Textbook for Calgary's Logic II course based on the Open Logic Project. Covers naive set theory, first-order logic, sequent calculus and natural deduction, the completeness, compactness, and Löwenheim-Skolem theorems, Turing machines, and the undecidability of the halting problem and of first-order logic.

Thinking Well is a Creative Commons Logic and Critical Thinking Textbook. The emphasis is on clarity of step-by-step instructions and a dialogic format to make it as accessible to a wide variety of ages of skill-levels as possible.

Words of Wisdom can come from anyone. In this text we discuss topics ranging from "Are Humans good by nature?" to "Is there a God?" to "Do I have the right to my own opinion?" Philosophy is the study of wisdom, and can emerge in our conversations in places like social media, in school, around the family dinner table, and even in the car. The text uses materials that are 2,500 years old, and materials that were in the news this year. Wise people come in all shapes and types, and from every culture on earth. We have poetry and folktales, sacred writings and letters. Dialogues and interviews, news columns, podcasts, Ted Talks, You Tube recordings and even comedy are all a part of the content in this text.You will be most successful using this collection this on line.

forall x is a full-featured textbook on formal logic. It covers key notions of logic such as consequence and validity of arguments, the syntax of truth-functional propositional logic TFL and truth-table semantics, the syntax of first-order (predicate) logic FOL with identity (first-order interpretations), translating (formalizing) English in TFL and FOL, and Fitch-style natural deduction proof systems for both TFL and FOL. It also deals with some advanced topics such as truth-functional completeness. Exercises with solutions are available. It is provided in PDF (for screen reading, printing, and a special version for dyslexics) and in LaTeX source code. A proof editor/checker for the proof system used is available at http://proofs.openlogicproject.org/.