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67 entries, newest first
  1. notes Boole and the Algebraic Tradition

    How an algebra of classes became a calculus of relations and quantifiers, through Boole, De Morgan, Peirce, and Schröder.

    Series: History of Logic #history-of-logic#mathematical-logic#algebraic-logic#history-of-mathematics#boolean-algebra#relations#quantifiers#interactive-labs
  2. notes Frege, Quantifiers, and Logical Form

    Why variables, scope, and explicit inference changed the representation of mathematical proof, and how Frege's project differed from modern first-order logic.

    Series: History of Logic #history-of-logic#mathematical-logic#formal-language#foundations-of-mathematics#quantifiers#first-order-logic#logicism#higher-order-logic#interactive-labs
  3. notes Rigor, Infinity, and the Axiomatic Method

    How analysis, infinite sets, arithmetic, and alternative geometries changed the questions mathematicians asked about foundations.

    Series: History of Logic #history-of-logic#mathematical-logic#foundations-of-mathematics#set-theory#axiomatization#infinity#real-analysis#non-euclidean-geometry#interactive-labs
  4. notes Paradoxes and Competing Foundations

    Russell's contradiction, Frege's Basic Law V, ramified types, predicativity, and axiomatic set theory as distinct responses to foundational problems.

    Series: History of Logic #history-of-logic#mathematical-logic#foundations-of-mathematics#set-theory#type-theory#logicism#paradoxes#russells-paradox#predicativity#axiomatization#interactive-labs
  5. notes Hilbert's Program and the Study of Proof

    Formalization, finitary reasoning, and the attempt to justify infinitary mathematics through a mathematical analysis of finite derivations.

    Series: History of Logic #history-of-logic#mathematical-logic#proof-theory#consistency#foundations-of-mathematics#hilberts-program#finitism#epsilon-calculus#formalization
  6. notes Intuitionism and Mathematical Construction

    Brouwer, Heyting, constructive evidence, realizability, and the different mathematical programs behind the word constructive.

    Series: History of Logic #history-of-logic#mathematical-logic#constructivism#proof-theory#intuitionistic-logic#realizability#classical-logic
  7. notes Syntax, Truth, and Completeness

    The distinction between derivability and semantic consequence, from formal syntax and Tarski's semantics to Gödel's theorem, Henkin's construction, and nonstandard models.

    Series: History of Logic #history-of-logic#mathematical-logic#semantics#model-theory#completeness#first-order-logic#truth#compactness#lowenheim-skolem
  8. notes Gödel, Rosser, and Incompleteness

    How arithmetic represents proofs, how diagonalization produces an undecidable sentence, and what the two incompleteness theorems establish.

    Series: History of Logic #history-of-logic#mathematical-logic#incompleteness#proof-theory#foundations-of-mathematics#godels-theorems#arithmetic#diagonalization#consistency
  9. notes The Emergence of Computability

    Church, Turing, Kleene, Post, and the mathematical analysis of algorithms, undecidability, relative computation, and Diophantine equations.

    Series: History of Logic #history-of-logic#mathematical-logic#computability#algorithms#turing-machines#undecidability#halting-problem#lambda-calculus#interactive-labs
  10. notes Gentzen and the Structure of Proof

    Natural deduction, sequent calculus, cut elimination, ordinal analysis, and the continuing investigation of the strength and computational content of proofs.

    Series: History of Logic #history-of-logic#mathematical-logic#proof-theory#natural-deduction#consistency#reverse-mathematics#sequent-calculus#cut-elimination#ordinal-analysis#interactive-labs
  11. notes Model Theory Becomes Mathematics

    Definability, quantifier elimination, ultraproducts, nonstandard analysis, and classification as tools for understanding mathematical structures.

    Series: History of Logic #history-of-logic#mathematical-logic#model-theory#semantics#definability#quantifier-elimination#ultraproducts#nonstandard-analysis#stability-theory
  12. notes Set Theory and Independence

    Choice, the continuum hypothesis, Gödel's constructible universe, Cohen's forcing, and the continuing question of which axioms to adopt.

    Series: History of Logic #history-of-logic#mathematical-logic#set-theory#independence#foundations-of-mathematics#forcing#continuum-hypothesis#axiom-of-choice#constructibility
  13. notes Modal Logic: Necessity, Time, Knowledge, and Provability

    How the study of implication developed into a family of logics whose operators express different kinds of necessity.

    Series: History of Logic #history-of-logic#mathematical-logic#modal-logic#semantics#kripke-semantics#temporal-logic#epistemic-logic#provability-logic#interactive-labs
  14. notes Alternative Logics: Truth, Relevance, Inconsistency, and Resources

    Four distinct reasons to reconsider classical inference, illustrated through truth values, relevant implication, inconsistent information, and structural rules.

    Series: History of Logic #history-of-logic#mathematical-logic#nonclassical-logic#proof-theory#linear-logic#many-valued-logic#relevance-logic#paraconsistent-logic#structural-rules
  15. notes Lambda Calculus and the Curry–Howard Correspondence

    How substitution became a theory of computation, and how typed terms came to represent proofs with computational behavior.

    Series: History of Logic #history-of-logic#mathematical-logic#lambda-calculus#type-theory#curry-howard#proof-theory#computation#normalization#interactive-labs
  16. notes Dependent Type Theory: Proofs, Data, and Universes

    How types came to express specifications that depend on values, and why equality, induction, and universe rules became foundational decisions.

    Series: History of Logic #history-of-logic#mathematical-logic#dependent-types#foundations-of-mathematics#proof-assistants#type-theory#identity-types#universes#inductive-types
  17. notes Categorical Logic: Structure, Quantification, and Internal Languages

    How categories provided structural interpretations of proof, function types, quantifiers, and mathematical foundations.

    Series: History of Logic #history-of-logic#mathematical-logic#categorical-logic#semantics#foundations-of-mathematics#category-theory#adjunctions#topos-theory#type-theory
  18. notes Functional Programming and Programming-Language Semantics

    From Lisp and lambda-based language design to mathematical accounts of recursion, polymorphic type inference, and abstraction.

    Series: History of Logic #history-of-logic#mathematical-logic#functional-programming#programming-languages#semantics#lambda-calculus#denotational-semantics#type-inference#domain-theory
  19. notes Automated Theorem Proving: Clauses, Unification, Equality, and Search

    How proof procedures turn a mathematical problem into a search, and why representation, inference rules, and search strategy each matter.

    Series: History of Logic #history-of-logic#mathematical-logic#automated-reasoning#resolution#theorem-proving#unification#equality#proof-search#first-order-logic
  20. notes Complexity, SAT, and SMT

    Why decidable reasoning can be difficult, how conflict-driven solvers exploit structure, and how Boolean search cooperates with mathematical theories.

    Series: History of Logic #history-of-logic#mathematical-logic#complexity#sat#smt#automated-reasoning#np-completeness#dpll#cdcl#decision-procedures#interactive-labs
  21. notes Logic Programming: Clauses as Programs

    How proof search can compute answers, and why a program's logical consequences must be distinguished from the behavior of its execution strategy.

    Series: History of Logic #history-of-logic#mathematical-logic#logic-programming#prolog#automated-reasoning#horn-clauses#sld-resolution#datalog#unification
  22. notes Proof Assistants: Foundations and Trust

    The distinct histories of Automath, LCF, Mizar, inductive provers, dependent-type systems, Metamath, and Lean—and what each architecture asks us to trust.

    Series: History of Logic #history-of-logic#mathematical-logic#proof-assistants#formalization#foundations-of-mathematics#type-theory#trusted-kernel#lean#lcf#coq
  23. notes Program Verification: Invariants, Semantics, and Local Reasoning

    How assertions became a logic of programs, and how proofs of loops, heap operations, compilers, and kernels depend on precise specifications.

    Series: History of Logic #history-of-logic#mathematical-logic#program-verification#hoare-logic#separation-logic#formal-methods#loop-invariants#weakest-preconditions#compiler-correctness
  24. notes Temporal Verification, Model Checking, and Abstraction

    How logics of time became tools for checking ongoing systems, and how symbolic representations and abstraction address the growth of possible behaviors.

    Series: History of Logic #history-of-logic#mathematical-logic#model-checking#temporal-logic#abstract-interpretation#formal-methods#safety-and-liveness#symbolic-verification#abstraction#interactive-labs
  25. notes Formalized Mathematics: Proofs and Reusable Libraries

    How mechanically checked mathematics grew from individual texts and landmark proofs into shared infrastructure for further mathematical work.

    Series: History of Logic #history-of-logic#mathematical-logic#formalized-mathematics#mathematical-libraries#proof-assistants#formalization#proof-reflection#mathlib#lean
  26. notes Homotopy Type Theory and Univalence

    How identity types acquired a geometric interpretation, why equivalence can induce identification, and how cubical theories address computation.

    Series: History of Logic #history-of-logic#mathematical-logic#homotopy-type-theory#univalence#foundations-of-mathematics#type-theory#dependent-types#identity-types#cubical-type-theory
  27. notes Learned Theorem Proving: Search, Formalization, and Discovery

    How statistical guidance works with formal checking, from premise selection to AlphaProof and research formalization, with careful distinctions about evidence and novelty.

    Series: History of Logic #history-of-logic#mathematical-logic#ai#theorem-proving#formalization#automated-reasoning#machine-learning#proof-search#autoformalization
  28. notes Greek and Late-Antique Logic

    Aristotelian demonstration, syllogistic inference, Stoic arguments, and the commentators and translators who shaped their later study.

    Series: History of Logic: Earlier Traditions #history-of-logic#ancient-logic#aristotle#stoicism#history-of-philosophy#syllogistic-logic#propositional-logic#demonstration
  29. notes Arabic, Islamic, and Jewish Logical Traditions

    Translation, demonstration, Avicennan innovations, later teaching traditions, and the movement of logical ideas across Arabic, Hebrew, and Latin.

    Series: History of Logic: Earlier Traditions #history-of-logic#arabic-logic#avicenna#medieval-logic#islamic-philosophy#jewish-philosophy#syllogistic-logic#translation
  30. notes Medieval Latin Logic: Reference, Consequence, and Paradox

    How medieval logicians analyzed the use of terms, the force of logical particles, valid consequences, and self-referential statements.

    Series: History of Logic: Earlier Traditions #history-of-logic#medieval-logic#semantics#paradoxes#supposition-theory#logical-consequence#self-reference#history-of-philosophy
  31. notes Indian Logic: Inference, Evidence, and Analysis

    Nyāya, Buddhist theories of inference, and Navya-Nyāya's technical language, examined through the justification and failure of inferential signs.

    Series: History of Logic: Earlier Traditions #history-of-logic#indian-logic#nyaya#buddhist-logic#epistemology#inference#navya-nyaya#history-of-philosophy
  32. notes Chinese Traditions of Argument: Names, Kinds, and Distinctions

    Mohist standards of reasoning, the School of Names, the white-horse discussion, and Xunzi's account of naming and orderly discourse.

    Series: History of Logic: Earlier Traditions #history-of-logic#chinese-philosophy#mohism#argumentation#philosophy-of-language#analogy#school-of-names#history-of-philosophy
  33. notes Before Boole: Reform, Leibniz, and Bolzano

    Early-modern projects for improving inquiry and calculation, followed by Bolzano's account of propositions, variation, consequence, and explanation.

    Series: History of Logic: Earlier Traditions #history-of-logic#early-modern-logic#leibniz#bolzano#induction#logical-consequence#symbolic-logic#history-of-philosophy
  34. notes Apex Legends: Game Sense

    Notes on the mistakes I keep making in Apex and how I try to stop repeating them. This is only part of game sense, and only the part I have managed to name so far.

    #apex-legends#fps#battle-royale#multiplayer#gaming#guide
  35. notes History of Logic: Series Guide

    Part 0 introduces the series, its reading order, and routes through foundations, computation, formalization, and earlier logical traditions.

    Series: History of Logic #history-of-logic#mathematical-logic#foundations-of-mathematics#formalization#history-of-philosophy#interactive-learning
  36. games Apex Legends

    Everything I have written about Apex Legends, from my settings to notes on how I try to play better.

    competitive current #apex-legends#fps#battle-royale#multiplayer#gaming
  37. notes Why Mathematical Logic Textbooks Look Circular

    Standard textbooks use sets to define first order logic, then define set theory inside first order logic. Where that apparent circularity resolves, and what the metatheory consists of.

    #mathematical-logic#logic#foundations#metamathematics#formalism#lean#textbook#mathematics
  38. notes Apex Legends: Settings and Gear

    The settings, keybinds, sensitivity, and gear I actually play on.

    #apex-legends#fps#battle-royale#multiplayer#settings#sensitivity#gear#gaming
  39. notes I Switched from WordPress to Astro

    Notes from the move off WordPress to a static Astro site, what I gained, and what I gave up.

    #ai#astro#blog#design#migration#site#static-site#web-development#website#milestone
  40. notes How Separation Resolves Russell's Paradox

    Unrestricted comprehension is inconsistent. Separation replaces it, and the relative Russell set is a subset of its base set but never an element of it.

    #mathematical-logic#set-theory#logic#foundations#paradox#proof#mathematics
  41. notes Why Can't You Solve an Equation by Differentiating Both Sides?

    Squaring both sides keeps every original solution, but differentiating does not. The difference comes from the type of the function you apply.

    #algebra#chinese#differential-equation#mathematical-logic#mathematics#proof
  42. notes Can Lorentz Transformations Be Derived from General Relativity?

    How local inertial frames connect Lorentz transformations in special relativity to curved spacetime.

    #differential-geometry#general-relativity#manifold#mathematics#metric-space#physics#special-relativity
  43. notes Why Does Friction Break Time-Reversal Symmetry?

    How microscopic reversibility, probability, and coarse-graining produce macroscopic irreversibility.

    #classical-mechanics#loschmidts-paradox#mathematics#paradox#physics#probability#statistical-mechanics#thermodynamics#time-reversal-symmetry
  44. notes Why Is the Lorentz Transformation Linear?

    A derivation of Lorentz linearity from the structure of inertial frames and spacetime transformations.

    #differential-geometry#linear-algebra#manifold#mathematics#physics#special-relativity
  45. notes Could the Speed of Light Be Variable?

    What the constancy of light speed means, how it is tested, and where variable-speed ideas would have to differ.

    #experimental-physics#mathematics#physics#special-relativity#speed-of-light
  46. notes Why Are So Many Equations of Motion Second Order?

    How first-derivative actions lead to second-order motion, and what Ostrogradsky’s theorem does—and does not—exclude.

    #classical-mechanics#differential-equation#lagrangian-mechanics#mathematics#ostrogradsky-instability#physics
  47. notes Why Are Phasors Used in Circuit Analysis?

    How phasors turn sinusoidal circuit equations into algebra, and what their components represent physically.

    #algebra#circuit-analysis#circuits#differential-equation#electromagnetism#linear-algebra#linear-time-invariant#mathematics#phasor#physics#proof
  48. notes Intro to Generalized Coordinates

    An introduction to generalized coordinates and why they simplify constrained mechanical systems.

    #classical-mechanics#introduction#lagrangian-mechanics#mathematics#physics
  49. notes A Mathematical Exploration of the Virial Theorem

    A derivation and interpretation of the virial theorem through the mathematics of classical mechanics.

    #classical-mechanics#introduction#latex#mathematics#physics
  50. notes Recommendations for Rigorous Classical Mechanics Textbooks

    A reading list for approaching classical mechanics with greater mathematical rigor.

    #classical-mechanics#experience#formalism#guide#mathematics#physics#recommendation#textbook
  51. notes Why Aren't Generalized Coordinates Treated as Functions of Time?

    How partial derivatives of a Lagrangian differ from differentiation along a time-dependent trajectory.

    #classical-mechanics#introduction#lagrangian-mechanics#latex#mathematics#physics
  52. notes A Mathematical Exploration of Norton's Dome and Determinism in Classical Mechanics

    A mathematical look at Norton's dome, non-unique motion, and determinism in classical mechanics.

    #chinese#classical-mechanics#differential-equation#introduction#latex#mathematics#paradox#physics
  53. notes Why Use Squared Error Rather Than Absolute Error?

    A probabilistic and optimization-based explanation of why squared error is so common in loss functions.

    #algebra#computer-science#deep-learning#latex#likelihood#machine-learning#mathematics#optimization#probability#probability-theory#regression-analysis#statistics
  54. notes Intro to Git, GitHub, and VS Code

    A bilingual guide to repositories, forks, clones, branches, commits, and pull requests, with a complete local workflow.

    #chinese#computer-science#git#github#guide#introduction#programming#vscode
  55. notes Diandian: Two Years After the Rescue

    The story of the kitten my family rescued in February 2022, with a 2024 video update.

    #chinese#diandian#experience#family#love#pet#video#memory
  56. notes Constructing Logic Gates from Truth Tables

    Using mathematical logic and Python to reason through a logic-gate construction challenge in Turing Complete.

    #coding#computer-science#gaming#introduction#latex#logic#logic-gate#mathematical-logic#mathematics#programming#python
  57. notes Using a Raspberry Pi to Build a U.S. VPN Server for My Family in China

    A practical record of building a family VPN with Raspberry Pi, SSH, DNS, and Cloudflare.

    #cloudflare#coding#computer-science#ddns#dns#github#great-firewall#linux#network#programming#raspberry-pi#server#software#ssh#video#vpn
  58. notes I Switched from GitHub Pages to WordPress

    Notes from the 2023 move from a Jekyll site on GitHub Pages to WordPress.

    #backend#blog#developer#frontend#github#site#web-development#website#milestone
  59. notes Competitive Mathematics: Factorization

    A structured guide to polynomial factorization, identities, methods, and proofs for mathematical competitions.

    #competition#competitive#guide#latex#mathematical-competition#mathematics#notes
  60. notes A Guide to Preparing for the William Lowell Putnam Mathematical Competition

    Preparation ideas, references, and expectations for the William Lowell Putnam Mathematical Competition.

    #competition#competitive#guide#introduction#latex#mathematical-competition#mathematics
  61. notes Why Must a Linear Subspace Contain the Additive Identity?

    Why nonemptiness and scalar closure force a subspace to contain the ambient zero vector.

    #latex#linear-algebra#mathematics#modern-algebra
  62. notes A Simple Physical Approach to Understanding the Taylor Series

    An intuitive route from motion with changing acceleration to the structure of a Taylor series.

    #guide#mathematics#physics#taylor-series
  63. notes Intro to the Colemak keyboard layout

    A concise introduction to Colemak, its layout choices, and the process of learning it.

    #computer-science#introduction#keyboard-layout#typing
  64. notes My U.S. Visa Interview in Guangzhou, July 2022

    A first-person account of preparing for and completing a U.S. visa interview in Guangzhou.

    #chinese#experience
  65. notes Summation by Parts (Abel Transformation)

    An introduction to summation by parts and its role as the discrete analogue of integration by parts.

    #algebra#chinese#introduction#latex#mathematics
  66. notes Some Advice for New Python Learners

    Practical advice about editors, IDEs, and learning habits for people beginning Python.

    #chinese#experience#guide#ide#programming#python#text-editor
  67. notes A Simple Analogy to Understand Terminal, Shell, TTY, and Console

    A practical mental model for distinguishing terminals, shells, TTYs, and consoles.

    #chinese#computer-science#introduction#linux#operating-system