Logic Matters

Elisabeth Brauss played Mozart's 23rd Piano Concerto at the Cartagena Festival de Música ten days ago.A terrific performance she evidently much enjoyed.

www.youtube.com/watch?v=rX5c...

This tells you a lot more about LW than about his vary various Cambridge contemporaries.

There's a new version of my *Introducing Category Theory* now available -- a freely downloadable PDF and also a very-cheap-for-its-size pbk. Enough corrections/improvements to count as a "third edition". For info/link see logicmatters.net/categories

Please spread the word! #MathSky #PhilSky

The second issue of the new Journal for the Philosophy of Mathematics is now online (open access). Includes five pieces on sets and pluralities which (on a quick browse) seem interesting and good. Take a look! #MathSky #PhilSky riviste.fupress.net/index.php/jpm

Today’s epiphany… here the adoration of the magi by Fra Angelico & Fra Filippo Lippi 1440-60. National gallery of art Washington DC.

A new blog post about using AI in proofreading the upcoming revised 2nd edition of my category theory book. Might be of interest to other maths writers. www.logicmatters.net/2025/12/28/a...

#MathSky

Oddly the video has disappeared. I do hope not because Elisabeth was herself unhappy with her performance which her audience obviously loved.

There will be a revised version of my category theory book in January. Mostly minor changes for reader-friendliness. But I have expanded the short chapter on ETCS at the very end of the book into two short chapters. Here's a draft: www.logicmatters.net/resources/pd... Comments very welcome! #MathSky

YouTube video by Wigmore Hall Elisabeth Brauss | Beethoven, Grieg, Hans Abrahamsen and Liszt - Live from Wigmore Hall

Wonderful concert by Elisabeth Brauss at Wigmore Hall on Tuesday. Her Beethoven Op. 110 particularly moving -- www.youtube.com/watch?v=Puyd...

Paul Klee
The Bounds of the Intellect, 1927

It is out: it is amazing.

The Philosophy Blogosphere in 2025 - Daily Nous What philosophy blogs are active in 2025? Below is a list of philosophy blogs and blog-newsletters, mostly limited to ones that have been updated at least once in the past month. I'm sure I've missed some. And some active blogs may have been on a brief hiatus and so unfairly excluded by the "one month"

Daily Nous has a nice list of currently active philosophy blogs at dailynous.com/2025/09/18/t... It doesn't mention Logic Matters, but it staggers on into its twentieth year, still with occasional logic and phil maths content, at www.logicmatters.net/blog

CD cover ...black and white photo of Lea and Thomas

New double CD of Lea Desandre and Thomas Dunford (and the Jupiter Ensemble) performing Dowland and Purcell. Absolutely superb playing and often extraordinarily moving. (Had the good fortune to see them live at Wigmore Hall last week -- just stunning.)

Cover of forthcoming CD by the Pavel Haas Quartet

CD Forthcoming soon! Love the cover photo :)

Poetic serendipity - Logic Matters I have written before about the pleasure of serendipitous finds in charity second-hand bookshops. It isn’t the matter of saving a few pounds (or of giving the money to a charity rather than a chain bo...

Yes! I agree! -- and Van Gogh particularly admired it too. www.logicmatters.net/2025/07/12/p...

First 5 star Amazon rating AND first typo report for new edition of *Introducing Category Theory*. Ah well ...

Poetic serendipity - Logic Matters I have written before about the pleasure of serendipitous finds in charity second-hand bookshops. It isn’t the matter of saving a few pounds (or of giving the money to a charity rather than a chain bo...

New blog post ... on Van Gogh, Deryn Rees-Jones (@notjustdancing.bsky.social), Proust, Clive James: www.logicmatters.net/2025/07/12/p...

I've updated my page of links to entry-level lecture notes and online books on category theory.

The page is visited a lot (3K times a month) so I ought to try to keep it in good shape. So any additions/corrections will be really welcome!

www.logicmatters.net/categories/

#mathsky #philsky

The gently-paced notes aim to be pretty accessible even if you have a relatively modest mathematical background. Could be useful prelim reading if you are taking an industrial strength course next term/semester. Or if you just want to get to know something about what the categorial fuss is about!

Part of cover ... author/title in white on red background

ICYMI At last, there is a pbk version of my notes *Introducing Category Theory*, 2nd edn., ISBN 1068346701. Amazon-only print on demand to keep the price minimal for a 500pp book. Or you can still download the PDF from logicmatters.net. Spread the word :)

#mathsky #philsky

Part of cover image, author/title in white on red background

Sound the trumpets ... At last, at last, there is a pbk version of my notes *Introducing Category Theory*, 2nd edn., ISBN 1068346701. Amazon-only print on demand to keep the price minimal for a 500pp book. Or you can still download the PDF from logicmatters.net. Spread the word :)

They were simply amazing! And with their new violist have they ever sounded better?

But that’s surely not a “trick” … it’s just applying about the most fundamental fact about triangles twice ….

Oops sorry I missed your earlier post!

It’s quite trivial. No pythagoras or Cartesian coordinates needed.

Move top apex to bottom right of big square, and area stays the same (why?). Now move bottom apex to bottom right of middle square, and area still stays the same. But you’ve ended up with triangle half the middle square so area 10.

The linked piece by Keith Frankish on what LLMs are doing is (characteristically) excellent.

Simply wonderful Schubert playing from Elisabeth Brauß

www.bbc.co.uk/sounds/play/... From about 18 mins into the programme (available for about a month).

Excerpt from book cover, white author name/title on red background

You can now download a complete version of *Introducing Category Theory* from www.logicmatters.net/categories. Just needs final proofreading.

Has it any virtues? Well, at least it might distract you for a while, as the world goes to hell in a handcart ...

#mathsky #philsky

Katherine Rundell · Consider the Hare ‘The cat of the wood,’ Heaney calls them. ‘The stag of the cabbages.’ If there is magic in this world, some part...

‘The Easter bunny was a hare long before he was a rabbit; the hare was sacred to Eostre, the Saxon goddess of spring – no rabidly cute bundle of fluff.’

Katherine Rundell considers the hare: www.lrb.co.uk/the-paper/v4...

YouTube video by Elisabeth Brauß Elisabeth Brauß: Beethoven - Piano Concerto No.4 (Mvt. 3)

Elisabeth Brauß playing the last movement of Beethoven's 4th Piano Concerto. Joyous!

www.youtube.com/watch?v=OJX0...