requirement. When, even in science, such a superposition of dissimilar aspects is necessary, it will be the more easily understandable that we shall meet such a superposition again as soon as we go outside its realm - as soon as we seek to realize the full concept of reality, which requires the cooperation of all functions of the spirit and can only be reached through all of them together.