Just learned: next autumn I shall be again teaching my course on the Philosophy and Logic of Games! What fun it was last time, and I hope it will be again. Last year, we studied theory, philosophical essays, infinite games, determinacy, actual games, everything.

Hitting a highlight, we ascended into Hilbert's Grand Hotel in my Infinity class. #TheBookOfInfinity www.infinitelymore.xyz/p/hilberts-g...

Tomorrow in my Infinity class, we shall discuss the philosophy of ultrafinitism. www.infinitelymore.xyz/t/ultrafinit... #InfinitelyMore

A clip from my conversation with Lex Fridman, in which we discuss who might be the greatest mathematician of all time. The conversation also turns to the question of mathematical style, including my own personal style. www.infinitelymore.xyz/p/on-the-gre... #InfinitelyMore

Announcement on the South Shore Line coming in to Carroll Avenue, Michigan City: "All doors will not open." The train stopped, to let people on and off, and some doors did in fact open. But not all of them.

Ordinary finite Connect Four is a first-player win. How about Infinite Connect Four? Can you describe a winning strategy? What about Infinite Connect Five? Six? Read more on Infinitely More at www.infinitelymore.xyz/p/infinite-c.... #InfinitelyMore #FrivolitiesOfTheGods

Does set theory provide productive guidance like category/model theory? My talk at the Central APA-ASL today will explore this question. Turns out there is a peculiar answer, if one dares to deviate from the familiar story of large cardinals, forcing, and independence...

The slides of my talk here at the ASL/APA meeting in Chicago are now available. jdh.hamkins.org/essential-st...

A deflationary account of Fregean abstraction in set theory.

Tomorrow's lecture for my Infinity class will be on the distinction between actual and potential infinity. open.substack.com/pub/joeldavi... #InfinitelyMore #BookOfInfinity

Coming back to a MathOverflow discussion thread after 16 years. mathoverflow.net/questions/27...

Please enjoy my latest installment in a series of essays on the ordinals—the Cantor Normal Form. An ordinal denotation system, as useful as the decimal number system, but for arbitrary ordinals and grounded in base ω rather than base ten. www.infinitelymore.xyz/p/cantor-nor... #InfinitelyMore

I shall be honored to give the Owens Memorial lecture at Wayne State University in April, joining a distinguished list of previous speakers, including many Fields medalists. "Truth and Paradox in the theory of finite and infinite games." jdh.hamkins.org/truth-and-pa...

Join me next week for the ASL talks at the Central APA Meeting in Chicago, at the elegant Palmer House hotel. www.apaonline.org/mpage/2026ce... ASL Association of Symbolic Logic APA American Philosophical Association

Woo hoo! Ten thousand subscribers on Infinitely More. Growth, however, has not been fully differentiable. www.infinitelymore.xyz #InfinitelyMore

Today's lecture for my Infinity class is on equinumerosity and the notion of size. You are welcome to follow along with the readings for our class. www.infinitelymore.xyz/p/equinumero... #InfinitelyMore #BookOfInfinity

Today's lecture for my infinity class is on The Largest Tweetable Number Follow along on Infinitely More. www.infinitelymore.xyz/p/the-larges... #InfinitelyMore #BookOfInfinity

"Surreal arithmetic is bi-interpretable with set theory" I shall be speaking (in person) at the CUNY Logic Workshop on 13 March. jdh.hamkins.org/surreal-arit...

Can you answer today's quiz in my infinity class? Consider the balls-in-a-sack paradox. You hold an empty sack, with nearby balls numbered 1, 2, 3, and so on. At each step, you will add the next two balls to the sack, and then remove one ball from the sack and discard it.

Today's lecture for my Infinity class is on The paradox of giants. You are kindly welcome to follow along with us in the reading—post your comments, and try the exercise questions! www.infinitelymore.xyz/p/the-parado... #InfinitelyMore #BookOfInfinity

Indecomposable ordinals, those ordinals that cannot be generated from smaller ordinals. www.infinitelymore.xyz/p/indecompos... #InfinitelyMore

Classes will be held in the igloo this week. wsbt.com/news/local/n...

One superpower #math gives me is the ability to picture an interesting object in my head, spark up #Mathematica, and within a few minutes figure out how to make it "real." It's intoxicating! (code in ALT)

Today's lecture for my Infinity class is on the infinite coastline paradox. www.infinitelymore.xyz/p/the-infini... #InfinitelyMore #BookOfInfinity

A while back I had suggested a certain problem in modal graph theory to my Oxford student Wojciech Wołoszyn. He has now solved the problem, with the help of AI. He explains both the result and his AI process on his new substack. woloszyn.substack.com/p/can-ai-wri...

The reverse mathematics of a theorem I proved over 30 years ago is asked on MathOverflow... Regarding infinite time computation. mathoverflow.net/q/507499/1946

Kelly Truelove's AI take on my idea about anthropomorphizing the Russell paradox. open.substack.com/pub/truescip...

Today's quiz in my Infinity class. Consider the Apollonian gasket, obtained by inscribing three congruent circles in a larger circle, and then successively placing the largest possible circles in the regions that remain. en.wikipedia.org/wiki/Apollon...

Today in my Infinity class we discussed supertasks. Feel free to follow along with the readings... www.infinitelymore.xyz/p/supertasks #InfinitelyMore #BookOfInfinity

Ordinal arithmetic. As a part of my series of essays on the surreal numbers, I am making a brief review of ordinal arithmetic. www.infinitelymore.xyz/p/ordinal-ar... #InfinitelyMore

Today's pleasant task: looking over the proposed book covers from the publisher for The Book of Infinity.

An update on China. I have been appointed as Guest Chair Professor at Peking University, with planned visits there during the next 3 summers.

I answered another MathOverflow question, concerning the possibility of a well-ordering on classes (so third-order well-order principle) and the effects on large cardinals. mathoverflow.net/a/507207/1946

I answered a question on MathOverflow about large cardinals in the theory ZFC- without power set. mathoverflow.net/a/507203/1946

The city that never sleeps, it has though pleasantly surprised me #nyc

Join us in my class on Infinity and follow along this semester. This week we'll get into Zeno's paradox, and then the "most-contested equation of middle school," eventually reaching the Riemann rearrangement theorem. open.substack.com/pub/joeldavi... #InfinitelyMore #BookOfInfinity

Todays's topic in my Infinity class. Why not join us and follow along? www.infinitelymore.xyz/p/the-book-o... #InfinitelyMore #BookOfInfinity

Incredible!

The next in my series of essays on ultrafinitism. www.infinitelymore.xyz/p/ultrafinit... #InfinitelyMore

The #edge is the most interesting area …. Not a #knot

hi, political philosopher here! this is not funny, central banks only do this when they're in extreme distress

My new idea for the syllabus next time I teach my core seminar in Philosophy, Science, and Mathematics. Namely, we'll spend a week with: - The two cultures, C. P. Snow - The two cultures of Mathematics, Timothy Gowers - The Hedgehog and the Fox, Isiah Berlin

I shall be giving the Owens Memorial lecture at Wayne State University on April 16. Please join me there. I am honored by the distinguished list of previous speakers... clas.wayne.edu/math/researc...

My paper with Tedy Nenu on Alan Turing and the halting problem has now appeared. doi.org/10.1093/logc...

Here's an old blog post I wrote about a footnote in Turing's 1937 article "On computable numbers with an application to the Entscheidungsproblem," in which he gave a topological argument that any alphabet must be finite. divisbyzero.com/2010/05/27/t...

Anthropomorphizing the Russell paradox, an excerpt from my conversation with @lexfridman.bsky.social. www.infinitelymore.xyz/p/anthropomo... #InfinitelyMore

Oh dear, my offhand remarks in a podcast are now mentioned in the Times of India. share.google/dKF39OIO6yrv...

The Hard Times is a parody punk news website and it is consistently one of the funniest things on the Internet.

Here is a high-quality clickable transcript of my sweeping conversation with @lexfridman on infinity, paradox, philosophy, and mathematics. Nearly four hours of great back and forth. lexfridman.com/joel-david-h...