Niels Bohr

It is a great pity that human beings cannot find all of their satisfaction in scientific contemplativeness.

As quoted in Chandra: A Biography of S. Chandrasekhar‎ (1991) by Kameshwar C. Wali, p. 147, 1991

Oh, what idiots we all have been. This is just as it must be.

In response to Frisch & Meitner's explanation of nuclear fission, as quoted in The Physicists - A generation that changed the world (1981) by C.P.Snow, p. 96, 1981

No, no, you are not thinking, you are just being logical.

In response to those who made purely formal or mathematical arguments, as quoted in What Little I Remember (1979) by Otto Robert Frisch, p. 95, 1979

Two sorts of truth: profound truths recognized by the fact that the opposite is also a profound truth, in contrast to trivialities where opposites are obviously absurd.

As quoted by his son Hans Bohr in "My Father", published in Niels Bohr: His Life and Work (1967), p. 328, 1967

How wonderful that we have met with a paradox. Now we have some hope of making progress.

As quoted in Niels Bohr : The Man, His Science, & the World They Changed (1966) by Ruth Moore, p. 196, 1966

Every valuable human being must be a radical and a rebel, for what he must aim at is to make things better than they are.

As quoted in The World of the Atom (1966) by Henry Abraham Boorse and Lloyd Motz, p. 741, 1966

We are all agreed that your theory is crazy. The question that divides us is whether it is crazy enough to have a chance of being correct.

Said to Wolfgang Pauli after his presentation of Heisenberg's and Pauli's nonlinear field theory of elementary particles, at Columbia University (1958), as reported by F. J. Dyson in his paper "Innovation in Physics" (Scientific American, 199, No. 3, September 1958, pp. 74-82; reprinted in "JingShin Theoretical Physics Symposium in Honor of Professor Ta-You Wu," edited by Jong-Ping Hsu & Leonardo Hsu, Singapore; River Edge, NJ: World Scientific, 1998, pp. 73-90, here: p. 84)., 1958

Those who are not shocked when they first come across quantum theory cannot possibly have understood it.

In a 1952 conversation with Heisenberg and Pauli in Copenhagen; quoted in Heisenberg, Werner, Physics and Beyond. (New York: Harper & Row, 1971) p. 206., 1952

Isolated material particles are abstractions, their properties being definable and observable only through their interaction with other systems.

"Atomic Physics and the Description of Nature" (1934), 1934

The great extension of our experience in recent years has brought light to the insufficiency of our simple mechanical conceptions and, as a consequence, has shaken the foundation on which the customary interpretation of observation was based.

Niels Bohr, "Atomic Physics and the Description of Nature" (1934), 1934

We must be clear that when it comes to atoms, language can be used only as in poetry. The poet, too, is not nearly so concerned with describing facts as with creating images and establishing mental connections.

In his first meeting with Werner Heisenberg in early summer 1920, in response to questions on the nature of language, as reported in Discussions about Language (1933); quoted in Defense Implications of International Indeterminacy (1972) by Robert J. Pranger, p. 11, and Theorizing Modernism : Essays in Critical Theory (1993) by Steve Giles, p. 28, 1933

Even the mathematical framework helps nothing, I would first like to understand how Nature avoids the contradictions. (1927)

Quoted in Werner Heisenberg: Die Sprache der Atome (2010) by H. Rechenberg, p. 564., 1927

I consider those developments in physics during the last decades which have shown how problematical such concepts as "objective" and "subjective" are, a great liberation of thought. The whole thing started with the theory of relativity. In the past, the statement that two events are simultaneous was considered an objective assertion, one that could be communicated quite simply and that was open to verification by any observer. Today we know that 'simultaneity' contains a subjective element, inasmuch as two events that appear simultaneous to an observer at rest are not necessarily simultaneous to an observer in motion. However, the relativistic description is also objective inasmuch as every observer can deduce by calculation what the other observer will perceive or has perceived. For all that, we have come a long way from the classical ideal of objective descriptions. In quantum mechanics the departure from this ideal has been even more radical. We can still use the objectifying language of classical physics to make statements about observable facts. For instance, we can say that a photographic plate has been blackened, or that cloud droplets have formed. But we can say nothing about the atoms themselves. And what predictions we base on such findings depend on the way we pose our experimental question, and here the observer has freedom of choice. Naturally, it still makes no difference whether the observer is a man, an animal, or a piece of apparatus, but it is no longer possible to make predictions without reference to the observer or the means of observation. To that extent, every physical process may be said to have objective and subjective features. The objective world of nineteenth-century science was, as we know today, an ideal, limiting case, but not the whole reality. Admittedly, even in our future encounters with reality we shall have to distinguish between the objective and the subjective side, to make a division between the two. But the location of the separation may depend on the way things are looked at; to a certain extent it can be chosen at will. Hence I can quite understand why we cannot speak about the content of religion in an objectifying language. The fact that different religions try to express this content in quite distinct spiritual forms is no real objection. Perhaps we ought to look upon these different forms as complementary descriptions which, though they exclude one another, are needed to convey the rich possibilities flowing from man's relationship with the central order.

1927

In mathematics we can take our inner distance from the content of our statements. In the final analysis mathematics is a mental game that we can play or not play as we choose. Religion, on the other hand, deals with ourselves, with our life and death; its promises are meant to govern our actions and thus, at least indirectly, our very existence. We cannot just look at them impassively from the outside. Moreover, our attitude to religious questions cannot be separated from our attitude to society. Even if religion arose as the spiritual structure of a particular human society, it is arguable whether it has remained the strongest social molding force through history, or whether society, once formed, develops new spiritual structures and adapts them to its particular level of knowledge. Nowadays, the individual seems to be able to choose the spiritual framework of his thoughts and actions quite freely, and this freedom reflects the fact that the boundaries between the various cultures and societies are beginning to become more fluid. But even when an individual tries to attain the greatest possible degree of independence, he will still be swayed by the existing spiritual structures — consciously or unconsciously. For he, too, must be able to speak of life and death and the human condition to other members of the society in which he's chosen to live; he must educate his children according to the norms of that society, fit into its life. Epistemological sophistries cannot possibly help him attain these ends. Here, too, the relationship between critical thought about the spiritual content of a given religion and action based on the deliberate acceptance of that content is complementary. And such acceptance, if consciously arrived at, fills the individual with strength of purpose, helps him to overcome doubts and, if he has to suffer, provides him with the kind of solace that only a sense of being sheltered under an all-embracing roof can grant. In that sense, religion helps to make social life more harmonious; its most important task is to remind us, in the language of pictures and parables, of the wider framework within which our life is set.

1927

I feel very much like Dirac: the idea of a personal God is foreign to me. But we ought to remember that religion uses language in quite a different way from science. The language of religion is more closely related to the language of poetry than to the language of science. True, we are inclined to think that science deals with information about objective facts, and poetry with subjective feelings. Hence we conclude that if religion does indeed deal with objective truths, it ought to adopt the same criteria of truth as science. But I myself find the division of the world into an objective and a subjective side much too arbitrary. The fact that religions through the ages have spoken in images, parables, and paradoxes means simply that there are no other ways of grasping the reality to which they refer. But that does not mean that it is not a genuine reality. And splitting this reality into an objective and a subjective side won't get us very far.

1927