Donald Knuth, Doron Zeilberger, Stephen Hawking, Timothy Gowers, Andrey Kolmogorov, Harvey Friedman, Philip Davis, Reuben Hersh, John McCarthy, Hugh Woodin, John von Neumann, Max Planck, Benjamin Peirce, Paul Bernays, Edward Nelson, Hilary Putnam, Alan Turing, Michael Aschbacher, Alfred Tarski, Jan Mycielski, Gauss, Daniel Dennett, Richard Feynman, Niels Bohr, Nancy Cartwright, Werner Heisenberg, Alan Musgrave, Bertrand Russell, Philip Anderson, Justus von Liebig, Albert Einstein, Akihiro Kanamori, David Hestenes, Vladimir Sazonov, Antony Jay, Roger Bishop Jones, David Ruelle, Ernest Gellner, Julio Gonzalez Cabillon
Quote of the Day |
Andrey Kolmogorov, 1969. Finite creatures in a finite world may be forced to invent infinity. "... let us imagine an intelligent creature living in a world of finite complexity, [a world] taking only a finite number of physically distinct states and evolutioning in a "discrete time". ... It is possible to explain plausibly how such a creature, because of its structure, being unable to cover all the complexity of the world around it and confronted with systems of growing complexity and consisting of very large numbers of elements, will create during the process of its entirely practically and reasonably oriented activities the concept of an infinite sequence of natural numbers." (Sorry, my own English translation.) The
original text: |
Timothy Gowers, 2011. Observation/Discovery vs. Creation/Invention "... the distinction between discovery and observation is not especially important: if you notice something, then that something must have been there for you to notice, just as if you discover it then it must have been there for you to discover. So let us think of observation as a mild kind of discovery rather than as a fundamentally different phenomenon. " (p. 4) "... we do not normally talk of inventing a single work of art. However, we do not discover it either: a commonly used word for what we do would be ‘create’. And most people, if asked, would say that this kind of creation has more in common with invention than with discovery, just as observation has more in common with discovery than with invention." (p. 5) Full
text: My comment: Thus, the distinction observation/creation is more fundamental than the (rather psychological) one of discovery/invention. And, the right question to ask is not: “Is mathematics discovered or invented?”, but “Is mathematics observed or created?” |
Stephen W. Hawking, 2002. We and our models are both part of the universe. “... we are not angels, who view the universe from the outside. Instead, we and our models are both part of the universe we are describing.” Full
text: |
Akihiro Kanamori, 2009-2013. The carriers of mathematical knowledge are proofs.
“What brings us mathematical knowledge? The carriers of mathematical knowledge are proofs, more generally arguments and constructions, as embedded in larger contexts.1 Mathematicians and teachers of higher mathematics know this, but it should be said. Issues about competence and intuition can be raised as well as factors of knowledge involving the general dissemination of analogical or inductive reasoning or the specific conveyance of methods, approaches or ways of thinking. But in the end, what can be directly conveyed as knowledge are proofs.”
Full
text: |
Albert Einstein, 1930. Knowledge cannot spring from experience alone.
"It seems that the human mind has first to construct forms independently, before we can find them in things. Kepler’s marvelous achievement is a particularly fine example of the truth that knowledge cannot spring from experience alone, but only from the comparison of the inventions of the intellect with observed fact."
English
translation by Sonja
Bargmann published in: German
original: Full
text: |
Justus von Liebig, 1865. Knowledge cannot spring from experience alone.
“Die Erfindung der Elektrisirmaschine, des Elektrophors, der Leydener Flasche, der Volta'schen Säule, die drei Kepler'schen Gesetze sind durch Combinationen der Einbildungskraft erworben worden; ebenso verhält es sich mit den Verfahrungsweisen zur Gewinnung der Metalle, welche, wie die des Eisens aus den Eisensteinen, des Silbers aus den Bleierzen, des Kupfers aus den Kupfererzen etc., zu den verwickeltsten Processen gehören. Die Ueberführung des Eisens in Stahl, des Kupfers in Messing, die Verwandlung der Haut in Leder, des Fettes in Seife, die des Kochsalzes in Soda und tausend ähnliche wichtige Erfindungen sind von Menschen gemacht worden, welche keine oder eine ganz falsche Vorstellung von der eigentlichen Natur der Dinge oder den Vorgängen hatten, an die sich ihre Ideencombination knüpfte. [p. 6, marked bold by me, K.P.] ... “Oft ist die Idee, von der sie ausgingen, ganz falsch, und es wird die richtige erst in der Untersuchung erweckt. Daher denn die Meinung mancher der grössten Forscher, dass die Arbeit alles mache, und dass jede Theorie zu Entdeckungen führe, vorausgesetzt, dass sie zur Arbeit antreibt.” [p. 8, marked bold by me, K.P.] Full text: J. von Liebig. Induktion und Deduktion. Akademische Rede, München 1865 (available online, google for von liebig induktion). |
Karlis Podnieks. February 2010. Human minds... “Everything that is going on in human minds can be best understood as modeling.” Exposition
of the idea: |
Philip W. Anderson, 1972. Reductionism does not imply “constructionism”.
“... the reductionist hypothesis does not by any means imply a “constructionist” one: The ability to reduce everything to simple fundamental laws does not imply the ability to start from those laws and reconstruct the universe.” ... “The constructionist hypothesis breaks down when confronted with the twin difficulties of scale and complexity. ..., at each level of complexity entirely new properties appear, and the understanding of the new behaviors requires research which I think is as fundamental in its nature as any other.” Full text: |
Philip W. Anderson, 1994. At the frontier of complexity, the watchword is not reductionism but emergence.
“But another large fraction [of physicists - K.P.] are engaged in an entirely different type of fundamental research: research into phenomena that are too complex to be analyzed straightforwardly by simple application of the fundamental laws. These physicists are working at another frontier between the mysterious and the understood: the frontier of complexity. At this frontier, the watchword is not reductionism but emergence. Emergent complex phenomena are by no means in violation of the microscopic laws, but they do not appear as logically consequent on these laws.” ... “(ii) One may make a digital computer using electrical relays, vacuum tubes, transistors, or neurons; the latter are capable of behaviors more complex than simple computation but are certainly capable of that; we do not know whether the other examples are capable of "mental" phenomena or not. But the rules governing computation do not vary depending on the physical substrate in which they are expressed; hence, they are logically independent of the physical laws governing that substrate.” Full text: |
Bertrand Russell, 1914. Postulates in metaphysics...
“The oneness of the world is an almost undiscussed postulate of most metaphysics. ... Yet I believe that it embodies a failure to effect thoroughly the "Copernican revolution," and that the apparent oneness of the world is merely the oneness of what is seen by a single spectator or apprehended by a single mind.” Full text: Betrand Russell. Mysticism and Logic: and Other Essays, New York: Longmans, Green and Co., 1918 (available online). I would say: moreover, any metaphysics is a theory based on its own postulates, no more than that! Otherwise, we couldn't discuss several different metaphysics simultaneously. |
Haskell B. Curry, 1939. One postulates the existence of an external world...
“On what grounds do we infer the reality say of the table on which I am writing? I understand that one can consistently maintain the view, called solipsism, that physical objects have no reality; i.e., that the sole reality is my sensations. In fact, one does not prove the existence of an external world, one postulates it.” See p. 7 of Haskell B. Curry. Outlines of a Formalist Philosophy of Mathematics. North-Holland, 1951, 80 pp. |
E Brian Davies, 2007. Let Platonism die.
“The beliefs of most Platonists are based on gut instincts – strong convictions reinforced by years of immersion in their subject. ... These studies [scientific investigations of mental processes – K.P.] are proceeding systematically and are beginning to provide a genuine understanding of the basis of our mathematical abilities. They owe nothing to Platonism, whose main function is to contribute a feeling of security in those who are believers. Its other function has been to provide employment for hundreds of philosophers vainly trying to reconcile it with everything we know about the world. It is about time that we recognised that mathematics is not different in type from all our other, equally remarkable, mental skills and ditched the last remnant of this ancient religion.” Full
text: |
E Brian Davies, July 2001, large finite numbers only exist in a metaphysical sense
“... sufficiently large finite numbers only exist in a metaphysical sense: they play no role in science and our only access to them depends upon accepting the rules of Peano arithmetic. ... ... no material object can be said to contain a precise number of atoms if that number is greater than 10^{30}. One may of course consider an ideal silver cube containing exactly 10^{10} atoms along each edge and therefore 10^{30} atoms altogether, but this cube is then a mental construction and not something in the material world. ... For even bigger numbers the situation shifts again. The number of massive elementary particles in the universe is beleived to be less than M=10^{100}. ... If one regards all sets of particles as candidates for material entities then 2^{N} is an upper bound for the number of different material entities. It is a matter of fact that physicists do not make use of numbers vastly bigger than this, and it is difficult to argue that they have any empirical status. ... We consider the real number field of Dedekind and Weierstrass to be metaphysical because its adds features to the physical continuum which have no empirical justification. ... Mathematicians have produced these idealized versions of the empirical continuum because of their need to have sharp formalisms if they are to prove theorems, and because the idealized systems are easier to grasp intuitively.“ Full
text: A similar point of view is expressed in: "Real" Analysis is a Degenerate Case of Discrete Analysis by Doron Zeilberger (appeared in "New Progress in Difference Equations" (Proc. ICDEA 2001), Taylor and Francis, London, 2004) The idea can be traced to Paul Bernays in 1934, for a more detailed history, see Section 1.1 of K. Podnieks. What is Mathematics: Gödel's Theorem and Around, 1997-2012. |
Carl Johannes Thomae, 1898, the true founder of the formalist philosophy of mathematics? “The formal conception of numbers requires of itself more modest limitations than does the logical conception. It does not ask, what are and what shall the numbers be, but it asks, what does one require of numbers in arithmetic. For the formal conception, arithmetic is a game with signs which one may call empty; by this one wants to say that (in the game of calculation) they have no other content than that which has been attributed to them concerning their behaviour with respect to certain rules of combination (rules of the game). Similarly a chess player uses his pieces, he attributes to them certain properties which condition their behaviour in the game, and the pieces themselves are only external signs for this behaviour. To be sure, there is an important difference between the game of chess and arithmetic. The rules of chess are arbitrary; the system of rules for arithmetic is such that by means of simple axioms the numbers can be related to intuitive manifolds, so that they are of essential service in the knowledge of nature. - The formal standpoint relieves us of all metaphysical difficulties, that is the benefit it offers to us.” Quoted after: |
Paul Dirac on interpretations, before 1984 “... Dirac was never interested in interpretations [of quantum theory – K.P.]. It seemed to him to be a pointless preoccupation that led to no new equations.” Full
text: p. 277 of “In these cases, as in the case of quantum mechanics, a very strictly empiricist position could have circumvented the problem [of interpretation – K.P.] altogether, by reducing the content of the theory to a list of predicted numbers. But perhaps science can offer us more than such a list; and certainly science needs more than such a list to find its ways [marked bold by me – K.P.].” Full
text: Thus, interpretations may be useful, but only when they “lead to new equations”. |
Richard Feynman, between 1918 and 1988, Electron is a theory... “The electron is a theory that we use; it is so useful in understanding the way nature works that we can almost call it real. I wanted to make the idea of a theory clear by analogy. In the case of the brick, my next question was going to be, "What about the inside of the brick?" - and I would then point out that no one has ever seen the inside of a brick. Every time you break the brick, you only see the surface. That the brick has an inside is a simple theory which helps us understand things better. The theory of electrons is analogous.” (Fragments marked bold by me – K. P.) Full text – in Chapter 9 of: Surely You're Joking, Mr. Feynman!: Adventures of a Curious Character, with contributions by Ralph Leighton, W. W. Norton & Co, 1985. |
Werner Heisenberg, March 1927, We cannot know the present in all detail. “But what is wrong in the sharp formulation of the law of causality, "When we know the present precisely, we can predict the future," is not the conclusion but the assumption. Even in principle we cannot know the present in all detail.” German original: “Aber an der scharfen Formulierung des Kausalgesetzes: "Wenn wir die Gegenwart genau kennen, koennen wir die Zukunft berechnen", ist nicht der Nachsatz, sondern die Voraussetzung falsch. Wir koennen die Gegenwart in allen Bestimmungstuecken prinzipiell n i c h t kennenlernen.” See p. 198 of: W. Heisenberg. Über den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik, Zeitschrift für Physik, Volume 43, pp. 172-198 (1927), online copy available. English translation: Quantum Theory and Measurement; Wheeler, J. A.; Zurek, W. H., Eds.; Princeton University Press: Princeton, NJ, 1983; pp. 62-84. |
Alan Musgrave, 1989, Deductive logic is the only logic that we have or need! "... reasoners seldom, if ever, state all of the premises they are assuming. We usually, perhaps always, have to reconstruct the arguments being employed. Deductivism is the view that deductive logic is the only logic that we have or need. Deductivists can always reconstruct what look like non-deductive or inductive arguments as deductive arguments with missing premises of one kind or another. ... it conduces to clarity, if we do treat them so. ...if accepted, it would enable us to make good Popper's claim that induction is a myth." See p. 319 of: A. Musgrave. Essays on Realism and Rationalism. Rodopi, Amsterdam-Atlanta, 1999, pp. xiii + 373. |
Stephanie Ruphy, 2008, The Millennium Run – balancing ambition and outcome... “Acknowledging path dependency immediately puts to the fore the contingency of a simulation such as the Millennium Run. Had the cosmologists chosen different options at some stages in the model-building process, they would have come up with a different picture of the evolution of cosmic matter. And the point is that those alternative pictures would be equally plausible in the sense that they would also be consistent both with the observations at hand and with our current theoretical knowledge.” S. Ruphy. Limits to Modeling: Balancing Ambition and Outcome in Astrophysics and Cosmology. In: Simulation & Gaming, first published on June 2008 as doi: 10.1177/ 1046878108319640, Sage Publications. |
Jeff Rothenberg, 1989, We are, ... modelers... Modeling underlies our ability to think and imagine, to use signs and language, to communicate, to generalize from experience, to deal with the unexpected, and to make sense out of the raw bombardment of our sensations. It allows us to see patterns, to appreciate, predict, and manipulate processes and things, and to express meaning and purpose. In short, it is one of the most essential activities of the human mind. It is the foundation of what we call intelligent behavior and is a large part of what makes us human. We are, in a word, modelers: creatures that build and use models routinely, habitually−−sometimes even compulsively−−to face, understand, and interact with reality. Full text: J. Rothenberg. THE NATURE OF MODELING. AI, Simulation & Modeling, John Wiley & Sons, 1989, pp. 75−92. |
Nancy Cartwright, 1983, How the Laws of Physics Lie “My basic view is that fundamental equations do not govern objects in reality; they only govern objects in models.” See p. 129
of: |
[Attributed to] Niels Bohr, before 1963. "There is no quantum world. There is only an abstract quantum physical description. It is wrong to think the task of physics is to find out how nature is. Physics concerns what we can say about nature." Quoted
after: |
Barry Mazur, June 2008, Experience of platonic realms "When I’m working I sometimes have the sense – possibly the illusion – of gazing on the bare platonic beauty of structure or of mathematical objects, and at other times I’m a happy Kantian, marvelling at the generative power of the intuitions for setting what an Aristotelian might call the formal conditions of an object. And sometimes I seem to straddle these camps (and this represents no contradiction to me). I feel that the intensity of this experience, the vertiginous imaginings, the leaps of intuition, the breathlessness that results from “seeing” but where the sights are of entities abiding in some realm of ideas, and the passion of it all, is what makes mathematics so supremely important for me. Of course, the realm might be illusion. But the experience?" My comment: see my explanation below - "What is Mathematics? (My Main Theses)" Full
text: |
Reuben Hersh, June 2008, Mathematics before Big Bang? "I once took a vote in a talk at New Mexico State University in Las Cruces. The question was, “Was the spectral theorem on self-adjoint operators in Hilbert space true before the Big Bang, before there was a universe?” The vote was yes, by a margin of 75 to 25. But there were no self-adjoint operators, no Hilbert space, before the twentieth century!" Full text: |
Deena Skolnick Weisberg on mathematical platonism, about 2008. "To use a phrase suggested by Deena Weisberg, a view of model systems as imagined concrete things which many scientists can simultaneously investigate is the "folk ontology" of model-based science, the ontology that is implicit in the practitioners' routine behaviors. ... an implicitly platonist outlook is a feature of successful mathematical practice – in Weisberg's terms again, ... platonism is the folk ontology of research mathematics." Quoted after: My comment: |
Doron Zeilberger, Computer assisted mathematics, January 2008 "... it is very possible that if Andrew Wiles' programming skills would have been as good as his proving skills, he would have already proved the Riemann Hypothesis." Full text: http://www.math.rutgers.edu/~zeilberg/Opinion94.html. |
Karlis Podnieks. Infinity, January 2006 "Couldn't the invention of the axiom of infinity simply be an act of fantasy?" Full text: [FOM] Infinity and the "Noble Lie". |
Freek Wiedijk. The Future of Formal Mathematics, November 2008 In a few decades it will no longer take one week to formalize a page from an undergraduate textbook. Then that time will have dropped to a few hours. Also then the formalization will be quite close to what one finds in such a textbook. When this happens we will see a quantum leap, and suddenly all mathematicians will start using formalization for their proofs. When the part of refereeing a mathematical article that consists of checking its correctness takes more time than formalizing the contents of the paper would take, referees will insist on getting a formalized version before they want to look at a paper. However, having mathematics become utterly
reliable might not be the primary reason that eventually Full text: |
Richard Feynman. The Nobel Prize in Physics, 1965. "The fact that electrodynamics can be written in so many ways ..., was something I knew, but I have never understood. It always seems odd to me that the fundamental laws of physics, when discovered, can appear in so many different forms that are not apparently identical at first, but, with a little mathematical fiddling you can show the relationship. ... I don't know why this is - it remains a mystery, but it was something I learned from experience. There is always another way to say the same thing that doesn't look at all like the way you said it before. I don't know what the reason for this is. I think it is somehow a representation of the simplicity of nature. ... I don't know what it means, that nature chooses these curious forms, but maybe that is a way of defining simplicity. Perhaps a thing is simple if you can describe it fully in several different ways without immediately knowing that you are describing the same thing." Full text: |
Daniel C. Dennett, 2008 "A point I have often made is that computer science keeps cognitive science honest. If it weren’t for the practical possibility of constructing and demonstrating simplified working models of cognitive processes, we’d still be at the hand-waving stage. ... most of the good work in computer science (and related fields such as robotics) enlarges our appreciation for just how remarkable our brains are. Full text: |
Hilary Putnam: Philosophy of Mathematics: Why Nothing Works? Question asked 1979, the answer of 1997 follows (as put by Wikipedia): "Under the influence of Ludwig Wittgenstein, he [Putnam - K.P.] adopted a pluralist view of philosophy itself and came to view most philosophical problems as nothing more than conceptual or linguistic confusions created by philosophers by using ordinary language out of its original context." Full text: Hilary
Putnam by Wikipedia. |
Donald E. Knuth, 20 May 1995 "Science is what we understand well enough to explain to a computer. Art is everything else we do." Full text: |
David Hestenes, 1992, [models are invented, it is their fitness to data that is discovered!]: "Kepler employed the Copernican reference system in his own analysis and showed that Tycho's more accurate data could not be fitted to the Copernican model. ... Since no one before had ever considered any kinematical alternative to uniform circular motion, Kepler had to invent his own to fit the data. His brilliant result is formulated as a system of functional relations called Kepler's laws. Many physicists would insist that Kepler's laws were discovered rather than invented. On the contrary, what Kepler discovered was that these laws fit the data. He had considered and discarded many alternatives. It would be better to speak of Kepler's model (rather than laws) and say that the model has been validated to the precision in Tycho's observations. We now know that many alternative models could be invented to fit the same data, but Kepler's is the simplest of all models in this class. We also know that Kepler's could not fit the more accurate data collected with telescopes rather than the naked eye, because the elliptical planetary orbits are perturbed by gravitational forces from other planets, ... That fact could never be discovered by Kepler's method; the more powerful method of Newton was needed. It is no small irony that Newton's law of gravitation would undoubtedly have been more difficult to discover if Kepler's model had been quickly invalidated by more accurate data. Here we have the possibility that scientific progress might be impeded by greater experimental precision." Full text: |
L E J Brouwer, 19XX "Mathematics is nothing more, nothing less, than the exact part of our thinking." See Quotations by L E J Brouwer in The MacTutor History of Mathematics archive. |
Patrick Suppes, 1978 "... I do want to convey the basic philosophical point that I continue to find the real puzzle of quantum mechanics. Not the move away from classical determinism, but the ways in which the standard versions seem to lie outside the almost universal methodology of modern probability theory and mathematical statistics. For me it is in this arena that the real puzzles of quantum mechanics are to be found. I am philosophically willing to violate classical physical principles without too many qualms, but when it comes to moving away from the broad conceptual and formal framework of modern probability theory I am at once uneasy. My historical view of the situation is that if probability theory had been developed to anything like its current sophisticated state at the time the basic work on quantum mechanics was done in the twenties, then a very different sort of theory would have been formulated." Full
text: "For example, in quantum chemistry there is, with present intellectual and computing resources, no hope of making a direct attack on the behavior of complex molecules by beginning with the first principles of quantum theory. A problem as easy to formulate as that of deriving from first principles the boiling point of water under normal atmospheric pressure is simply beyond solution at the present time and is recognized as such." Full text: p.15. "... On the other hand, I strongly believe that a reduction of psychology to the biological or physical sciences will not occur and is not intellectually feasible. I am not happy with leaving the statement of my views at this level of generality, and I consider it an intellectual responsibility of methodological behaviorists like myself to reach for a deeper and more formal statement of this antireductionist position. What are needed are theorems based on currently reasonable assumptions showing that such a reduction cannot be made. I think of such theorems as being formulated in the spirit in which theorems are stated in quantum mechanics about the impossibility of deterministic hidden variable theories." Full text: p.16. |
Paul Bernays, 1958 "As Bernays remarks, syntax is a branch of number theory and semantics the one of set theory." See p. 470
of |
David Hestenes, 2006 "To
the grand philosophical question: "What
is a man?"
Aristotle answered: "Man
is a rational animal."
Modeling Theory offers a new answer: "Man
is a modeling animal!"
HOMO MODELUS!" |
From: Vladimir
Sazonov "When trying to formalize some new imaginary world (say, of infinite objects - sets) we should realize that it is only imaginary one and nothing is true or false there in the same sense as in the ordinary physical world or for not so big finite objects, and no logical laws hold there just because they are "objectively" true - "do not hold" in this sense. Thus, when we DECIDE to impose the ordinary (or any other preferable) logical laws onto this world, it is not because they are true there. It is because this is OUR decision, assuming it is sufficiently coherent with our imagination and sufficiently robust. (The coherence is typically incomplete; also various surprises - counterexamples - are possible which would rather "correct" our intuition. And we so much respect these formalisms that we usually are quite happy with these corrections.) We create our own worlds and "play" there by the laws of some logic we choose, let Aristotelian." Full text at http://www.cs.nyu.edu/pipermail/fom/2007-July/011784.html |
John McCarthy, February 29, 1996 "It turns out that many philosophical problems take new forms when thought about in terms of how to design a robot." Full text: |
Carl Friedrich Gauss to Franz Adolph Taurinus, Goettingen, November 8, 1824 "... But it seems to me that in spite of the word-mastery of the metaphysicians, we know really too little, or even nothing at all, about the true nature of space to be able to confuse something that seems unnatural with absolutely impossible. If non-Euclidean geometry is the real one and the constant is incomparable to the magnitudes that we encounter on earth or in the heavens then it can be determined aposteriori. I have therefore occasionally for fun expressed the wish that Euclidean geometry not be the real one, for then we would have a priori an absolute measure." Full text: Gauss And Non-Euclidean Geometry by Stanley N. Burris (see also the German original at the Göttinger Digitalisierungs-Zentrum). My comment: |
Aleksandr Danilovic Aleksandrov, about mathematics as a kind of technology, 1970. "Mathematics is creating its apparatus, and speaking about its truth or falsity is senseless: the apparatus is either working, or not working, and if working, it is working either productively, or not. A similar nonsense would be asking: "Is this screwdriver true or false?"; the screwdriver simply exists, and one can only ask sensibly, how is it working, and where could it be applied." (continue here, in Russian, sorry, my own English translation). Full text: |
Hilary Putnam, about "theory-dependence of meaning and truth", December 29, 1977. "It may well be the case that the idea that statements have their truth values independent of embedding theory is so deeply built into our ways of talking that there is simply no "ordinary language" word or short phrase which refers to the theory-dependence of meaning and truth. Perhaps this is why Poincare was driven to exclaim "Convention, yes! Arbitrary, no!" when he was trying to express a similar idea in another context." (p. 471) "... The language, on the perspective we talked ourselves into, has a full program of use; but it still lacks interpretation. This is the fatal step. To adopt a theory of meaning according to which a language whose whole use is specified still lacks something - viz. its "interpretation" - is to accept problem which can only have crazy solutions. To speak as if this were my problem, "I know how to use my language, but, now, how shall I single out an interpretation?" is to speak nonsense. Either the use already fixes the "interpretation" or nothing can." (pp.481-482) Full text: |
Jan Mycielski, at the Russell's Paradox Centennial Conference, Munich, 2001 "... In this state of affairs the existence of Platonists in this day and age is puzzling to us as it was puzzling to Tarski ... and presumably to Russell. ... Of course there were very outstanding Platonists, and among them Frege, Zermelo and Gödel. ..." Full text: |
Alfred Tarski, at the "Tarski Symposium", University of Berkeley, 1971: "People have asked me 'How can you, a nominalist, do work in set theory and logic, which are theories about things you do not believe in?' . . . I believe there is value even in fairy tales and the study of fairy tales." Quoted after: |
From: Timothy
Y. Chow "Any skepticism about the naive (resp. formal) concept of the integers carries over directly into skepticism about the naive (resp. formal) concept of a formal system. Anyone who thinks that formal systems are crystal clear while integers are vague and suspect---and who tries to argue that the existence of nonstandard models lends support to that idea---is simply suffering from a blindspot that prevents him from seeing that his skeptical arguments apply equally to formal systems. " Full text at http://www.cs.nyu.edu/pipermail/fom/2006-October/011009.html From: Vladimir
Sazonov "I definitely do not suffer from such a blindspot. Moreover, I make clear distinction between naive and abstract (meta)mathematical concepts discussed... You are right. Abstract (meta)mathematical formal
systems can have nonstandard formulas and derivations. Exactly the
same as for abstract mathematical numbers. In place of that person I would replace here "standard formal system" by "NAIVE, CONCRETE formal system" because it is continued with "on a sheet of paper". This is not about an abstract (meta)mathematical concept. This is from real human activity of writing symbols, symbolically presented rules and practical ability to follow these rules. No theory explaining this activity is needed. People just are able to do this in practice. That is why this activity is both NAIVE and CONCRETE. " Full text at http://www.cs.nyu.edu/pipermail/fom/2006-October/011018.html My
comment: |
Roger Penrose about Gödel's Incompleteness Theorem, 2005: "... he [Gödel] demonstrated that, if we are prepared to accept that the rules of some such formal system F are to be trusted as giving us only mathematically correct conclusions, then we must also accept, as correct, a certain clear-cut mathematical statement G(F), while concluding that G(F) is not provable by the methods of F alone. Thus, Gödel shows us how to transcend any F that we are prepared to trust." Full text: My
comment: |
Rebecca Goldstein about Kurt Gödel, 2005: "I'm saddened by the sense of his isolation, by how profound it must have been. It's chilling to consider that he felt the world to be so hostile that he believed his food was being poisoned and so stopped eating and so starved to death. I've spent a long time imagining what that must have felt like for such a man. And I contrast that dark and cold place in which he lived many long years and in which he ended his life with the sense of bright wonderment that I experienced that summer before graduate school, when I first understood Gödel's masterpiece of reason. He gave that experience to countless people, and we're grateful." Full
text: |
Michael Aschbacher about probably the most complicated mathematical proof ever, 2004-2005 "To my knowledge the main theorem of [AS] closes the last gap in the original proof, so (for the moment) the Classification Theorem can be regarded as a theorem. On the other hand, I hope I have convinced you that it is important to complete the program by carefully writing out a more reliable proof in order to minimize the chance of other gaps being discovered in the future." Full text: (For the formulation of the Classification Theorem, see Classification of finite simple groups by Wikipedia, the free encyclopedia.) "Conventional wisdom says the ideal proof should be short, simple, and elegant. However there are now examples of very long, complicated proofs, and as mathematics continues to mature, more examples are likely to appear. Such proofs raise various issues. For example it is impossible to write out a very long and complicated argument without error, so is such a ‘proof’ really a proof? What conditions make complex proofs necessary, possible, and of interest? Is the mathematics involved in dealing with information rich problems qualitatively different from more traditional mathematics?" Full text: |
Alan M. Turing about "the real moral of the Gödel result" (February 20, 1947) "As Penrose himself notes, this seems to be what Turing thought was the real moral of the Gödel result. Turing is worth quoting at length:" "It might be argued that there is a fundamental contradiction in the idea of a machine with intelligence. It is certainly true that 'acting like a machine', has come to be synonymous with lack of adaptability... It has for instance been shown that with certain logical systems there can be no machine which will distinguish provable formulae of the system from unprovable... Thus if a machine is made for this purpose it must in some cases fail to give an answer. On the other hand, if a mathematician is confronted with such a problem he would search around and find new methods of proof, so that he ought to be able to reach a decision about any given formula. Against it I would say that fair play must be given to the machine. Instead of it sometimes giving no answer we could arrange it so that it gives occasional wrong answers. But the human mathematician would likewise make blunders when trying out new techniques. It is easy for us to regard these blunders as not counting and give him another chance, but the machine would probably be allowed no mercy. In other words then, if a machine is expected to be infallible, it cannot also be intelligent. There are several mathematical theorems which say almost exactly that. But these theorems say nothing about how much intelligence may be displayed if a machine makes no pretense at infallibility." Quoted after: Rick Grush, Patricia S. Churchland. GAPS IN PENROSE'S TOILINGS. Journal of Consciousness Studies, 1995, vol. 2, N 1, pp. 10-29 (online copy). Full text: |
From: Vladimir
Sazonov " I think that, like in engineering, mathematicians (or just our ancestors when they invented numbers) are really creators of mathematical concepts via formal systems, axioms, definitions, algorithms etc., and, again like in engineering, these creations are not absolutely free. However, they are *potentially* free. There is no restriction to create possibly useless/meaningless formalisms, incorrect proofs, etc. like useless (but may be amazing) engineering devices. I see mathematics in general as the engineering of formal tools (formalisms) strengthening our abstract thought, and it is this what imposes the restriction under discussion. This can be also compared with software engineering which however is devoted to mechanising the routine part of our intellectual activity." Full text at http://www.cs.nyu.edu/pipermail/fom/2006-April/010347.html |
Seth Lloyd about computational capacity of the Universe, 2002 "All physical systems register and process information. The laws of physics determine the amount of information that a physical system can register (number of bits) and the number of elementary logic operations that a system can perform (number of ops). The Universe is a physical system. The amount of information that the Universe can register and the number of elementary operations that it can have performed over its history are calculated. The Universe can have performed 10^{120} ops on 10^{90} bits ( 10^{120} bits including gravitational degrees of freedom)." Full text: |
From Hendrik J. Boom "Practicing physicist seem to act as if every set of real numbers is measurable, for example. This lets them off the escalator of ascending set-theoretic axioms rather early, as they never get around to accepting the axiom of choice. In fact, some physists seem to act as if every total function from R->R is continuous! Does this make them unwitting constructivists?" Full text at http://www.cs.nyu.edu/pipermail/fom/2006-February/009667.html |
Hilary
Putnam about experimental mathematics, 1975 Full text: |
Edward Nelson. Mathematics and Faith. Vatican, May 23-24, 2000 "The notion of truth in mathematics is irrelevant to what mathematicians do, it is vague unless abstractly formalized, and it varies according to philosophical opinion. In short, it is formal abstraction masquerading as reality." Full text at http://www.math.princeton.edu/~nelson/papers.html. |
As a regular term, "platonism in mathematics" is used since the lecture delivered June 18, 1934, University of Geneva, by Paul Bernays: P. Bernays. Sur le platonisme dans les mathematiques. L'enseignement mathematique, Vol. 34 (1935), pp. 52-69. Quoted from English translation by Charles D. Parsons at www.phil.cmu.edu/projects/bernays/Pdf/platonism.pdf. Bernays considers mathematical platonism as a method that can be - "taking certain precautions" - applied in mathematics. Some remarkable quotes (fragments marked bold by me - K. P.): ... allow me to call it "platonism". ... The value of platonistically inspired mathematical conceptions is that they furnish models of abstract imagination. These stand out by their simplicity and logical strength. They form representations which extrapolate from certain regions of experience and intuition. ... This brief summary will suffice to characterize platonism and its application to mathematics. This application is so widespread that it is not an exaggeration to say that platonism reigns today in mathematics. ... Several mathematicians and philosophers interpret the methods of platonism in the sense of conceptual realism, postulating the existence of a world of ideal objects containing all the objects and relations of mathematics. It is this absolute platonism which has been shown untenable by the antinomies, particularly by those surrounding the Russell-Zermelo paradox. ... It is also this transcendent character which requires us to take certain precautions in regard to each platonistic assumption. For even when such a supposition is not at all arbitrary and presents itself naturally to the mind, it can still be that the principle from which it proceeds permits only a restricted application, outside of which one would fall into contradiction. We must be all the more careful in the face of this possibility, since the drive for simplicity leads us to make our principles as broad as possible. And the need for a restriction is often not noticed. This was the case, as we have seen, for the principle of totality, which was pressed too far by absolute platonism. Here it was only the discovery of the Russell-Zermelo paradox which showed that a restriction was necessary. [Inspired by reading: Jacques Bouveresse. On the Meaning of the Word 'Platonism' in the Expression 'Mathematical platonism'. Proceedings of the Aristotelian Society, September 2004, Volume 105, pp. 55-79 (online French version). Thanks to William J. Greenberg.] |
Max
Planck (1858-1947) "Die Wahrheit triumphiert nie, ihre Gegner
sterben nur aus." Condensed version from the article Max Plack in Wikiquote, full text ibid. |
John
von Neumann "I think that it is a relatively good
approximation to truth - which is much too complicated to allow
anything but approximations - that mathematical ideas originate in
empirics, although the genealogy is sometimes long and obscure.
But, once they are so conceived, the subject begins to live a
peculiar life of its own and is better compared to a creative one,
governed by almost entirely aesthetical motivations, than to
anyting else and, in particular, to an empirical science. There
is, however, a further point which, I believe, need stressing. Quoted after the October 22, 1995 posting by Louis A. Talman at Math Forum @ Drexel. |
Antony Jay "In corporation [corporate] religions as in others, the heretic must be cast out not because of the probability that he is wrong but because of the possibility that he is right." - as quoted twice by Edsger W. Dijkstra, February, 27, 1975 and August 11, 1982. |
Doron
Zeilberger, 1993 "The computer has already started doing to mathematics what the telescope and microscope did to astronomy and biology. In the future, not all mathematicians will care about absolute certainty, since there will be so many exciting new facts to discover: mathematical pulsars and quasars that will make the Mandelbrot set seem like a mere Jovian moon. We will have (both human and machine) professional theoretical mathematicians, who will develop conceptual paradigms to make sense out of the empirical data, and who will reap Fields medals along with (human and machine) experimental mathematicians. Will there still be a place for mathematical mathematicians?" Full text appeared in Notices of the AMS, Vol. 40, N8 (October 1993), pp.978-981 (online copy available). |
Roger
Bishop Jones, 2005 "We find ourselves at the beginning of the 21st century facing the prospect that knowledge may no longer be the exclusive domain of human intelligence, and that questions of ontology, mathematics, science and engineering may be entertained and resolved by fabrications in silicon." Online text in progress, February 11, 2005, at http://www.rbjones.com/rbjpub/www/papers/p003.pdf |
David
Ruelle, 1999 "Admittedly, the mathematician's ideas reside in a modest amount of jelly-like substance which constitutes the mathematician's brain, ..." "... because a mathematician's world is a world of ideas as envisioned by Plato. But what comes out of our discussion is that these ideas are very specifically human, depending on the very special organization of our brain, and in particular on its shortcomings." "The fundamental limitations put by physical law on computing, or doing mathematics, do not appear to be very well understood at this time. ... It seems possible, however, that another crisis of foundations of mathematics may be awaiting us, and that collision with physical law could cause further damage to our Platonist conception of mathematics." Johann Bernoulli lecture, Groningen, April 20, 1999, full text at http://www.ihes.fr/~ruelle/PUBLICATIONS/127plato.pdf |
From: Harvey
Friedman ... ... Full text at http://cs.nyu.edu/pipermail/fom/2005-January/008707.html |
David Corfield (2004) ... So much effort has been devoted to a thin
notion of truth, so little to the thicker notion of significance.
To say that scientists and mathematicians aim merely for the truth
is a gross distortion. They aim for significant truths. |
Georg Cantor, August 28, 1899 ... Wilfried Sieg. Hilbert's programs: 1917-1922. The Bulletin of Symbolic Logic, March 1999, Vol.5, N 1 (online copy). |
From: Jeffrey Ketland
... ... If I remember right, the gist is this. In
studying the consistency problem, Gödel wanted initially to
give an interpretation of second-order arithmetic within
first-order arithmetic, and tried to find a definition of
(second-order!) arithmetic truth in the first-order language. He
discovered however that even first-order arithmetic truth is not
arithmetically definable: i.e., what we now call Tarski's
Indefinability Theorem. But, as he also discovered, the concept
"provable-in-F", with F some fixed formal system, is
arithmetically definable. This implies that arithmetic truth is
distinct from provable-in-F, for any formal system F. This then
gives us the quick proof of Gödel's first incompleteness
theorem. Full text at http://cs.nyu.edu/pipermail/fom/2004-August/008432.html |
Benjamin Peirce & Son (1870+) ... in 1870 Benjamin Peirce defined mathematics as "the science that draws necessary conclusions" (see his son C.S.Peirce 1898/1955, p.137). C.S.Peirce himself described the work of a mathematician as composed of two different activities (p.138): (1) framing of a hypothesis stripped of all features which do not concern the drawing of consequences from it, without caring whether this hypothesis agrees with the actual facts; (2) drawing the necessary consequences from the hypothesis. He noted (Peirce 1902/1955, p.144) the difficulty to distinguish between two definitions of mathematics, one by its method ("drawing necessary conclusions"), another by its aim and subject matter ("the study of hypothetical state of things"). See p.5 of |
Philip J. Davis and Reuben Hersh (1987): In the real world of mathematics, a mathematical
paper does two things. It testifies that the author has convinced
himself and his friends that certain "results" are true,
and presents a part of the evidence on which this conviction is
based. [Added December 7, 2008. Thanks to Maris Ozols.] Now, 20 years later, the situation is changing... See Notices of the AMS, Special Issue on Formal Proof, Vol. 55, N 11, 2008 (available online). |
From: John
McCarthy... Maybe physics is inexhaustible, but maybe it isn't. Here's why it might not be. Consider the Life World based on Conway's Life cellular automaton. It has been shown that self-reproducing universal computers are possible as configurations in the Life World. Therefore, one could have physicists in the Life World, but their physics would not be inexhaustible. They could discover or at least conjecture that their fundamental physics was a particular cellular automaton. However, their mathematics could be the same as ours - and therefore inexhaustible. Full discussion thread - see Foundations of Mathematics (FOM) e-mail list. |
The Continuum Hypothesis (I), 2000, by W.
Hugh Woodin Another version: "An important point is that neither Cohen's method of
extension nor Godel's method of restriction affects the arithmetic
statements true in the structures, so the intuition of a true
model of number theory remains unchallenged. See p. 568 of |
From: Harvey
Friedman ... Full text at http://cs.nyu.edu/pipermail/fom/2004-January/007808.html |
Ernest
Gellner |
Date: Fri, 26 Dec 2003 14:44:47 -0300 Context - at http://cs.nyu.edu/pipermail/fom/2003-December/007721.html |
Doron Zeilberger, November 26, 2001 "... the conventional wisdom, fooled by our misleading "physical intuition", is that the real world is continuous, and that discrete models are necessary evils for approximating the "real" world, due to the innate discreteness of the digital computer. Ironically, the opposite is true. The REAL REAL WORLDS (Physical and MATHEMATICAL) ARE DISCRETE. Continuous analysis and geometry are just degenerate approximations to the discrete world, made necessary by the very limited resources of the human intellect. While discrete analysis is conceptually simpler (and truer) than continuous analysis, technically it is (usyally) much more difficult." "Real" Analysis is a Degenerate Case of Discrete Analysis by Doron Zeilberger (appeared in "New Progress in Difference Equations" (Proc. ICDEA 2001), Taylor and Francis, London, 2004) |
Donald Knuth, Doron Zeilberger, Stephen Hawking, Timothy Gowers, Andrey Kolmogorov, Harvey Friedman, Philip Davis, Reuben Hersh, John McCarthy, Hugh Woodin, John von Neumann, Max Planck, Benjamin Peirce, Paul Bernays, Edward Nelson, Hilary Putnam, Alan Turing, Michael Aschbacher, Alfred Tarski, Jan Mycielski, Gauss, Daniel Dennett, Richard Feynman, Niels Bohr, Nancy Cartwright, Werner Heisenberg, Alan Musgrave, Bertrand Russell, Philip Anderson, Justus von Liebig, Albert Einstein, Akihiro Kanamori, David Hestenes, Vladimir Sazonov, Antony Jay, Roger Bishop Jones, David Ruelle, Ernest Gellner, Julio Gonzalez Cabillon