Tag Archives: Douglas Hofstadter

Mathematics and Logic

I continue with the mathematics posts, taking up, as I did in the last, material originally drafted for the first.

Designated for its own post, material can grow, as has the material of this post in the drafting. Large parts of it are taken up with

  1. the notion (due to Collingwood) of criteriological sciences, logic being one of them;

  2. Gödel’s logical theorems of completeness and incompleteness.

I have defined mathematics as the science whose findings are proved by deduction. This definition does not say what mathematics is about. We can say however what logic is about: it is about mathematics quâ deduction. This makes logic a criteriological science, since it seeks, examines, clarifies and limits the criteria whereby we can make deductions. As examples of this activity, Gödel’s theorems are that

  • everything true in all possible mathematical worlds can be deduced;

  • some things true in the world of numbers can never be deduced;

  • the latter theorem is one of those things.

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Multiplicity of Mathematics

I continue with the recent posts about mathematics, which so far have been as follows.

  1. What Mathematics Is”: As distinct from the natural sciences, mathematics is the science whose findings are proved by deduction. I say this myself, and I find it at least implicit in an address by Euphemia Lofton Haynes.

  2. More of What It Is”: Some mathematicians do not distinguish mathematics from physics.

  3. Knottedness”: Topologically speaking, there is a sphere whose outside is not that of a sphere. The example is Alexander’s Horned Sphere, but it cannot actually be physically constructed.

  4. Why It Works”: Why there can be such a thing as the horned sphere.

When I first drafted the first post above, I said a lot more than I eventually posted. I saved it for later, and later is starting to come now.

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Why It Works

The last post, “Knottedness,” constructed Alexander’s Horned Sphere and proved, or sketched the proof, that

  • the horned sphere itself is topologically a sphere, and in particular is simply connected, meaning

    • it’s path-connected: there’s a path from every point to every other point;

    • loops contract to points—are null-homotopic;

  • the space outside of the horned sphere is not simply connected.

This is paradoxical. You would think that if any loop sitting on the horned sphere can be drawn to a point, and any loop outside the horned sphere can be made to sit on the sphere and then drawn to a point, then we ought to be able to get the loop really close to the horned sphere, and let it contract it to a point, just the way it could, if it were actually on the horned sphere.

You would think that, but you would be wrong. Continue reading

Writing, Typography, and Nature

Note added February 10, 2019: I return to this rambling essay, two years later in the Math Village. The main points are as follows.

  • Writing is of value, even if you never again read what you write.
  • There is also value to reading again, as in the present case.
  • A referee rejected a submitted article of mine in the history of mathematics because its order did not make sense—to that referee, though a fellow mathematician thought well of the article. A revision was eventually published as “On Commensurability and Symmetry.”
  • In the preface to The Elements of Typographical Style, Robert Bringhurst wonders how he can write a rulebook when we are all free to be different. He thus sets up an antithesis, such as I would investigate later in “Antitheses.”
  • From being simply a means of copying, typography has become a means of expression.
  • Yet typography should not draw attention to itself, just as, according to Fowler in A Dictionary of Modern English Usage, pronunciation (notably of foreign words) should not.
  • Through my own experience of typography with LaTeX [and HTML, as in this blog], I have developed some opinions differing from some others’.
  • Bringhurst samples Thoreau,
    • whose ridicule of letters sent by post applies today to electronic media, and
    • who rightly bemoans how enjoying the woods is thought idle; cutting them down, productive.
  • In Gödel, Escher, Bach, Douglas Hofstadter wonders how a message can be recognized by any intelligence. Bringhurst restricts the question to concern intelligences on this earth.
  • In my youth, Hofstadter introduced me to Zen Flesh, Zen Bones, (edited by Reps and Senzaki), whose influence on me I consider.
  • The Zen story about whether “this very mind is Buddha” suggests a further development of Collingwood’s “logic of question and answer.”
  • Through looking at another translation, I consider how Reps and Senzaki turned Chinese into English.
  • Rereading this blog led me back to Hofstadter.

Here are some meditations on some books read during a stay in the Nesin Mathematics Village, January, 2017. I originally posted this article from the Village; now, back in Istanbul, a few days into February, recovering from the flu that I started coming down with in the Village, I am correcting some errors and trying to clarify some obscurities.

Nesin Mathematics Village from the east, Wednesday, January 18, 2017
Nesin Mathematics Village from the east
Wednesday, January 18, 2017

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