#categorytheory — Public Fediverse posts

One of the miraculous proofs truly foundational of #categoryTheory - the proof that product (and any other object that is defined using universal property) is unique up to a (unique) isomorphism.

I have to remember to include it in #categorytheoryillustrated

https://proofwiki.org/wiki/Product_%28Category_Theory%29_is_Unique

New paper: "Valuation Without ℝ: A Category-Theoretic Foundation for Finite Measurement"

Can measurement be formalized independently of real numbers AND set theory?

We axiomatize "valuation" as a graded distinguishability map satisfying the ultrametric inequality. Dimension emerges as the growth exponent of the distinguishability graph.

Full paper: https://doi.org/10.5281/zenodo.21795656

#pAdic #QuantumFoundations #CategoryTheory #Measurement

A final monad theory blog post in the current series about transferring nice properties of monads along strong monad morphisms. Today, quotients:

https://stringdiagram.com/2026/08/07/quotients-of-commutative-affine-and-relevant-monads/

#categorytheory

Just a reminder, if you are about to take a category theory course next term/semester.

There is a page of links to reasonably accessible and (legally!) freely downloadable lecture notes etc. at https://logicmatters.net/categories. You could very well find there some helpful preliminary/parallel reading at a level that suits you.

At the gentler end, there are my own notes *Introducing Category Theory*, freely downloadable of course but also available as a minimum cost paperback. Some students do like the book!

If you giving a category theory course, please do alert your students to the links page https://logicmatters.net/categories -- they may well find it useful.

#CategoryTheory

Just learnt that our paper "A study of Kock's fat Delta" (https://arxiv.org/abs/2503.10963) with Nicolai Kraus (@Nicolai_Kraus), Simona Paoli and Stiéphen Pradal (@Stiephen) was accepted for publication in the Journal of Pure and Applied Algebra (JPAA).

I'm quite happy about this, but I'm especially pleased for Stiéphen who's currently working hard to write up his PhD thesis!

#categorytheory

While teaching a course on algebraic theories last semester I mentioned at some point that the familiar bicomplete categories Top and Poset were not algebraic, but were topological. A student asked about this later on and I found that the #Wikipedia page on «topological category» pointed to categories enriched in Top, not categories with a forgetful functor to Set which is topological. While I have lost a lot of faith in Wikipedia recently, I am pleased to report that https://en.wikipedia.org/wiki/Topological_category is now a disambiguation page.

#math #mathematics #topology #algebra #CategoryTheory

Cool writeup presenting universal properties as natural isomorphisms:

https://math.stackexchange.com/questions/3688510/understanding-universal-property-and-universal-element-from-category-theory-in

#categoryTheory

Random #categoryTheory fact: The Yoneda lemma can be seen (among 1000 other things) as a generalization of the definition that a set contains no structure, other than its elements.

Does anybody know how to typeset pullback/pushout corners in typst/fletcher?
The code provided at https://github.com/Jollywatt/typst-fletcher/issues/50#issuecomment-2851846670 does not quite work for me and even when it does, it requires experimenting with degrees which is bad.

[Update] I added my own workaround as a reply to the GitHub issue.

#typst #typesetting #categorytheory

🤦‍♂️ Ah yes, because what every overworked developer dreams of is an IDE that speaks the fluent gibberish of category theory. 🚀 Just sprinkle some "categorical magic dust" on your databases and watch them transform (or maybe just disappear into the void). Call Conexus AI for a personalized headache consultation. 📞🤯
https://categoricaldata.net/ #overworkeddevelopers #categorytheory #IDEs #ConexusAI #techhumor #HackerNews #ngated

📚🤖 "Behold! The magnum opus on #Rust and Category Theory that's sure to revolutionize your understanding of... nothing. 😂 Dive into this unfinished 'draft' if you're into the esoteric joy of turning simple concepts into convoluted gibberish. 🚀👨‍💻✨"
https://hghalebi.github.io/category_theory_transformer_rs/ #CategoryTheory #EsotericHumor #TechHumor #Programming #HackerNews #ngated

Building ML framework with Rust and Category Theory

https://hghalebi.github.io/category_theory_transformer_rs/

#HackerNews #ML #Rust #CategoryTheory #Framework #Development

Towards a Higher-Order Bialgebraic Denotational Semantics by Sergey Goncharov, @[email protected], @[email protected], Henning Urbat, and me has been (unconditionally) accepted at ICFP'26! Abstract below ​:Blobhaj_Read_Octopus:​

#icfp #functionalProgramming #programmingLanguages #semantics #coalgebra #categoryTheory

From 11:00 to 12:00 on Thursday, April 30, the PLUSLE reading group will discuss "Abstract Syntax and Variable Binding" by Marcelo Fiore, Gordon Plotkin, and Daniele Turi.

https://plsl.acp.sdu.dk/posts/2026-04-30-abstract-syntax-and-variable-binding/

#PLUSLE #syntax #programmingLanguages #categoryTheory #lambdaCalculus

Oh joy, another attempt at 'explaining' Category Theory using #orders, because clearly the first thing we all need is more #abstraction in our lives. 🎉 In a groundbreaking revelation, the article tells us orders are about #relationships. 🤯 Who knew binary relations could be so riveting? 🙄
https://abuseofnotation.github.io/category-theory-illustrated/04_order/ #CategoryTheory #HackerNews #HackerNews #ngated

Category Theory Illustrated – Orders

https://abuseofnotation.github.io/category-theory-illustrated/04_order/

#HackerNews #CategoryTheory #Orders #Illustration #Math #Education #Programming

Someone should make one of those "top 10 most satisfying" videos but for #CategoryTheory diagram chasing proofs

In the mountains, I love exploring nature and climbing any little hidden corner.

My academic interests include mathematics (#mathematics) and mathematical logic ( #mathematicallogic #logic), particularly model theory ( #modeltheory), category theory ( #categorytheory), higher-order logic and metalogic ( #metalogic), as well as the philosophy of mathematics and logic ( #philosophyofmathematics #philosophyoflogic), epistemology and ontology of them.

#introduction

Readings shared April 4, 2026. https://jaalonso.github.io/vestigium/posts/2026/04/04-readings_shared_04-04-26 #AI #AI4Math #ATP #Agda #AlphaProof #Autoformalization #CategoryTheory #CoqProver #FunctionalProgramming #ITP #IsabelleHOL #LLMs #LambdaCalculus #LeanProver #Lisp #Logic #LogicProgramming #LLMs #Math #Physics #Programming #Prolog #Racket #RocqProver #Vampire

Propositions As Types Analogy • 1
• https://inquiryintoinquiry.com/2013/01/29/propositions-as-types-analogy-1/

One of my favorite mathematical tricks — it almost seems too tricky to be true — is the Propositions As Types Analogy. And I see hints the 2‑part analogy can be extended to a 3‑part analogy, as follows.

Proof Hint ∶ Proof ∶ Proposition
∷
Untyped Term ∶ Typed Term ∶ Type

or

Proof Hint ∶ Untyped Term
∷
Proof ∶ Typed Term
∷
Proposition ∶ Type

See my working notes on the Propositions As Types Analogy —
• https://oeis.org/wiki/Propositions_As_Types_Analogy

#Mathematics #CategoryTheory #ProofTheory #TypeTheory
#Logic #Analogy #Isomorphism #PropositionalCalculus
#CombinatorCalculus #CombinatoryLogic #LambdaCalculus
#Peirce #LogicalGraphs #GraphTheory #RelationTheory

Survey of Precursors Of Category Theory • 6
• https://inquiryintoinquiry.com/2025/05/05/survey-of-precursors-of-category-theory-6/

A few years ago I began a sketch on the “Precursors of Category Theory”, tracing the continuities of the category concept from Aristotle, to Kant and Peirce, through Hilbert and Ackermann, to contemporary mathematical practice. A Survey of resources on the topic is given below, still very rough and incomplete, but perhaps a few will find it of use.

Background —

Precursors Of Category Theory
• https://oeis.org/wiki/Precursors_Of_Category_Theory

Propositions As Types Analogy
• https://oeis.org/wiki/Propositions_As_Types_Analogy

Blog Series —

Notes On Categories
• https://inquiryintoinquiry.com/2013/02/22/notes-on-categories-1/

Precursors Of Category Theory
1. https://inquiryintoinquiry.com/2024/05/25/precursors-of-category-theory-1-a/
2. https://inquiryintoinquiry.com/2024/05/26/precursors-of-category-theory-2-a/
3. https://inquiryintoinquiry.com/2024/05/27/precursors-of-category-theory-3-a/
4. https://inquiryintoinquiry.com/2024/05/28/precursors-of-category-theory-4-a/
5. https://inquiryintoinquiry.com/2024/05/29/precursors-of-category-theory-5-a/
6. https://inquiryintoinquiry.com/2024/05/30/precursors-of-category-theory-6-a/

Precursors Of Category Theory • Discussion
1. https://inquiryintoinquiry.com/2020/09/13/precursors-of-category-theory-discussion-1/
2. https://inquiryintoinquiry.com/2020/09/21/precursors-of-category-theory-discussion-2/
3. https://inquiryintoinquiry.com/2020/09/25/precursors-of-category-theory-discussion-3/

Categories à la Peirce —

C.S. Peirce • A Guess at the Riddle
• https://inquiryintoinquiry.com/2012/03/21/c-s-peirce-a-guess-at-the-riddle/

Peirce's Categories
1. https://inquiryintoinquiry.com/2015/10/30/peirces-categories-1/
2. https://inquiryintoinquiry.com/2015/10/31/peirces-categories-2/
3. https://inquiryintoinquiry.com/2015/11/04/peirces-categories-3/
•••
19. https://inquiryintoinquiry.com/2020/05/13/peirces-categories-19/
20. https://inquiryintoinquiry.com/2020/05/14/peirces-categories-20/
21. https://inquiryintoinquiry.com/2020/06/25/peirces-categories-21/

C.S. Peirce and Category Theory
1. https://inquiryintoinquiry.com/2021/06/23/c-s-peirce-and-category-theory-1/
2. https://inquiryintoinquiry.com/2021/06/24/c-s-peirce-and-category-theory-2/
3. https://inquiryintoinquiry.com/2021/06/27/c-s-peirce-and-category-theory-3/
4. https://inquiryintoinquiry.com/2021/06/28/c-s-peirce-and-category-theory-4/
5. https://inquiryintoinquiry.com/2021/06/29/c-s-peirce-and-category-theory-5/
6. https://inquiryintoinquiry.com/2021/06/30/c-s-peirce-and-category-theory-6/
7. https://inquiryintoinquiry.com/2021/07/01/c-s-peirce-and-category-theory-7/
8. https://inquiryintoinquiry.com/2021/07/02/c-s-peirce-and-category-theory-8/

#Aristotle #Peirce #Kant #Carnap #Hilbert #Ackermann #SaundersMacLane
#Abstraction #Analogy #CategoryTheory #FunctionalLogic #RelationTheory
#PrecursorsOfCategoryTheory #PropositionsAsTypes #Semiotics #TypeTheory

Tomorrow's mathober is "faithful"

I am stumped at the moment on how to play with faithful functors - any suggestions are welcome.

#categoryTheory #mathober #functors

Tomorrow's mathober is "faithful"

I am stumped at the moment on how to play with faithful functors - any suggestions are welcome.

#categoryTheory #mathober #functors

Tomorrow's mathober is "faithful"

I am stumped at the moment on how to play with faithful functors - any suggestions are welcome.

#categoryTheory #mathober #functors

Tomorrow's mathober is "faithful"

I am stumped at the moment on how to play with faithful functors - any suggestions are welcome.

#categoryTheory #mathober #functors

Tomorrow's mathober is "faithful"

I am stumped at the moment on how to play with faithful functors - any suggestions are welcome.

#categoryTheory #mathober #functors

📚🤓 Oh, look! Another mind-numbing dive into the abstract abyss of Category Theory, where somehow "natural transformations" sound like something out of a biology textbook. But fear not, if you squint hard enough, you might just see a functor magically morph into something more... or not. 🙃🔄
https://abuseofnotation.github.io/category-theory-illustrated/11_natural_transformations/ #CategoryTheory #AbstractMath #Functors #NaturalTransformations #MathHumor #HackerNews #ngated

📚🤓 Oh, look! Another mind-numbing dive into the abstract abyss of Category Theory, where somehow "natural transformations" sound like something out of a biology textbook. But fear not, if you squint hard enough, you might just see a functor magically morph into something more... or not. 🙃🔄
https://abuseofnotation.github.io/category-theory-illustrated/11_natural_transformations/ #CategoryTheory #AbstractMath #Functors #NaturalTransformations #MathHumor #HackerNews #ngated

📚🤓 Oh, look! Another mind-numbing dive into the abstract abyss of Category Theory, where somehow "natural transformations" sound like something out of a biology textbook. But fear not, if you squint hard enough, you might just see a functor magically morph into something more... or not. 🙃🔄
https://abuseofnotation.github.io/category-theory-illustrated/11_natural_transformations/ #CategoryTheory #AbstractMath #Functors #NaturalTransformations #MathHumor #HackerNews #ngated

📚🤓 Oh, look! Another mind-numbing dive into the abstract abyss of Category Theory, where somehow "natural transformations" sound like something out of a biology textbook. But fear not, if you squint hard enough, you might just see a functor magically morph into something more... or not. 🙃🔄
https://abuseofnotation.github.io/category-theory-illustrated/11_natural_transformations/ #CategoryTheory #AbstractMath #Functors #NaturalTransformations #MathHumor #HackerNews #ngated

Readings shared April 3, 2025. https://jaalonso.github.io/vestigium/posts/2025/04/03-readings_shared_04-03-25 #AI #AlphaProof #CategoryTheory #FunctionalProgramming #Haskell #ITP #IsabelleHOL #LLMs #LeanProver #Math

Readings shared August 20, 2024. https://jaalonso.github.io/vestigium/posts/2024/08/21-readings_shared_08-20-24 #ITP #Lean4 #Coq #ACL2 #AlphaProof #Math #Haskell #FunctionalProgramming #Logic #Math #CategoryTheory #TypeTheory

Peirce's 1885 “Algebra of Logic” • Discussion 2
• https://inquiryintoinquiry.com/2024/04/03/peirces-1885-algebra-of-logic-discussion-2/

Re: FB | Daniel Everett

One thing I've been trying to understand for a very long time is the changes in Peirce's writing about math and logic from 1865 to 1885. If there's anything I've learned from reading Peirce in the often dim light of intellectual history it is to be wary of progressivist assumptions — but unlike many of his other fans I apply that caution also within the body of his own work. Long story short, from 1865 to 1885 I see progress on several fronts but also bits of backsliding from his more prescient early insights. So it's a puzzle … and it will take more study to ravel out the reasons why.

Resources for reconciling Peirce's two accounts —
1. The 1870 account of logical involution
2. The 1885 account of universal quantification

Peirce's 1870 “Logic of Relatives” • Selection 12 • The Sign of Involution
• https://inquiryintoinquiry.com/2014/06/09/peirces-1870-logic-of-relatives-selection-12/
Comments —
(1) https://inquiryintoinquiry.com/2014/06/10/peirces-1870-logic-of-relatives-comment-12-1/
(2) https://inquiryintoinquiry.com/2014/06/11/peirces-1870-logic-of-relatives-comment-12-2/
(3) https://inquiryintoinquiry.com/2014/06/12/peirces-1870-logic-of-relatives-comment-12-3/
(4) https://inquiryintoinquiry.com/2014/06/14/peirces-1870-logic-of-relatives-comment-12-4/
(5) https://inquiryintoinquiry.com/2014/06/15/peirces-1870-logic-of-relatives-comment-12-5/

Peirce's 1885 “Algebra of Logic” • Selections
(1) https://inquiryintoinquiry.com/2024/03/24/peirces-1885-algebra-of-logic-selection-1/
(2) https://inquiryintoinquiry.com/2024/03/26/peirces-1885-algebra-of-logic-selection-2/
(3) https://inquiryintoinquiry.com/2024/03/30/peirces-1885-algebra-of-logic-selection-3/
(4) https://inquiryintoinquiry.com/2024/04/01/peirces-1885-algebra-of-logic-selection-4/

Peirce, C.S. (1885), “On the Algebra of Logic : A Contribution to the Philosophy of Notation”, American Journal of Mathematics 7, 180–202.
• https://www.jstor.org/stable/2369451

#Peirce #Logic #AlgebraOfLogic #LogicOfRelatives #RelationTheory #CategoryTheory
#Semiotics #PredicateCalculus #Quantification #LogicalInvolution #ComputerScience

Peirce's 1885 “Algebra of Logic” • Discussion 1
• https://inquiryintoinquiry.com/2024/04/02/peirces-1885-algebra-of-logic-discussion-1/

Re: FB | Daniel Everett

DE:
❝One of the most important papers in the history of logic. “On the Algebra of Logic” was the first to introduce the term “quantifier”.

❝Peirce, C.S. (1885), “On the Algebra of Logic : A Contribution to the Philosophy of Notation”, American Journal of Mathematics 7, 180–202.
• https://www.jstor.org/stable/2369451 ❞

As far as quantification by any other word goes, Peirce had already introduced a more advanced and “functional” concept of quantification in his 1870 “Logic of Relatives”. The subsequent passage to Fregean styles of first order logic would turn out to be a retrograde movement toward syntacticism (a species of nominalism), as seen in the general run of what fol‑lowed in the fol‑lowing years.

See ☞ Peirce's 1870 “Logic of Relatives”
• https://inquiryintoinquiry.com/2019/09/24/peirces-1870-logic-of-relatives-overview/

Especially ☞ “The Sign of Involution”
• https://inquiryintoinquiry.com/2014/06/09/peirces-1870-logic-of-relatives-selection-12/

The connection between logical involution and universal quantification which Peirce put to use in his 1870 Logic of Relatives will turn up again a century later with the application of category theory to computer science and both of those in turn to logic. Just one more time Peirce was that far ahead of it.

See ☞ Lambek and Scott (1986), Introduction to Higher Order Categorical Logic, Cambridge University Press.
• https://oeis.org/wiki/User:Jon_Awbrey/Prospects_for_Inquiry_Driven_Systems#Lambek

#Peirce #Logic #AlgebraOfLogic #LogicOfRelatives #RelationTheory #CategoryTheory
#Semiotics #PredicateCalculus #Quantification #LogicalInvolution #ComputerScience

As I prepare to head back home from #Cambridge, I'm reflecting on how much I've learned and on the hospitality shown to me by Jamie Vicary and his graduate students, @jonmsterling, and the computer lab as a whole. My first trip to the UK has been the experience of a lifetime and I look forward to seeing new friends I've made here again soon.

I was surprised to find that one person did a great deal to make me feel welcome despite the fact that I never met her. I noticed the pictured pride flag on my first day in the computer lab, and I assumed everyone signed it as part of some event. I don't talk much about being queer on Mastodon, but seeing this definitely helped me feel much more at ease in a place which was foreign to me, an American mathematician, in multiple senses.

(1/2)

#ComputerScience #CategoryTheory #AppliedCategoryTheory #queer

My talk from yesterday on a categorical semantics for neural nets for the New York Category Theory Seminar has already been posted on YouTube! You can find it at https://www.youtube.com/watch?v=FKkpVKuspmA and you can see more about this seminar at https://www.sci.brooklyn.cuny.edu/~noson/Seminar/. The preprint I mention is https://arxiv.org/abs/2308.00677 and the talk by Joyal which was mentioned at the end can be found at https://www.youtube.com/watch?v=MxClaWFiGKw.

#CategoryTheory #AppliedCategoryTheory #AI #MachineLearning #ComputerScience #UniversalAlgebra #NeuralNets

In a couple hours I'll be giving a talk online for the New York Category Theory Seminar! This is going to be another iteration of "A categorical semantics for neural networks", which I first discussed last week at the Cambridge Logic and Semantics Seminar. I got some really helpful questions/feedback last week, so I'll have some new thoughts to share today.

In particular, I think I may want to use a horizontal categorification of clones, rather than traditional multicategories.

More info:
https://www.sci.brooklyn.cuny.edu/~noson/Seminar/

#AppliedCategoryTheory #CategoryTheory #NeuralNets #AI #MachineLearning #ComputerScience

I will be giving a talk on a functorial semantics for neural nets on Friday at the #Cambridge computer lab's Logic and Semantics Seminar. If you happen to be in the area at the time, consider checking it out!

This will be my first talk on a synthesis of my paper on discrete neural nets (https://arxiv.org/abs/2308.00677) and the categorified invariant theory appearing in my thesis (https://aten.cool/documents/thesis.pdf).

Abstract and other info: https://www.cst.cam.ac.uk/seminars/list/208831

#CategoryTheory #AppliedCategoryTheory #AI #MachineLearning #ComputerScience #logic #math #combinatorics #UniversalAlgebra

Good morning UK! In two weeks I'll be visiting #Cambridge for about two weeks. Please let me know if there's anything cool I should check out while I'm there.

I'll be speaking at this seminar (https://talks.cam.ac.uk/show/index/6375) about a functorial semantics for neural nets. I still need to send in an abstract, so my talk isn't listed yet. This topic is a synthesis of my preprint «Discrete neural nets and polymorphic learning» (https://arxiv.org/abs/2308.00677) as well as some of the results from my thesis (https://aten.cool/documents/thesis.pdf).

I am planning on making a trip to #Nottingham at some point, as well.

#AI #MachineLearning #AppliedCategoryTheory #Combinatorics #CategoryTheory

I'm giving another talk on discrete neural nets and polymorphic learning at the #CUBoulder PALS seminar (https://math.colorado.edu/algebralogic) at 230pm MDT today! You can find the preprint I'm discussing at https://arxiv.org/abs/2308.00677. As usual, a recording will be available in case you'd like to watch later.

#AI #CategoryTheory #algebra #AbstractAlgebra #Combinatorics #ComputerScience #AppliedCategoryTheory

Love to see #AppliedCategoryTheory in the Linux space:

#Linux API for Software Disagnostics
Accelerated with #CategoryTheory in View
by Dmitry Vostokov
https://www.patterndiagnostics.com/accelerated-linux-api-book

Peirce's 1870 “Logic of Relatives” • Selection 3.2
• https://inquiryintoinquiry.com/2014/01/30/peirces-1870-logic-of-relatives-selection-3/

❝§3. Application of the Algebraic Signs to Logic❞

❝The Signs of Inclusion, Equality, Etc.❞

❝But not only do the significations of \(=\) and \(<\) here adopted fulfill all absolute requirements, but they have the supererogatory virtue of being very nearly the same as the common significations. Equality is, in fact, nothing but the identity of two numbers; numbers that are equal are those which are predicable of the same collections, just as terms that are identical are those which are predicable of the same classes.

❝So, to write \(5 < 7\) is to say that \(5\) is part of \(7,\) just as to write \(\mathrm{f} < \mathrm{m}\) is to say that Frenchmen are part of men. Indeed, if \(\mathrm{f} < \mathrm{m},\) then the number of Frenchmen is less than the number of men, and if \(\mathrm{v} = \mathrm{p},\) then the number of Vice-Presidents is equal to the number of Presidents of the Senate; so that the numbers may always be substituted for the terms themselves, in case no signs of operation occur in the equations or inequalities.❞

(Peirce, CP 3.66)

#Peirce #Logic #LogicOfRelatives #RelationTheory #LOR1870
#Boole #LogicalCalculus #MathematicalLogic #LogicalGraphs
#PropositionalCalculus #PredicateCalculus #CategoryTheory

Peirce's 1870 “Logic of Relatives” • Selection 2.1
• https://inquiryintoinquiry.com/2014/01/29/peirces-1870-logic-of-relatives-selection-2/

❝§3. Application of the Algebraic Signs to Logic❞

❝Numbers Corresponding to Letters❞

❝I propose to use the term “universe” to denote that class of individuals about which alone the whole discourse is understood to run. The universe, therefore, in this sense, as in Mr. De Morgan's, is different on different occasions. In this sense, moreover, discourse may run upon something which is not a subjective part of the universe; for instance, upon the qualities or collections of the individuals it contains.

❝I propose to assign to all logical terms, numbers; to an absolute term, the number of individuals it denotes; to a relative term, the average number of things so related to one individual. Thus in a universe of perfect men \((\mathrm{men}),\) the number of “tooth of” would be 32. The number of a relative with two correlates would be the average number of things so related to a pair of individuals; and so on for relatives of higher numbers of correlates. I propose to denote the number of a logical term by enclosing the term in square brackets, thus, \([t].\)❞

#Peirce #Logic #LogicOfRelatives #RelationTheory #LOR1870
#Boole #LogicalCalculus #MathematicalLogic #LogicalGraphs
#PropositionalCalculus #PredicateCalculus #CategoryTheory

Peirce's 1870 “Logic of Relatives” • Selection 1.2
• https://inquiryintoinquiry.com/2014/01/27/peirces-1870-logic-of-relatives-selection-1/

❝The conjugative term involves the conception of third, the relative that of second or other, the absolute term simply considers an object. No fourth class of terms exists involving the conception of fourth, because when that of third is introduced, since it involves the conception of bringing objects into relation, all higher numbers are given at once, inasmuch as the conception of bringing objects into relation is independent of the number of members of the relationship. Whether this reason for the fact that there is no fourth class of terms fundamentally different from the third is satisfactory of not, the fact itself is made perfectly evident by the study of the logic of relatives.❞

One thing that strikes me about the above passage is a pattern of argument I can recognize as invoking a closure principle. This is a figure of reasoning Peirce uses in three other places: his discussion of continuous predicates, his definition of a sign relation, and his formulation of the pragmatic maxim itself.

One might also call attention to the following two statements:

❝Now logical terms are of three grand classes.❞

❝No fourth class of terms exists involving the conception of fourth, because when that of third is introduced, since it involves the conception of bringing objects into relation, all higher numbers are given at once, inasmuch as the conception of bringing objects into relation is independent of the number of members of the relationship.❞

#Peirce #Logic #LogicOfRelatives #RelationTheory #LOR1870
#Boole #LogicalCalculus #MathematicalLogic #LogicalGraphs
#PropositionalCalculus #PredicateCalculus #CategoryTheory

Peirce's 1870 “Logic of Relatives” • Selection 1.1
• https://inquiryintoinquiry.com/2014/01/27/peirces-1870-logic-of-relatives-selection-1/

We pick up Peirce's text at the following point.

❝§3. Application of the Algebraic Signs to Logic❞

❝Use of the Letters❞

❝The letters of the alphabet will denote logical signs.

❝Now logical terms are of three grand classes.

❝The first embraces those whose logical form involves only the conception of quality, and which therefore represent a thing simply as “a ──”. These discriminate objects in the most rudimentary way, which does not involve any consciousness of discrimination. They regard an object as it is in itself as such (quale); for example, as horse, tree, or man. These are absolute terms.

❝The second class embraces terms whose logical form involves the conception of relation, and which require the addition of another term to complete the denotation. These discriminate objects with a distinct consciousness of discrimination. They regard an object as over against another, that is as relative; as father of, lover of, or servant of. These are simple relative terms.

❝The third class embraces terms whose logical form involves the conception of bringing things into relation, and which require the addition of more than one term to complete the denotation. They discriminate not only with consciousness of discrimination, but with consciousness of its origin. They regard an object as medium or third between two others, that is as conjugative; as giver of ── to ──, or buyer of ── for ── from ──. These may be termed conjugative terms.❞

#Peirce #Logic #LogicOfRelatives #RelationTheory #LOR1870
#Boole #LogicalCalculus #MathematicalLogic #LogicalGraphs
#PropositionalCalculus #PredicateCalculus #CategoryTheory

Peirce's 1870 “Logic of Relatives” • Preliminaries 5
• https://inquiryintoinquiry.com/2014/01/27/peirces-1870-logic-of-relatives-preliminaries/

Individual terms are taken to denote individual entities falling under a general term. Peirce uses upper case Roman letters for individual terms, for example, the individual horses \(\mathrm{H}, \mathrm{H}^{\prime}, \mathrm{H}^{\prime\prime}\) falling under the general term \(\mathrm{h}\) for horse.

The path to understanding Peirce's system and its wider implications for logic can be smoothed by paraphrasing his notations in a variety of contemporary mathematical formalisms, while preserving the semantics as much as possible. Remaining faithful to Peirce's orthography while adding parallel sets of stylistic conventions will, however, demand close attention to typography-in-context.

Current style sheets for mathematical texts specify italics for mathematical variables, with upper case letters for sets and lower case letters for individuals. So we need to keep an eye out for the difference between the individual \(\mathrm{X}\) of the genus \(\mathrm{x}\) and the element \(x\) of the set \(X\) as we pass between the two styles of text.

#Peirce #Logic #LogicOfRelatives #RelationTheory #LOR1870
#Boole #LogicalCalculus #MathematicalLogic #LogicalGraphs
#PropositionalCalculus #PredicateCalculus #CategoryTheory

Peirce's 1870 “Logic of Relatives” • Preliminaries 4
• https://inquiryintoinquiry.com/2014/01/27/peirces-1870-logic-of-relatives-preliminaries/

Conjugative Terms (Higher Adic Relatives)
• https://inquiryintoinquiry.files.wordpress.com/2021/11/peirces-1870-lor-e280a2-conjugative-terms-higher-adic-relatives-2.0.png

The Table displays the single-letter abbreviations and their verbal equivalents for the “conjugative terms” (or “higher adic relative terms”) used in Peirce's examples of logical formulas. Peirce used a distinctive typeface for the abbreviations of higher adic relative terms, rendered here as LaTeX “mathfrak”, Fraktur, or Gothic.

#Peirce #Logic #LogicOfRelatives #RelationTheory #LOR1870
#Boole #LogicalCalculus #MathematicalLogic #LogicalGraphs
#PropositionalCalculus #PredicateCalculus #CategoryTheory

This looks like a really nice, visual, first intro to concepts related to #categorytheory.

https://abuseofnotation.github.io/category-theory-illustrated/

#sets, #categories, #monoids, #orders, #logic, #functors

Credits: @abuseofnotation

This looks like a really nice, visual, first intro to concepts related to #categorytheory.

https://abuseofnotation.github.io/category-theory-illustrated/

#sets, #categories, #monoids, #orders, #logic, #functors

Credits: @abuseofnotation

This looks like a really nice, visual, first intro to concepts related to #categorytheory.

https://abuseofnotation.github.io/category-theory-illustrated/

#sets, #categories, #monoids, #orders, #logic, #functors

Credits: @abuseofnotation