Physics and Philosophy

Werner Heisenberg


Heisenberg, Werner. Physics and Philosophy: The Revolution in Modern Science. 1958. London, EN: Penguin Books, 2000. Paperback: 9780141182155.


“Nobel Prize winner Werner Heisenberg's classic account explains the central ideas of the quantum revolution, and his celebrated Uncertainty Principle. The theme of Heisenberg's exposition is that words and concepts familiar in daily life can lose their meaning in the world of relativity and quantum physics. This in turn has profound philosophical implications for the nature of reality and for our total world view.”


Introduction by Paul Davies, 1989

“True revolutions in science … change the concepts on which the subject is based” (vii)

“two dramatically new theories”—“relativity” and “quantum mechanics” (vii)

“a model of clarity and one of the most lucid accounts of the so-called Copenhagen interpretation of quantum mechanics” (viii)

“space-time is as much a part of the physical universe as matter” (viii)

“As Heisenberg remarks, the idea that time does not stretch back for all eternity but was created with the universe was anticipated in the fifth century by St Augustine. There is thus a scientific counterpart to the creation ex nihilo of Christian tradition” (ix)

“quantum mechanics is a statistical theory” (x)

“the chance element is inherent in the nature of the quantum system and not merely imposed by our limited grasp of all the variables that affect the system” (x)

“the microworld of atoms and particles is considered to differ in scale, but not in ontological status, from the macroworld of experience” (xii)

“In a classical world our observations do not create reality: they uncover it” (xii)

“an electron or an atom cannot be regarded as a little thing in the same sense that a billiard ball is a thing” (xii)

“it is the observations alone that create the reality of the electron” (xii)

“an abstract encodement of a set of potentialities or possible outcomes of measurements” (xii)

“complementarity … that the same system can display apparently contradictory properties” (xiii)

“Any talk of what is ‘really’ going on is just an attempt to infuse the quantum world with a spurious concreteness for ease of imagination” (xiv)

“Physicists would like to derive the classical world as some sort of macroscopic limit of the quantum world, not assume it a priori” (xv)

“If the entire universe is the quantum system of interest, there clearly does not exist a wider macroscopic environment, or external measuring apparatus, into which quantum fuzziness can fade away” (xvi)

“This means serenely accepting the full range of quantum alternatives as actually existing realities” (xvi)

Chapter 1: An Old and a New Tradition

Of atomic weapons: “every tool carries with it the spirit by which it has been created” (1)

Of modern science: “its complete internationality” (2)

“In this exchange of thoughts the one side, the old tradition, will be different in the different parts of the world, but the other side will be the same everywhere and therefore the results of this exchange will be spread over all areas in which the discussions take place” (2)

“the change in the concept of reality manifesting itself in quantum theory is not simply a continuation of the past; it seems to be a real break in the structure of modern science” (2)

Chapter 2: The History of Quantum Theory

“the application of the known laws did not lead to sensible results” (3)

“The idea that energy could be emitted or absorbed only in discrete energy quanta was so new that it could not be fitted into the traditional framework of physics” (4)

“Light could either be interpreted as consisting of electromagnetic waves, according to Maxwell’s theory, or as consisting of light quanta” (5)

Bohr in 1913: “If the atom can change its energy only by discrete energy quanta, this must mean that the atom can exist only in discrete stationary states, the lowest of which is the normal state of the atom. Therefore, after any kind of interaction the atom will finally always fall back into its normal state” (6)

“How could it be that the same radiation that produces interference patterns, and therefore must consist of waves, also produces the photoelectric effect, and therefore must consist of moving particles?” (7)

“the attempt to describe atomic events in the traditional terms of physics led to contradictions” (7)

“ideal experiments … were designed to answer a very critical question irrespective of whether or not they could actually be carried out” (7)

“in 1924 de Broglie in France tried to extend the dualism between wave description and particle description to the elementary particles of matter, primarily to the electrons” (8)

“quantum theory finally emerged from two different developments” (9):

1) “from Bohr’s principle of correspondence” (9)

  • “one should write down the mechanical laws not as equations for the positions and velocities of the electrons but as equations for the frequencies and amplitudes” (10)

  • “The equations of motion in Newtonian mechanics were replaced by similar equations between matrices” (10)

  • “the matrices representing position and momentum of the electron do not commute” (10)

2) “The other development followed de Broglie’s idea of matter waves” (10):

“Thus one finally had a consistent mathematical formalism, which could be defined in two equivalent ways starting either from relations between matrices or from wave equations” (10)

“The electromagnetic waves were interpreted not as ‘real’ waves but as probability waves” (11)

“one essential feature … the probability wave was something entirely new in theoretical physics since Newton” (11)

“Probability in mathematics or in statistical mechanics means a statement about our degree of knowledge of the actual situation” (11)

“The probability wave of Bohr, Kramers, Slater, however, meant more than that; it meant a tendency for something” (11)

“It was a quantitative version of the old concept of ‘potentia’ in Aristotelian philosophy. It introduced something standing in the middle between the idea of an event and the actual event, a strange kind of physical reality just in the middle between possibility and reality” (11)

“autumn of 1926 in Copenhagen” (12)

“led to a complete … satisfactory clarification of the situation” (12)

“Can nature possibly be as absurd as it seemed to us in these atomic experiments?” (12)

“Schrödinger had described the atom as system not of a nucleus and electrons but of a nucleus and matter waves” (13)

“Bohr considered the two pictures—particle picture and wave picture—as two complementary descriptions of the same reality” (13)

“since the spring of 1927 one has had a consistent intepretation of quantum theory, which is frequently called the ‘Copenhagen interpretation’” (13)

Chapter 3: The Copenhagen Interpretation of Quantum Theory

“The Copenhagen interpretation of quantum theory starts from a paradox” (14)

“A probability function is written down which represents the experimental situation at the time of measurement, including even the possible errors of the measurement” (15)

“This probability function represents a mixture of two things, partly a fact and partly our knowledge of a fact” (15)

“the probability function does not in itself represent a course of events in the course of time. It represents a tendency for events and our knowledge of events” (15)

“whether it refers to epistemology or to ontology” (17)

“complementary” — “The two pictures are of course mutually exclusive, because a certain thing cannot at the same time be a particle (i.e., substance confined to a very small volume) and a wave (i.e., a field spread out over a large space)” (18)

“But what happens ‘really’ in an atomic event?” (19)

“we cannot completely objectify the result of an observation, we cannot describe what ‘happens’ between this observation and the next” (19)

“This looks as if we had introduced an element of subjectivism into the theory” (19)

“the term ‘happens’ is restricted to the observation” (20)

“in natural science we are not interested in the universe as a whole, including ourselves, but we direct our attention to some part of the universe and make that the object of our studies” (20)

“possibilities or better tendencies … are completely objective, they do not depend on any observer” (21)

“our knowledge of the system” is “subjective” (21)

“our object has to be in contact with the other part of the world, namely, the experimental arrangement, the measuring rod, etc., before or at least at the moment of observation” (21)

“The probability function does … not describe a certain event but, at least during the process of observation, a whole ensemble of possible events” (22)

“the transition from the ‘possible’ to the ‘actual’ takes place during the act of observation” (22)

“It applies to the physical, not the psychical act of observation, and we may say that the transition from the ‘possible’ to the ‘actual’ takes place as soon as the interaction of the object with the measuring device, and thereby with the rest of the world, has come into play; it is not connected with the act of registration of the result by the mind of the observer” (22)

“In classical physics science started from the belief … that we could describe the world or at least parts of the world without any reference to ourselves” (22)

“There is no use in discussing what could be done if we were other beings than we are” (23)

“At this point we have to realize, as von Weizsäcker has put it, that ‘Nature is earlier than man, but man is earlier than natural science’” (23)

Commentator’s Note: This statement is the key to the whole thing. To Heisenberg’s book, to quantum mechanics, to the project of the reading club that has arrived at this historical text. Nature > humanity > science. This nature is Meillassoux’s nature; this humanity is Latour’s humanity. We cannot conduct the work of natural science, or of empirical work more broadly, without this double situation: science against the backdrop of the human; the human against the backdrop of nature.

“If the measuring device would be isolated from the rest of the world, it would be neither a measuring device nor could it be descsribed in the terms of classical physics at all” (24)

“Our scientific work in physics consists in asking questions about nature in the language that we possess and trying to get an answer from experiment by the means that are at our disposal” (25)

“It is understandable that in our scientific relation to nature our own activity becomes very important when we have to deal with parts of nature into which we can penetrate only by using the most elaborate tools” (25)

Chapter 4: Quantum Theory and the Roots of Atomic Science

“one may say that atomic physics has turned science away from the materialistic trend it had during the nineteenth century” (26)

“The idea of the smallest, indivisible ultimate building blocks of matter first came up in connection with the elaboration of the concepts of Matter, Being and Becoming” (26)

“three fundamental ideas of philosophy” (26)

  • “the material cause of all things” (26)
  • “answered in conformity with reason” (26)
  • “must be possible to reduce everything to one principle” (26)

“Looking back to the development of Greek philosophy up to this point one realizes that it has been borne from the beginning to this stage by the tension between the One and the Many” (28-29)

“when one carried the idea of fundamental unity to the extreme one came to that infinite and eternal undifferentiated Being which, whether material or not, cannot in itself explain the infinite variety of things” (29)

“the solution of Heraclitus, that the change itself is the fundamental principle” (29)

“modern physics is in some way extremely near to the doctrines of Heraclitus. If we replace the word ‘fire’ by the word ‘energy’ we can almost repeat his statements word for word from our modern point of view” (29)

Empedocles > “pluralism” (30)

Atomists > “Being is not only One, it can be repeated an infinite number of times. This is the atom, the indivisible smallest unit of matter” (31)

“the Void … not nothing; it was the carrier for geometry and kinematics, making possible the various arrangements and movements of atoms” (31)

“causality can only explain later events by earlier events, but it can never explain the beginning” (32)

“The smallest parts of matter are not the fundamental Beings, as in the philosophy of Democritus, but are mathematical forms. Here it is quite evident that the form is more important than the substance of which it is the form” (34)

“Historically the word ‘atom’ … was referred to the wrong object” (34)

“These smaller units are nowadays called elementary particles” (34)

“What is an elementary particle?” (34)

“It is a possibility for being or a tendency for being” (35)

“Since mass and energy are, according to the theory of relativity, essentially the same concepts, we may say that all elementary particles consist of energy. This could be interpreted as defining energy as the primary substance of the world” (35)

“The elementary particles are certainly not eternal and indestructible units of matter, they can actually be transformed into each other” (35)

“the elementary particles will finally also be mathematical forms, but of a much more complicated nature” (36)

“the mathematical forms that represent the elementary particles will be solutions of some eternal law of motion for matter” (36)

“the transmutation of energy into matter makes it possible that the fragments of elementary particles are again the same elementary particles” (37)

“This possibility of checking the correctness of a statement experimentally with very high precision and in any number of details gives an enormous weight to the statement that could be attached to the statements of early Greek philosophy” (38)

Commentator’s Note: look and see for yourself. Basic principle of generic science.

Chapter 5: The Development of Philosophical Ideas Since Descartes in Comparison with the New Situation in Quantum Theory

“the strongest impulse had come from the immediate reality of the world in which we live and which we perceive by our senses” (39)

Commentator’s Note: generic science.

“in the philosophy of Plato one already sees that another reality begins to become stronger” (39)

“immediate connection with truth … with God is the new reality that has begun to become stronger than the reality of the world as perceived by our senses” (39)

“The great development of natural science since the sixteenth and seventeenth centuries was preceded and accompanied by a development of philosophical ideas which were closely connected with the fundamental concepts of science” (40)

“Descartes … it is simply impossible that God should have deceived me” (40)

“his starting point with the ‘triangle’ God-World-I simplifies in a dangerous way the basis for further reasoning” (40)

“Greek philosophy” > “fundamental unifying principle”; “Descartes” > “fundamental division” (41)

“the combination of empirical knowledge with mathematics … the possibility of arriving in this way at some knowledge that could be kept apart completely from the theological disputes raised by the Reformation” (42)

“in their discussions the name of God or a fundamental cause should not be mentioned” (42)

“one can describe the world without speaking about God or ourselves” (42)

“Natural science … describes nature as exposed to our method of questioning” (43)

“Cartesian partition … metaphysical realism. The world, i.e., the extended things, ‘exist’” (43)

“distinguished from practical realism … its content does not depend on the conditions under which it can be verified” (43)

“there are statements that can be objectivated” (43)

“Dogmatic realism claims that there are no statements concerning the material world that cannot be objectivated” (43)

“Dogmatic realism” is “not a necessary condition for natural science” (43)

The scientist’s “statements are not meant to depend upon the conditions under which they can be verified” (44)

“Metaphysical realism goes one step further than dogmatic realism by saying that ‘the things really exist’” (44)

“Our perceptions are not primarily bundles of colors or sounds; what we perceive is already perceived as something” (45)

Commentator’s Note: This is also Heidegger’s claim, and Michael Polanyi’s.

“The philosophic thesis that all knowledge is ultimately founded in experience has in the end led to a postulate concerning the logical clarification of any statement about nature” (46)

“regarding their position in Newtonian mechanics they were well defined, but in their relation to nature they were note” (46)

“No physicist would be willing to follow Kant here, if the term ‘a priori’ is used in the absolute sense that was given to it by Kant” (48)

“doctrines of Kant” (48)

“The theory of relativity has changed our views on space and time” (48)

“The law of causality is no longer applied in quantum theory” (49)

“the law of conservation of matter is no longer true for the elementary particles” (49)

But Kant “was convinced that his concepts would be ‘the basis of any future metaphysics that can be called science’ (49)”

“The a priori concepts which Kant considered an undisputable truth are no longer contained in the scientific system of modern physics” (50)

“What Kant had not foreseen was that these a priori concepts can be the conditions for science and at the same time can have only a limited range of applicability” (50)

“Modern physics has changed Kant’s statement about the possibility of synthetic judgements a priori from a metaphysical one into a practical one” (50)

“The ‘thing-in-itself’ is for the atomic physicist … a mathematical structure … indirectly deduced from experience” (51)

“Modern physics … as model to check the results of some important philosophic systems of the past” (51)

Commentator’s Note: This is what makes Parmenides’ claims interesting. They are testable and ultimately falsifiable.

“Any concepts or words which have been formed in the past through the interplay between the world and ourselves are not really sharply defined with respect to their meaning; that is to say, we do not know exactly how far they will help us in finding our way in the world” (51)

“it will never be possible by pure reason to arrive at some absolute truth” (51)

“concepts may, however, be sharply defined with regard to their connections” (52)

“This is actually the fact when the concepts become a part of a system of axioms and definitions which can be expressed consistently by a mathematical scheme” (52)

“some concepts form an integral part of scientific methods, since they represent for the time being the final result of the development of human thought in the past” (52)

“practically a priori” (52)

Chapter 6: The Relation of Quantum Theory to Other Parts of Natural Science

“The mathematical image of the system ensures that contradictions cannot occur in the system” (53)

“Newtonian mechanics cannot be improved; it can only be replaced by something essentially different!” (56)

“electromagnetic phenomena cannot adequately be described by the concepts of Newtonian mechanics” (56)

“a new closed system of definitions and axioms and of concepts that can be represented by mathematical symbols, which is coherent in the same sense as the system of Newton’s mechanics, but is essentially different from it” (56)

“new phenomena that had been observed could only be understood by new concepts which were adapted to the new phenomena in the same way as Newton’s concepts were to the mechanical events” (56)

“four systems”

  1. “Newtonian mechanics”: “all mechanical systems,” “fluids,” “elastic vibration,” “acoustics,” “statics,” “aerodynamics” (57)
  2. “in connection with the theory of heat”: “probability,” “entropy” (57)
  3. “the phenomena of electricity and magnetism”: “electrodynamics, special relativity, optics, magnetism … the de Broglie theory of matter waves” (58)
  4. “quantum theory”: “the probability function”—“quantum and wave mechanics, the theory of atomic spectra, chemistry, and the theory of other properties of matter like electric conductivity, ferromagnetism, etc.” (58)

“The first set is contained in the third as the limiting case where the velocity of light can be considered as infinitely big” (58)

The first set “is contained in the fourth as the limiting case where Planck’s constant of action can be considered as infinitely small” (58)

“The first and partly the third set belong to the fourth as a priori for the description of the experiments” (58)

“The second set can be connected with any of the other three sets without difficulty and is especially important in its connection with the fourth” (58)

“The independent existence of the third and fourth sets suggests the existence of a fifth set, of which one, three, and four are limiting cases” (59)

Commentator’s Note: I belive this fifth set is quantum electrodynamics. As per Wikipedia, “Shin’ichirō Tomonaga, Julian Schwinger and Richard Feynman were jointly awarded with the 1965 Nobel Prize in Physics for their work in this area,” and this book dates from 1958. Likewise, Heisenberg “was awarded the 1932 Nobel Prize in Physics ‘for the creation of quantum mechanics.’”

“The limitations of the field can generally not be derived from the concepts. The concepts are not sharply defined in their relation to nature … limitations will therefore be found from experience, from the fact that the concepts do not allow a complete description of the observed phenomena” (59)

“something has to be added to the laws of physics and chemistry before the biological phenomena can be completely understood” (60)

“the two processes, that of science and that of art, are not very different. Both science and art form in the course of the centuries a human language by which we can speak about the more remote parts of reality” (66)

Commentator’s Note: And as Badiou would argue, both science and art are truth procedures that elaborate those remote parts of reality by way of the forcing mechanisms, i.e., the expansion of the set of terms that defines the situation.

Chapter 7: The Theory of Relativity

“Einstein in 1905 … established the ‘apparent’ time of the Lorentz transformation as the ‘real’ time and abolished what had been called ‘real’ time by Lorentz” (70)

“the common words ‘space’ and ‘time’ refer to a structure of space and time that is actually an idealization and oversimplification of the real structure” (70)

“future and past are separated by a finite time interval the length of which depends on the distance from the observer” (71)

“one could consider mass and energy as two different forms of the same ‘substance’” (74)

“general relativity … is more hypothetical than the first one [special relativity]” (76)

“There is as yet no experimental evidence for this red shift” (77)

Commentator’s Note: It took until 2011 for Einstein’s prediction to be confirmed.

“is space finite or infinite? What was there before the beginning of time? What will happen at the end of time? Or is there no beginning and no end?” (78)

Commentator’s Note: Parmenidean meditations.

“the precise and consistent formulation of these concepts in the mathematical language of Newton’s mechanics or their careful analysis in the philosophy of Kant had offered no protection against the critical analysis possible through extremely accurate measurements” (81)

“the success of the theory of relativity warned the physicists against the uncritical use of concepts taken from daily life or from classical physics” (81)

Chapter 8: Criticism and Counterproposals to the Copenhagen Interpretation of Quantum Theory

“The first … tries to change the philosophy without changing the physics” (82)

“The second … to change quantum theory” (82)

“The third … without making definite counterproposals” (82-83)

“the introduction of the observer must not be misunderstood to imply that some kind of subjective features are to be brought into the description of nature. The observer has, rather, only the function of registering decisions, i.e., processes in space and time, and it does not matter whether the observer is an apparatus or a human being; but the registration, i.e., the transition from the ‘possible’ to the ‘actual,’ is absolutely necessary here and cannot be omitted from the interpretation of quantum theory” (89)

“we see from these formulations how difficult it is when we try to push new ideas into an old system of concepts belonging to an earlier philosophy … when we attempt to put new wine into old bottles” (81)

“the scientist should never rely on special doctrines [religious or political], 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” (91)

“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” (91)

Commentator’s Note: Again, this is Heraclitus’ common, necessary for the process of generic science.

“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” (92)

“the actual” as “the foundation of any physical interpretation” (95)

“any knowledge of the ‘actual’ is … by its very nature an incomplete knowledge” (95)

Chapter 9: Quantum Theory and the Structure of Matter

“early Greek philosophy”: “the concept of cosmic matter, a world substance” (97)

Aristotle: “relation between form and matter” (97)

Descartes: “matter was primarily thought of as opposed to mind” (98)

19th century natural science: “dualism between matter and force” (98)

Next: “independent of its chemical properties matter could be measured by its mass” (99)

But “the concept of the chemical element had not yet reached the point where one could understand the unity of matter” (100)

“The nucleus” has a radius “about a hundred thousand times smaller than that of the atom” but “contains almost its entire mass” (100)

“At the present time about twenty-five different new elementary particles are known” (107)

Commentator’s Note: There are now 57 known elementary particles.

“the experiments have shown the complete mutability of matter” (107)

“All the elementary particles are made of the same substance, which we may call energy or universal matter; they are just different forms in which matter can appear” (107)

“we can say that the matter of Aristotle, which is mere ‘potentia,’ should be compared to our concept of energy, which gets into ‘actuality’ by means of the form, when the elementary particle is created” (107)

“The theory of relativity is connected with a universal constant in nature, the velocity of light. This constant determines the relation between space and time and is therefore implicitly contained in any natural law which must fulfill the requirements of Lorentz invariance” (110)

“Quantum theory is connected with another universal constant of nature, Planck’s quantum of action. An objective description for events in space and time is possible only when we have to deal with objects or processes on a comparatively large scale, where Planck’s constant can be regarded as infinitely small” (111)

“One needs at least three fundamental units for a complete set of units” (111)

“A unit of length, one of time, and one of mass is sufficient to form a complete set. One could replace them by units of length, velocity and mass; or by units of length, velocity and energy, etc. But at least three fundamental units are necessary. Now, the velocity of light and Planck’s constant of action provide only two of these units. There must be a third one, and only a theory which contains this third unit can possibly determine the masses and other properties of the elementary particles” (111)

Commentator’s Note: There are currently 19 fundamental physical constants. These are the gravitational constant G, the speed of light c, the Planck constant h, the 9 Yukawa couplings for the quarks and leptons (equivalent to specifying the rest mass of these elementary particles), 2 parameters of the Higgs field potential, 4 parameters for the quark mixing matrix, 3 coupling constants for the gauge groups SU(3) × SU(2) × U(1) (or equivalently, two coupling constants and the Weinberg angle), and a phase for the QCD vacuum.

Chapter 10: Language and Reality in Modern Physics

“scientific problems have finally become connected with political issues” (113)

“one has not yet found the correct language with which to speak about the new situation and that the incorrect statements published here and there in the enthusiasm about the new discoveries have caused all kinds of misunderstanding” (113)

“ordinary language was based upon the old concepts of space and time” (119)

“Euclidean geometry is just made correct by our own measures” (120)

“The remaining problems again concern the language rather than the facts” (122)

“the mathematical scheme of quantum theory can be interpreted as an extension or modification of classical logic” (124)

“For each complementary statement the question whether the atom is left or right is not decided. But the term ‘not decided’ is by no means equivalent to the term ‘not known.’ ‘Not known’ would mean that the atom is ‘really’ left or right, only we do not know where it is. But ‘not decided’ indicates a different situation, expressible only by a complementary statement” (126)

Chapter 11: The Role of Modern Physics in the Present Development of Human Thinking

“Modern physics is just one link in a long chain of events that started form the work of Bacon, Galileo and Kepler and from the practical application of natural science in the seventeenth and eighteenth centuries” (130)

“The connection between natural science and technical science has from the beginning been that of mutual assistance: The progress in technical science, the improvement of the tools, the invention of new technical devices have provided the basis for more, and more accurate, empirical knowledge of nature; and the progress in the understanding of nature and finally the mathematical formulation of natural laws have opened the way to new applications of this knowledge in technical science” (130)

Commentator’s Note: This is what Haraway calls “technoscience.”

“precise knowledge of the mechanical laws was of the greatest value for the improvement of mechanical tools, for the construction of engines” (130)

“The energy stored up in coal, for instance, could then perform some of the work which formerly had to be done by man himself” (130)

Commentator’s Note: industrialization, capitalism.

“science led to a strong preponderance of those nations or states or communities in which this kind of human activity flourished” (131)

“The modern means of communication and of traffic finally completed this process of expansion of technical civilization” (131)

Commentator’s Note: natural > technical > communicational/transportational.

Science “as a biological process on the largest scale” (131)

“Modern physics belongs to the most recent parts of this development, and its unfortunately most visible result, the invention of nuclear weapons” (131)

“anyone who speaks in favor of peace without stating precisely the conditions of this peace must at once be suspected of speaking only about that kind of peace in which he and his group thrive best” (133)

“Any honest declaration for peace must be an enumeration of the sacrifices one is prepared to make for its preservation” (133)

“While political ideas may gain a convincing influence among great masses of people just because they correspond or seem to correspond to the prevailing interests of the people, scientific ideas will spread only because they are true” (134)

Commentator’s Note: This is rather naïve on Heisenberg’s part. Until a paradigm shift, no? This is before Kuhn of course, but Heisenberg has explicitly discussed such a shift from Newtonian mechanics.

“a fundamental complementarity between deliberation and decision” (143)

“The decision finally takes place by pushing away all the arguments—both those that have been understood and others that might come up through further deliberation—and by cutting off all further pondering” (143)

Decision “excludes deliberation. Even the most important decisions in life must always contain this inevitable element of irrationality. The decision itself is necessary” (143)

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