Steve Awodey - Intentionality, Invariance and Univalence

19:59 "Q: What is an equivalence class under isomorphism? A: A set!" and the meaning of a proposition in intuitionstic logic is the set of its proofs. Now what a set is is a matter of taste, but Set Theory is the first-order theory of extensional equality and one binary operator. And a theory is a set of formulae closed under deduction. A theory is characterised by a signature. The language of a signature is the set of all well formed sentences built from the symbols in that signature together with the symbols in the logical system. See Standard ML For The Lady Programmer. 

For more on infinity-goupoids and homotopy see Wikipedia's page Homotopy hypothesis, and John Baez's slides: The Homotopy Hypothesis.

See also Daniel Tubbenhauer on Diagrammatic Algebra and Quantum Topology.

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I talked a bit about this idea last night:


And I just noticed that YouTube has deleted all of Norman Wildberger's videos, or he deleted them, which seems unlikely:

No, it was vandalism. See his message on Pateron:

I have been hacked!! (2 days ago)

Dear Patrons, It appears I have been hacked in a major way. Please be patient as I try to unravel this nightmare. And disregard and crazy messages etc . I have been busy getting together interesting new videos on rational fourier series and other things, but that will have to wait.

It looks like my entires YouTube channel(s) are gone..

Sorry about that, will of course try to remedy.

All the best.

Norman

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