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Some famous quotes often give interesting insights into the vision of mathematics that certain mathematicians have. Which ones are you particularly fond of?

Standard community wiki rules apply: one quote per post.

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    $\begingroup$ There are 10 kinds of people in the world, those that understand binary and the other 9. $\endgroup$ Nov 30, 2009 at 5:29
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    $\begingroup$ Why did a question with so much positive feedback get closed? $\endgroup$
    – Romeo
    Nov 28, 2010 at 23:21
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    $\begingroup$ Diminishing marginal utility. $\endgroup$ Jan 31, 2011 at 2:46
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    $\begingroup$ Closing this solved what problem? $\endgroup$
    – Matt Brin
    Jan 18, 2012 at 18:35
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    $\begingroup$ @Matt: standards for what kind of questions people want on MO have changed over time, and keeping this question opens gives a false impression to new users of what kind of questions we want on MO. It's less confusing to close it. This happens on other SE sites as well; many of the most popular questions on StackOverflow, for example, are also closed. There's also the more practical issue that if it's open people keep adding answers and, again, the marginal utility of each additional answer is decreasing. $\endgroup$ Nov 12, 2013 at 3:03

94 Answers 94

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I heard this one while taking a differential geometry class in Mexico City. I love it.

"Groups, as men, will be known by their actions".

-Guillermo Moreno.

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  • $\begingroup$ I recall reading about this quote on a book, but I couldn't find any reference about its origin.. can you provide one? $\endgroup$
    – Dinisaur
    Jun 12, 2023 at 14:48
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"If people do not believe that mathematics is simple, it is only because they do not realize how complicated life is." --- John von Neumann. (From a 1947 ACM keynote, recalled by Alt in this 1972 CACM article.)

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    $\begingroup$ I love this quote very much. I myself have compared our life with mathematics I am doing and reached the same conclusion. $\endgroup$
    – Sunni
    Mar 26, 2010 at 3:31
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“The difference between mathematicians and physicists is that after physicists prove a big result they think it is fantastic but after mathematicians prove a big result they think it is trivial.” Lucien Szpiro during Algebra 1 lecture.

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    $\begingroup$ This reminds me of Surely You're Joking, Mr. Feynman!, in which the physics grad students at Princeton propose the theorem that mathematicians only prove trivial theorems. $\endgroup$ Jan 8, 2010 at 6:27
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    $\begingroup$ I once heard Henry McKean say of mathematical models in physics that "First, they’re pretty disgraceful. Second, they work extremely well...One of the faults of mathematicians is: when physicists give them an equation, they take it absolutely seriously." (I wrote this down on the spot.) $\endgroup$ Apr 23, 2010 at 15:48
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    $\begingroup$ Notable counterexample: The existence of the monster group. I think Conway has said that no one quite understands "why" it exists. $\endgroup$ Mar 7, 2017 at 20:55
  • $\begingroup$ @user2204 - I used to tell my students that one of the hardest things about teaching mathematics was that once you understand something it is obvious, but, for the student, before you understand it is as clear as mud. $\endgroup$ Mar 10, 2021 at 15:48
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"Mathematics is the art of giving the same name to different things." Henri Poincaré.

(This was in response to "Poetry is the art of giving different names to the same thing.")

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We often hear that mathematics consists mainly of "proving theorems." Is a writer's job mainly that of "writing sentences?" - Gian-Carlo Rota

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    $\begingroup$ Depends on the writer? $\endgroup$ Nov 30, 2009 at 13:47
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    $\begingroup$ Similarly, depends on the mathematician.... $\endgroup$
    – Suvrit
    Feb 1, 2011 at 18:04
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Oh, he seems like an okay person, except for being a little strange in some ways. All day he sits at his desk and scribbles, scribbles, scribbles. Then, at the end of the day, he takes the sheets of paper he's scribbled on, scrunches them all up, and throws them in the trash can. --J. von Neumann's housekeeper, describing her employer.

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    $\begingroup$ The weatherman at Kitty Hawk thought Wilbur Wright wasted a lot of time watching gulls fly. And Darwin's housekeeper thought he would get more work done if he didn't keep staring at the ants in an anthill. $\endgroup$ Nov 30, 2009 at 1:22
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    $\begingroup$ That's fantastic! $\endgroup$ Nov 30, 2009 at 18:27
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"The introduction of the cipher 0 or the group concept was general nonsense too, and mathematics was more or less stagnating for thousands of years because nobody was around to take such childish steps..."

-Alexander Grothendieck, writing to Ronald Brown

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    $\begingroup$ Grothendieck was French, and I suppose the correct translation would be "digit" not "cipher". $\endgroup$
    – Tom Ellis
    Feb 1, 2011 at 9:39
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    $\begingroup$ As far as I know, Grothendieck is still French. $\endgroup$ Nov 7, 2011 at 15:23
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    $\begingroup$ As far as I know, Grothendieck does not hold any nationality. But I may well be wrong. $\endgroup$ Oct 19, 2012 at 8:52
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    $\begingroup$ I think that Grothendieck was (alas!) French citizen since the 1980s. See Cartier: xahlee.info/math/i/Alexander_Grothendieck_cartier.pdf Footnote 12. $\endgroup$ Apr 20, 2015 at 17:41
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    $\begingroup$ The question is, what "childish steps" do today's mathematicians need to take? $\endgroup$ Sep 2, 2015 at 2:20
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Dieudonné in "Foundations of Modern Analysis, Vol. 1":

There is hardly any theory which is more elementary [than linear algebra], in spite of the fact that generations of professors and textbook writers have obscured its simplicity by preposterous calculations with matrices.

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    $\begingroup$ I wish I could up-vote this a few more times (I know, I'm really slow reading this one)! $\endgroup$ Feb 1, 2011 at 2:47
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It's hard to beat John Stembridge's page of quotes. My single favorite one on this page: "If I have not seen as far as others, it is because there were giants standing on my shoulders." - Hal Abelson.

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    $\begingroup$ Along those lines, R. W. Hamming said "Mathematicians stand on each other’s shoulders while computer scientists stand on each other’s toes." $\endgroup$ Nov 30, 2009 at 3:02
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    $\begingroup$ My version of this quote, after working my way backwards through a series of papers, each relying on the previous ones: If I can't see a darn thing it's because I stand on the shoulders of giants... $\endgroup$ Dec 2, 2009 at 5:49
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    $\begingroup$ What was Gell-Mann's version? Something like, "If I have seen farther than others, it's because I'm surrounded by pygmies?" $\endgroup$
    – Todd Trimble
    Jan 31, 2011 at 1:15
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    $\begingroup$ The way I heard it: "If I have not seen as far as others, it is because I have stood in the footprints of giants." $\endgroup$
    – bof
    Dec 5, 2014 at 1:35
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"The Axiom of Choice is obviously true, the well-ordering principle obviously false, and who can tell about Zorn's lemma?" — Jerry Bona

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    $\begingroup$ Obviously there is something wrong with ZF for proving their equivalence. I blame infinity. $\endgroup$ Nov 30, 2009 at 1:36
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    $\begingroup$ Zorn's Lemma seems the most intuitive out of the three, but well-ordering isn't so counter-intuitive, since all it comes down to is being able to well-order a set with cardinality strictly larger than the natural numbers. Thinking about well-ordering the reals gives a false impression of the difficulty, since the well-ordering only has to do with the underlying set. $\endgroup$ Nov 30, 2009 at 6:25
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    $\begingroup$ @Harry: I can't really agree with either statement. Naively, if we could truly "see" a well-ordering of a set of continuum cardinality, then intuitively we should be able to compare it to $\aleph_1$ and "see" whether it is larger. $\endgroup$
    – Todd Trimble
    Jul 3, 2011 at 12:07
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You know, for a mathematician, he did not have enough imagination. But he has become a poet and now he is fine.

D. Hilbert, talking about an ex-student. I'd love to remember where I got this from!

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  • $\begingroup$ This sounds like it's from the Apology. $\endgroup$ Nov 29, 2009 at 21:08
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    $\begingroup$ You might have gotten it from the Monthly in 1993, or a mailing list or blog that derives from that source. Google Books traces it back to a book about Ernst Cassirer published in 1949. Since it is quoted there as Cassirer's verbal story, it's less clear what Hilbert himself said. archive.org/stream/philosophyoferns033109mbp/… $\endgroup$ Nov 29, 2009 at 22:14
  • $\begingroup$ I seem to recall it being in one of the 10^150 popular books on the Riemann Hypothesis or Fermat's Last Theorem I read when I was younger, but I don't know that I can narrow it down any further than that. $\endgroup$ Nov 29, 2009 at 22:58
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    $\begingroup$ This story is mentioned in Constance Reid's lovely biography "Hilbert". $\endgroup$
    – Lea M
    May 16, 2011 at 4:27
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Not famous yet, maybe from now on!

At a purely formal level, one could call probability theory the study of measure spaces with total measure one, but that would be like calling number theory the study of strings of digits which terminate.

Terence Tao

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"The art of doing mathematics is finding that special case that contains all the germs of generality." -- David Hilbert

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Le but de cette thèse est de munir son auteur du titre de Docteur.

Beginning of A. Douady's thesis. Quoted by Michèle AUdin in her Conseils aux auteurs de textes mathématiques.

In a less barbarous language: The purpose of this thesis is to obtain the degree of Doctor for its author.

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    $\begingroup$ "The goal of this thesis is to furnish its author with the title of Doctor" is perhaps closer still. A. Douady was indeed a rather interesting person! [He was my co-supervisor, along with John Hubbard]. $\endgroup$ Mar 26, 2010 at 2:30
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    $\begingroup$ the sentence ends with : "and (some set) with (some structure)", playing on the two meanings of "munir" = furnish $\endgroup$ Aug 24, 2011 at 3:04
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    $\begingroup$ @FeldmannDenis A wild zeugma has appeared! $\endgroup$ Aug 4, 2022 at 14:40
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Algebra is the offer made by the devil to the mathematician...All you need to do, is give me your soul: give up geometry --Michael Atiyah

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    $\begingroup$ A quote that obviously inspired the soul theorem. en.wikipedia.org/wiki/Soul_theorem $\endgroup$ Dec 18, 2009 at 7:24
  • $\begingroup$ This comment was in an article on 20th century mathematics which did not contain the words "category", but did talk about the unification of mathematics, which has been one of the major contributions of category theory. There is not really a duality between algebra and geometry, as Grothendieck has shown, but there is a search for underlying processes. $\endgroup$ Aug 9, 2012 at 15:37
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    $\begingroup$ @Ronnie, maybe there is no such duality in mathematics, but there is duality in our perception. $\endgroup$ Aug 9, 2012 at 23:35
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    $\begingroup$ @GregKuperberg: do you have any clue that why Cheeger and Gromoll called it soul? $\endgroup$
    – C.F.G
    Sep 9, 2020 at 12:36
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    $\begingroup$ I think that "soul" amounts an alternative word for "core" in this context. "Soul" or "core" just means a canonical, usually smaller middle part, like an apple core. Elsewhere in geometry and topology, people talk about compact cores of spaces, in particular compact cores of 3-manifolds, which is a similar albeit not identical construction. Another construction which is again similar but not identical is the maximal compact subgroup of a Lie group. "Soul" happens to be a bit pompous compared to other names for this type of thing. $\endgroup$ Sep 10, 2020 at 17:04
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Combinatorics is an honest subject. No adèles, no sigma-algebras. You count balls in a box, and you either have the right number or you haven’t. You get the feeling that the result you have discovered is forever, because it’s concrete. Other branches of mathematics are not so clear-cut. Functional analysis of infinite-dimensional spaces is never fully convincing; you don’t get a feeling of having done an honest day’s work. Don’t get the wrong idea – combinatorics is not just putting balls into boxes. Counting finite sets can be a highbrow undertaking, with sophisticated techniques.

Gian-Carlo Rota, in an interview with David Sharp.

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    $\begingroup$ Here is an online copy: fas.org/sgp/othergov/doe/lanl/pubs/00326965.pdf $\endgroup$
    – Jose Capco
    Nov 30, 2009 at 11:11
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    $\begingroup$ like blue collar versus cubicle $\endgroup$
    – Yoo
    Jan 7, 2010 at 18:56
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    $\begingroup$ Combinatorics is discrete functional analysis in my world view, while functional analysis is applied combinatorics. $\endgroup$ Mar 21, 2010 at 19:28
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    $\begingroup$ Bill, would you mind elaborating? As someone not particularly familiar with either field, I can imagine that by combinatorics being "discrete functional analysis" you mean e.g. generating function methods, or perhaps the general ambition of associating some sort of linear operator to combinatorial objects (e.g. adjacency matrix). But what do you mean by functional analysis being applied combinatorics. $\endgroup$
    – Erik Davis
    Apr 15, 2010 at 1:01
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    $\begingroup$ It takes balls to do combinatorics. $\endgroup$
    – Todd Trimble
    Jan 31, 2011 at 1:45
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"God exists since mathematics is consistent, and the Devil exists since we cannot prove it."- André Weil

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    $\begingroup$ So, mathematics is consistent? I think we can more or less rely on dividing by three, for the rest we shouldn't be that sure... $\endgroup$
    – Jose Brox
    Dec 8, 2009 at 15:42
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    $\begingroup$ @Jose: I don't know if you were referring to this paper indirectly, but you should check out math.dartmouth.edu/~doyle/docs/three/three.pdf, where it is proven that division by three is possible. $\endgroup$ Apr 23, 2010 at 12:42
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"It is impossible to separate a cube into two cubes, or a fourth power into two fourth powers, or in general, any power higher than the second into two like powers. I have discovered a truly marvellous proof of this, which this margin is too narrow to contain."

Pierre de Fermat

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    $\begingroup$ This one should definitely have more votes! $\endgroup$
    – Jose Brox
    Dec 8, 2009 at 15:48
  • $\begingroup$ The question is that, if someone provides evidence that all tools available at Fermat's time were not able to prove his conjecture, then Fermat's 'marvellous proof' was wrong. $\endgroup$
    – Sunni
    Mar 26, 2010 at 4:01
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"It is my experience that proofs involving matrices can be shortened by 50% if one throws the matrices out."

-Emil Artin, Geometric Algebra

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Grothendieck comparing two approaches, with the metaphor of opening a nut: the hammer and chisel approach, striking repeatedly until the nut opens, or just letting the nut open naturally by immersing it in some soft liquid and let time pass:

"I can illustrate the second approach with the same image of a nut to be opened. The first analogy that came to my mind is of immersing the nut in some softening liquid, and why not simply water? From time to time you rub so the liquid penetrates better, and otherwise you let time pass. The shell becomes more flexible through weeks and months—when the time is ripe, hand pressure is enough, the shell opens like a perfectly ripened avocado! A different image came to me a few weeks ago. The unknown thing to be known appeared to me as some stretch of earth or hard marl, resisting penetration... the sea advances insensibly in silence, nothing seems to happen, nothing moves, the water is so far off you hardly hear it... yet it finally surrounds the resistant substance."

Grothendieck, of course, always pioneered this approach, and considered for example that Jean-Pierre Serre was a master of the "hammer and chisel" approach, but always solving problems in a very elegant way.

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    $\begingroup$ A friend who I won't name at the moment once told me this, paraphrased: An excellent problem-solver might not always be a great mathematician, while a bad problem-solver can still be an okay mathematician. On the other hand, a good Grothendieck is a great mathematician, while a bad Grothendieck is really terrible! $\endgroup$ Dec 18, 2009 at 7:20
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    $\begingroup$ Greg, the symmetry in that statement would be nicer if you replaced "problem-solver" with "Erdos." $\endgroup$ Dec 27, 2009 at 8:11
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    $\begingroup$ That's a good suggestion, but I can't edit comments. So let me just rephrase the aphorism: "An excellent Erdos might reach certain limits as a mathematician, while a bad Erdos can still be an okay mathematician. On the other hand, a good Grothendieck can be a truly great mathematician, while a bad Grothendieck is really terrible." $\endgroup$ Jan 19, 2010 at 19:36
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"Everyone knows what a curve is, until he has studied enough mathematics to become confused through the countless number of possible exceptions", F. Klein (from Reed & Simon: Methods of modern mathematical physics)

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"Algebraic geometry seems to have acquired the reputation of being esoteric, exclusive, and very abstract, with adherents who are secretly plotting to take over all the rest of mathematics. In one respect this last point is accurate." - David Mumford

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    $\begingroup$ So you guys are trying to take over the rest of mathematics? And I thought I was just paranoid. $\endgroup$ Nov 30, 2009 at 0:33
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    $\begingroup$ A professor of mine recently said something along the lines of, "Liking algebraic geometry is a clich\'e". $\endgroup$ Nov 30, 2009 at 6:30
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"The shortest path between two truths in the real domain passes through the complex domain." -- Jacques Hadamard

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  • $\begingroup$ I saw this quote first at Klein's <Mathematical Thought from Ancient to Modern Times>. However, evidence I have come across is insufficient to show this (shortest path). It is a good question to convince people like me the truth of Sir Hadamard's assertion. $\endgroup$
    – Sunni
    Mar 26, 2010 at 3:43
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    $\begingroup$ Here's a simple example. What is the radius of convergence for the power series of 1/(x^2 + 1) centered at 0? Looking only at the real line there's no apparent reason for the radius to be only 1. But in the complex plane, you can see that the radius is 1 because that's the distance from the center to the singularity at i. Another example would be using contour integration to compute integrals over the real line. $\endgroup$ Mar 26, 2010 at 18:35
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In mathematics you don't understand things. You just get used to them.

--John von Neumann, reply to a physicist at Los Alamos who had said "I don't understand the method of characteristics."

---- footnote on page 226 of Gary Zukav, The Dancing Wu Li Masters: An Overview of the New Physics, Rider, London, 1990.

(taken from Warren Dicks' Home Page)

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    $\begingroup$ I don't know how much I agree with that. It may be true about physics, but not math. $\endgroup$ Nov 30, 2009 at 6:20
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    $\begingroup$ I feel that it's true of both mathematics and physics, but when talking about mathematics it's a much deeper statement. $\endgroup$
    – Dan Piponi
    Dec 2, 2009 at 19:37
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    $\begingroup$ I may have a surprise for you... "Understanding"="getting used to"! :) $\endgroup$
    – M.G.
    Dec 4, 2009 at 21:20
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    $\begingroup$ I totally disagree with this quote ... $\endgroup$ Feb 2, 2010 at 15:45
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    $\begingroup$ It took some time to get used to this quote, but now I understand it… $\endgroup$
    – jmc
    Dec 16, 2014 at 14:18
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"The question you raise, "how can such a formulation lead to computations?" doesn't bother me in the least! Throughout my whole life as a mathematician, the possibility of making explicit, elegant computations has always come out by itself, as a byproduct of a thorough conceptual understanding of what was going on. Thus I never bothered about whether what would come out would be suitable for this or that, but just tried to understand - and it always turned out that understanding was all that mattered." - Grothendieck

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    $\begingroup$ Dear Sam, Do you have the source for this? Best wishes, Matthew $\endgroup$
    – Emerton
    Sep 8, 2011 at 2:15
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    $\begingroup$ It was in a letter to Ronnie Brown - see pages.bangor.ac.uk/~mas010/pstacks.htm. $\endgroup$ Sep 8, 2011 at 11:32
  • $\begingroup$ Dear Sam, Thanks very much! Best wishes, Matthew $\endgroup$
    – Emerton
    Sep 8, 2011 at 14:05
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"In these days the angel of topology and the devil of abstract algebra fight for the soul of every individual discipline of mathematics." - Weyl

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    $\begingroup$ I never understood this quote, I mean, there's nasty algebra and nice algebra, so isn't that statement a bit strong? $\endgroup$ Nov 30, 2009 at 6:28
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    $\begingroup$ I actually think it refers to something Mephistophelian about algebra, as if such heights of abstraction are meant not for mortals, or such symbolic calculation lacks intuitive "soul". (That would be a tendentious way of putting it!) $\endgroup$
    – Todd Trimble
    Jan 31, 2011 at 1:39
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    $\begingroup$ Oh, and I swear that I wrote that before seeing Anton Petrunin's contribution! $\endgroup$
    – Todd Trimble
    Jan 31, 2011 at 1:42
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    $\begingroup$ Weyl surely loves to talk about the devil. $\endgroup$
    – Niemi
    Nov 18, 2012 at 11:45
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" Last time, I asked: "What does mathematics mean to you?" And some people answered: "The manipulation of numbers, the manipulation of structures." And if I had asked what music means to you, would you have answered: "The manipulation of notes?" "- Serge Lang

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  • $\begingroup$ This is from Serge Lang:The Beauty of Doing Mathematics: Three Public Dialogues. $\endgroup$
    – zionpi
    Feb 2, 2019 at 1:44
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"The price of metaphor is eternal vigilance." Norbert Wiener.

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    $\begingroup$ I liked this one; it is pretty deep. $\endgroup$
    – Jose Brox
    Jun 21, 2010 at 7:00
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The introduction of numbers as coordinates is an act of violence.

Hermann Weyl, Philosophy of Mathematics and Natural Science.

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    $\begingroup$ Cannot agree more. $\endgroup$ Dec 1, 2009 at 5:22
  • $\begingroup$ I'm very interested in this quote, but unable to understand. Could you please explain it? $\endgroup$
    – Akira
    Jul 22, 2020 at 18:05
  • $\begingroup$ @LEAnhDung coordinates are not intrinsic to a space, so their introduction can be contrived and hide a deeper understanding of concepts. $\endgroup$
    – Eric
    May 26, 2021 at 6:10
  • $\begingroup$ Yet without this "violence" progress would have been delayed, if at all possible. $\endgroup$
    – Allawonder
    Oct 14, 2023 at 6:18
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“This remarkable conjecture relates the behaviour of a function L, at a point where it is not at present known to be defined, to the order of a group \Sha, which is not known to be finite.”

-John Tate on the Birch-Swinnerton-Dyer Conjecture

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    $\begingroup$ Thank you! I've been trying to track down the wording of this quote for awhile now. $\endgroup$ Jan 16, 2010 at 14:23
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    $\begingroup$ Last year our distinguished Cantrell Lecture series was given by Dick Gross. I had been booked as a speaker in the graduate student seminar, which took place immediately before Gross's first lecture. I decided to give an introduction to elliptic curves, including BSD and Gross-Zagier. I made sure to include this quote of Tate. So did Gross in his first lecture. $\endgroup$ Mar 26, 2016 at 20:17

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