Logic Matters

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...

Here are links to a dozen blog posts "Schubert on Sunday", linking mostly to some wonderfully good YouTube videos. You might well have missed some -- take a quick look!

#Schubert

www.logicmatters.net/tag/schubert...

BW photo of Charlotte Saluste-Bridoux and Joseph Havlat from their recording session

There's a terrific new Schubert CD by Charlotte Saluste-Bridoux and her piano duo partner Joseph Havlat.

www.delphianrecords.com/products/sch...

Here's a link to their playing the Fantasia D. 934 at Wigmore Hall (and some other Schubert links too). Enjoy!

www.logicmatters.net/tag/schubert...

Arnie Koslow used to say that the talk of “scaffolding” that we supposedly find e.g. in Hilbert is a mistranslation… and the reference was to the wooden frames of old houses (not temporary at all!).

@classicalmusic
Wolfgang Amadeus Mozart - 12 Variationen über "Ah, vous dirai-je Maman" für Klavier C-Dur, KV 265

Elisabeth Brauß, Klavier

https://www.youtube.com/watch?v=3d7L14O9BOY

#music #classic #piano

Patricia Kopatchinskaja plays Schubert’s «Trout Quintet» - Gstaad Digital Festival

Schubert on Sunday. A quite terrific performance of the Trout Quintet.

www.gstaaddigitalfestival.ch/en/video/pat...

(You may have to sign up to the Gstaad site, but that's free.)

Portion of book cover

I lied. I said "apart from proof reading for typos and thinkos, this [posted yesterday] is the version which will be paperbacked". But today there's a new version of *Introducing Category Theory* with improved last chapter. And so it goes.

www.logicmatters.net/categories/

#mathsky #philsky

Part of book cover: white author/title names on red background

There's a new complete version of *Introducing Category Theory* downloadable at logicmatters.net/categories

Apart from proof reading for typos and thinkos, this is the version which will be paperbacked (as cheaply as possible) in May. So let me know of any errors, however small!

#mathsky #philsky

My good friend, the logician Thomas Forster, tells me that he once shared an office with Giovanna Corsi, who at one point shared an office with Jean van Heijenoort, who was Trotsky's personal secretary in the 1930s ....  Just four handshakes from Trotsky.

Could provide a good warm-up if you are about to take an industrial-strength category theory course ... or you could dip in just if you want an entry-level intro. (I make no claims for these notes other than that some people do find them very accessible.)

Parts I and II cover similar ideas to Leinster's book, but slower, with more chat. Part III peeks over the fence at the idea of an elementary topos, at roughly Goldblatt's level in his opening chapters.

This is the second edition, with material differently arranged from the first edition, and quite a lot of additions and improvements.

Part of book cover, giving title in white on red background

Belatedly (real life happens ...), there's a complete version of my *Introducing Category Theory*. A month's tinkering now, and there should be a cheap pbk. But you can download a draft for free from www.logicmatters.net/categories

#mathsky #philsky

YouTube video by Gilmore Piano Festival Elisabeth Brauss | 2024 - 2025 Rising Stars Series

Elisabeth Brauss concert a week ago … Bach, Beethoven, Hough, Schumann, Prokofiev. Wonderful performances very engagingly filmed. m.youtube.com/watch?v=4gqb...

YouTube video by Gilmore Piano Festival Elisabeth Brauss | 2024 - 2025 Rising Stars Series

Here is Elisabeth in the same programme … m.youtube.com/watch?v=4gqb...