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What is Logic?

What is Logic?

This is the homepage of my draft textbook, What is Logic?. The DRAFT status of this book is very important: Portions of it are substantially incomplete. If, however, you find any errors, please let me know.

There is a supplementary series of youtube videos covering content in this book.

Recent updates:

  • 2026-02-12: Uploaded draft 2026-02-12, which distinguishes classical from non-classical valuations at the start of Section 7.4, corrects the annotations for example 7.5.15, and added some info to Chapter 21.
  • 2026-02-02: Uploaded draft 2026-02-02, which adds the caveat that i,i+1<n to the rules for applying syllogistic axioms and fixes some typos in Chapter 11.
  • 2026-01-23: Uploaded draft 2026-01-23, which removes section 6.4 (so previous section 6.5 is now 6.4, and previous section 6.6 is now 6.5.)