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Deniz Sarikaya, Thorsten Altenkirch

aboutlogic

A Mathematics , Science and Society & Culture podcast

#1 in Mathematics · 🇿🇦 #2 in Mathematics · 🇸🇬
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About the show

aboutlogic is a podcast on logic, foundations of mathematics, philosophy, and theoretical computer science. aboutlogic features in-depth conversations with people working in and around the foundations of these subjects. We talk about topics ranging from the foundations of computer science and set theory to critical thinking, puzzles, and what academic life is really like—its motivations, frustrations, and surprises.

Newest episodes

aboutlogic: premises #11 | Category Theory: Algebra on Steroids?

29 min

Category Theory: Algebra on Steroids? | aboutlogic: premises #11 Is category theory just algebra on steroids? In this premises, Thorsten and Deniz give a pedestrian-speed introduction to category theory: structural mathematics, universal properties, duality and why products always come with coproducts, co-natural numbers, diagram chasing, and why homotopy type theory leads straight to higher categories. They also ask how category theory and type theory fit together and why Thorsten sees category theory as a way to structure ideas rather than the source of them.

aboutlogic #24 | Why Didn't Homotopy Type Theory Take Over the World? | Ulrik Buchholtz

58 min

Why Didn't Homotopy Type Theory Take Over the World? | aboutlogic #25 From ordinal analysis to homotopy type theory: Ulrik Buchholtz (University of Nottingham) talks with Deniz and Thorsten about his journey from algebraic topology to Sol Feferman's unfolding program and from there into univalent foundations. Why do ordinals measure the strength of mathematical theories? What makes a definition predicative? And what is the one open problem that keeps homotopy type theory from taking over mathematics?

aboutlogic premises #10 | Is Unique Choice Really a Choice? (Follow-up to Giovanni Sambin)

32 min

Is Unique Choice Really a Choice? (Follow-up to Giovanni Sambin) | aboutlogic premises #10 If there is only one possible choice, are you making a choice at all? In this Premises, Thorsten and Deniz pick up the debate from our conversation with Giovanni Sambin: why does his minimalist foundation reject the Axiom of Unique Choice, while homotopy type theory proves it, and why does Lean make it so hard to use constructively? Join the Discussion: Have questions or thoughts to share? Drop a comment below and engage in a discussion with fellow viewers and experts.

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All episodes

aboutlogic: premises #11 | Category Theory: Algebra on Steroids?

29 min

Category Theory: Algebra on Steroids? | aboutlogic: premises #11 Is category theory just algebra on steroids? In this premises, Thorsten and Deniz give a pedestrian-speed introduction to category theory: structural mathematics, universal properties, duality and why products always come with coproducts, co-natural numbers, diagram chasing, and why homotopy type theory leads straight to higher categories. They also ask how category theory and type theory fit together and why Thorsten sees category theory as a way to structure ideas rather than the source of them.

aboutlogic #24 | Why Didn't Homotopy Type Theory Take Over the World? | Ulrik Buchholtz

58 min

Why Didn't Homotopy Type Theory Take Over the World? | aboutlogic #25 From ordinal analysis to homotopy type theory: Ulrik Buchholtz (University of Nottingham) talks with Deniz and Thorsten about his journey from algebraic topology to Sol Feferman's unfolding program and from there into univalent foundations. Why do ordinals measure the strength of mathematical theories? What makes a definition predicative? And what is the one open problem that keeps homotopy type theory from taking over mathematics?

aboutlogic premises #10 | Is Unique Choice Really a Choice? (Follow-up to Giovanni Sambin)

32 min

Is Unique Choice Really a Choice? (Follow-up to Giovanni Sambin) | aboutlogic premises #10 If there is only one possible choice, are you making a choice at all? In this Premises, Thorsten and Deniz pick up the debate from our conversation with Giovanni Sambin: why does his minimalist foundation reject the Axiom of Unique Choice, while homotopy type theory proves it, and why does Lean make it so hard to use constructively? Join the Discussion: Have questions or thoughts to share? Drop a comment below and engage in a discussion with fellow viewers and experts.

aboutlogic #23 | Rebuilding Mathematics from the Ground Up | Giovanni Sambin

57 min

What does set theory have to do with reality? Giovanni Sambin, Professor at the University of Padua and a leading figure in constructive mathematics, couldn't accept the standard axiomatic foundations of mathematics. So he spent nearly 50 years building an alternative from the ground up. He joins Deniz and Thorsten to discuss his new book Positive Topology, the culmination of decades of work connecting Per Martin-Löf's type theory, point-free topology, and his own "minimalist foundation" for mathematics.

Season 2 Recap: From Gödel to AI-Proved Math | aboutlogic #22

27 min

Season 2 Recap: From Gödel to AI-Proved Math | aboutlogic #22 Nine guests, four emerging themes, and one big question running through all of it: what happens to mathematics when symbolic reasoning and statistical AI finally meet? In this Season 2 recap, Thorsten Altenkirch and Deniz Sarikaya look back at conversations with Urs Schreiber, Joel David Hamkins, Dana Scott, Emily Riehl, Bernhard Fisseni, Bernhard Schröder, José Pérez Escobar, Jan von Plato, Mike Shulman, Tudor Achim, and Neil Ghani — and preview where Season 3 is headed.

aboutlogic: premises #09 | Why Symbolic AI Failed — and Then Won

31 min

Why Symbolic AI Failed — and Then Won | aboutlogic Premises #09 Symbolic AI — "GOFAI" — was meant to be the foundation of machine intelligence, and it failed spectacularly in the 1980s. In this premises episode, Thorsten and Deniz explore why, and how statistical AI, the technology that replaced it, may now be quietly bringing symbolic reasoning back — including a Platonic twist: if Plato thought the world of ideas came first, modern AI suggests structure and reasoning actually emerge only after fuzzy, statistical pattern recognition. They land on what Thorsten calls a "paradoxical synthesis": statistical AI winning the race is exactly what now makes rigorous, formally verified symbolic AI possible.

aboutlogic #21 | Category Theory Meets Agentic AI | Neil Ghani (Kodamai)

54 min

Category Theory Meets Agentic AI | Neil Ghani (Kodamai) Why does almost all agentic AI today run completely untyped — even though 40 years of type theory and category theory research says that's a mistake? Neil Ghani, Co-Founder of Kodamai, Professor of Computer Science at the University of Strathclyde and a world-leading authority in Applied Category Theory, joins Deniz and Thorsten to explain how the same mathematical structures used to reason about data types can bring trustworthiness, scalability, and adaptability to AI agents. The conversation ranges from the origins of container theory to why LLMs are fundamentally untyped, whether category theory is "abstract nonsense," the GOFAI failures of the 1980s, and how formal verification tools like Lean might be the unlikely savior of both mathematics and AI.

aboutlogic: premises #08 | Choice vs. Excluded Middle: A Constructive Paradox

33 min

Choice vs. Excluded Middle: A Constructive Paradox | aboutlogic: premises #08 Constructive mathematics is all about building things explicitly — so why does it reject the Axiom of Choice, which sounds trivial in a constructive context. In this Premises episode, Thorsten walks Deniz through Diaconescu's theorem: the surprising proof that the Axiom of Choice implies the Law of Excluded Middle, turning a seemingly innocent principle into full-blown classical logic. Using an intuitive type-theoretic explanation (starting with a very relatable glove-matching example), Thorsten builds up to Diaconescu's classic argument, touching on propositional extensionality, the difference between intensional and extensional predicates, and why the Axiom of Choice turns out to be a stronger form of "magic" than Excluded Middle itself.

aboutlogic #20 | Can AI Prove the Riemann Hypothesis? | Tudor Achim (Harmonic)

40 min

Can AI prove the Riemann Hypothesis? Tudor Achim, CEO of Harmonic and creator of Aristotle — the first AI to win IMO gold and solve Erdős problems using the Lean theorem prover — joins Deniz and Thorsten to discuss how mathematical superintelligence is transforming research, education, and the very nature of proof.

aboutlogic: premises #07 | Fixing Russell’s Paradox: The Birth of ZFC & Constructive Set Theory

30 min

Fixing Russell’s Paradox: The Birth of ZFC & Constructive Set Theory How did mathematicians fix Russell’s paradox and save set theory? In this aboutlogic: premises episode, Deniz and Thorsten explore the solutions that reshaped the foundations of mathematics. From Zermelo-Fraenkel (ZFC) axioms to constructive set theories (IZF, CZF). Discover how large cardinals, the continuum hypothesis, and the iterative conception of sets became central to modern set theory and why some mathematicians still prefer type theory for its structural and computational advantages. Your support helps us keep these conversations going! If you’d like to contribute, you can buy us a coffee here: https://buymeacoffee.com/aboutlogic Or become a channel member here on Youtube. We’d love to have your support! https://www.youtube.com/@aboutlogic Join the Discussion: Have questions or thoughts to share? Drop a comment below and engage in a discussion with fellow viewers and experts.

aboutlogic #19 | Homotopy Type Theory, Narya & the Future of Proof Assistants with Mike Shulman

1 hr 0 min

Homotopy Type Theory, Narya & the Future of Proof Assistants with Michael Shulman. How does homotopy type theory bridge the gap between abstract mathematics and computational proof systems? Mike Shulman (University of San Diego) joins Deniz and Thorsten to discuss his journey from topology to higher observational type theory, the development of the Narya proof assistant, and how these tools are reshaping the way we think about equality, equivalence, and computation in mathematics.

aboutlogic:premises #06 | What Is a Set? A Beginner’s Guide to Set Theory

27 min

What Is a Set? A Beginner’s Guide to Set Theory | aboutlogic: premises #06 In this aboutlogic: premises episode, Deniz and Thorsten explore the foundations of set theory. From Cantor’s groundbreaking ideas to Frege’s logical foundations and Russell’s paradox. Discover how sets evolved from simple collections to a rigorous mathematical framework, and why the power set, well-ordering, and the continuum hypothesis remain some of the most fascinating (and controversial) ideas in math.

aboutlogic #18 | The Hidden History of Logic: Jan von Plato on Gödel, Gentzen & Bernays

1 hr 2 min

aboutlogic #18 | What really happened in the 1930s logic revolution? Jan von Plato (University of Helsinki, ERC Grantee) joins Deniz and Thorsten to uncover the hidden collaborations, misunderstandings, and lost manuscripts that shaped modern logic. From Gödel’s unpublished notes to Gentzen’s lost normalization proof and Bernays’ pivotal role in Hilbert’s school, this episode reveals how the history of logic is far richer—and more interconnected—than we often assume.

aboutlogic: premises #05 | Dependent Type Theory: A Revolution in Math & Computer Science

27 min

Dependent Type Theory: A Revolution in Math & Computer Science | aboutlogic: premises #05 What makes dependent type theory so powerful? In this aboutlogic: premises episode, Deniz and Thorsten explore the evolution of type theory. From simple types to Pierre Martin-Löf’s groundbreaking dependent types. Discover how this innovation transformed mathematics and computer science by allowing types to depend on values, enabling more expressive and precise reasoning.

aboutlogic #17 | José Pérez Escobar – Wittgenstein, Turing & the Philosophy of Applied Mathematics

1 hr 15 min

aboutlogic #17 | Why is mathematics so effective in science? José Pérez Escobar (UNED, Madrid) joins Deniz and Thorsten to explore Wittgenstein’s philosophy of applied mathematics, the role of rules vs. structures in math, and how models shape our understanding of reality. From neuroscience to physics, José explains why mathematical models often act as rules of description rather than mere representations of reality and how this perspective resolves Wittgenstein’s "rule-following paradox." The conversation also dives into Turing’s structural view of math, the Dirac delta function controversy, and whether contradictions in mathematics are truly problematic.

aboutlogic: premises #04 | The Harry Potter Approach to Proof Assistants – Lean, Agda & AI

28 min

Your support helps us keep these conversations going! If you’d like to contribute, you can buy us a coffee here: https://buymeacoffee.com/aboutlogic How do interactive theorem provers like Lean and Agda change the way we teach and do mathematics? In this aboutlogic: premises episode, Deniz and Thorsten discuss the role of proof assistants in education, the differences between Lean and Agda, and how AI is transforming formal verification.

aboutlogic: premises #03 | Synthetic vs. Analytic Math: Inspired by Emily Riehl

38 min

Inspired by our conversation with Emily Riehl on higher category theory, this aboutlogic: premises episode dives into the synthetic vs. analytic approach in mathematics. Deniz and Thorsten explore how Euclid’s geometry, category theory, and higher categories embody the synthetic approach. Focusing on abstract structures and relationships rather than concrete coordinates or definitions.

aboutlogic #15 | Emily Riehl – Higher Category Theory, Homotopy & AI in Math

58 min

aboutlogic #15 | Emily Riehl (Johns Hopkins University) joins us to explore higher category theory, homotopy, and the role of AI in modern mathematics. From the foundations of category theory to the challenges of formalizing math with proof assistants like Lean, Emily shares her insights on synthetic vs. analytic approaches, the beauty of abstraction, and how AI is changing mathematical research.

aboutlogic: premises #02 | Hilbert’s Hotel & Cantor’s Infinity: The Story of Set Theory

26 min

Your support helps us keep these conversations going! If you’d like to contribute, you can buy us a coffee here: https://buymeacoffee.com/aboutlogic What is set theory—a foundation of math or a science of infinity? In this aboutlogic: premises episode, Deniz and Thorsten explore the history, paradoxes, and philosophical debates behind set theory. From Cantor’s diagonal argument to Hilbert’s Hotel and the role of ZFC, they discuss why set theory became the language of mathematics—and where its limits lie. Join the Discussion: Have questions or thoughts to share? Drop a comment below and engage in a discussion with fellow viewers and experts.

#14 aboutlogic | Dana Scott – Lambda Calculus, Forcing & the Foundations of Math

33 min

aboutlogic #14 | Turing Award winner Dana Scott joins us to discuss his groundbreaking work on lambda calculus, forcing, and Boolean-valued models and how these ideas revolutionized set theory and computability. From his collaborations with Kleene and Solovay to his thoughts on constructive mathematics, Scott shares insights into the history and future of logical foundations. Hear anecdotes about Gödel’s unpublished ideas, Einstein’s influence, and the telephone conversations that shaped modern logic.

aboutlogic #13 | Joel David Hamkins – Set Theory, Pluralism & the Multiverse View

1 hr 24 min

aboutlogic #13 | In this episode of aboutlogic, we’re joined by Joel David Hamkins, professor at the University of Notre Dame and a leading figure in set theory, mathematical logic, and the philosophy of mathematics. Joel shares his insights into the multiverse view of set theory, a perspective that challenges the traditional "universe view" by embracing a pluralistic approach to mathematical truth. We explore how this view connects to constructivism, potentialism, and the foundations of mathematics, and discuss its implications for understanding concepts like the Continuum Hypothesis (CH) and the nature of mathematical reality. Joel also reflects on the historical contingency of mathematical axioms, the role of categoricity in mathematics, and how different philosophical perspectives, such as Platonism, formalism, and fictionalism, shape the way mathematicians approach their work. Whether you're a mathematician, philosopher, or simply curious about the foundations of logic, this conversation offers a deep dive into the diverse and evolving landscape of mathematical thought.

aboutlogic #12 | Urs Schreiber – Quantum (Physics, Computing), Topos & Homotopy Theory

59 min

aboutlogic #12 | In this episode of aboutlogic, we’re joined by UrsSchreiber, a senior scientist at New York University Abu Dhabi. Urs shares insights into his work at the intersection of quantum physics, topos theory, and homotopy type theory. We explore how these advanced mathematical frameworks help address fundamental questions in physics, from understanding gauge fields to the role of higher category theory in describing the universe. Urs also discusses the historical and philosophical connections between physics and logic, and how modern mathematics is shaping our understanding of reality.

aboutlogic #11 | Season 1 Recap: Feedback, Highlights & Season 2 Preview

1 hr 3 min

aboutlogic #11 | In this special Season 1 Recap of aboutlogic, Deniz and Thorsten reflect on your comments and feedback, revisit some of the most intriguing topics, and look back at all the incredible guests from the first season. What were the highlights? What did we learn? And what’s in store for Season 2? Join us for a wrap-up filled with insights, gratitude, and a sneak peek at what’s next.

aboutlogic #10 | Seunghyun Song & Jordi Fairhurst – ABC Conjecture, Epistemic & Linguistic Justice

52 min

aboutlogic #10 | In this episode, we talk with Seunghyun Song and Jordi Fairhurst about the ABC conjecture, the importance of epistemic justice, and the role of linguistic justice in non-Western mathematical traditions. How do diverse perspectives reshape our understanding of mathematics? Join the Discussion: Have questions or thoughts to share? Drop a comment below and engage in a discussion with fellow viewers and experts.

aboutlogic #07 | Alexander Steen – Interactive Theorem Provers, Legal Reasoning, Non-Standard Logics

49 min

aboutlogic #07 | We’re joined by Alexander Steen, who works on logics to be used in legal contexts. In this episode, we talk about the relationship between ethics and law, how good old-fashioned artificial intelligence can help legal practitioners, and how to use theorem proving practices for this. Join the Discussion: Have questions or thoughts to share? Drop a comment below and engage in a discussion with fellow viewers and experts.

aboutlogic #05 | Steve Awodey – Homotopy Type Theory, Logic & Philosophy

51 min

We’re joined by Steve Awodey, one of the founders of Homotopy Type Theory. In this episode, we talk about the relationship between philosophy and mathematics, the main ideas behind geometric thinking and logic, and how all of this connects to computer science. Join the Discussion: Have questions or thoughts to share? Drop a comment below and engage in a discussion with fellow viewers and experts.

aboutlogic #04 | Graham Priest – Working with Contradictions & Paraconsistent Logics

46 min

Today we’re joined by Graham Priest from New York, a philosopher who also studied mathematics and is well known for many things. In particular, we will talk about contradictory logics – logics where we can work with a contradiction without being able to prove everything. We’ll also discuss non-standard topics, including non-standard arithmetic and non-standard set theory, and how all of this is philosophically motivated. Join the Discussion: Have questions or thoughts to share? Drop a comment below and engage in a discussion with fellow viewers and experts.

aboutlogic Teaser | A Podcast on Logic, Mathematics & Philosophy

1 min

Welcome to aboutlogic, a dedicated space where the realms of logic, mathematics, philosophy, and computer science converge. Every two weeks, we feature in-depth conversations with some of the most brilliant minds in these fields, who were somehow stupid enough to speak with us.

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