Cathal Woods Introduction to Reasoning. A critical thinking textbook, covers propositional and categorical logic, real world reasoning, and inductive logic. I use this in my critical thinking class. Between this and For All X you can cover all the traditional topics in logic and critical thinking courses.
Other Online Logic Textbooks
Paul Teller A Modern Formal Logic Primer Originally published in 1989 by Prentice Hall, this book fell out of print and the copyright was returned to the author. Teller then generously put the whole thing on line for free. There is some old free software associated with this text, which I could not get to work on my windows 64-bit machine, despite the inclusion of material that is supposed to help me do just that.
Tony Roy Symbolic Logic: An Accessible Introduction to Serious Mathematical Logic Roy has put the .pdf files for this text online for free with a note saying to give him feedback if you use the material. There are no source files or creative commons license.
This book was written as an introductory text for student who are going on to more advanced courses. The original version introduced sentential and predicate logic together, but now you can download a version of the early chapters that just covers sentential logic. The second half of the book is all about metalogic, including soundness and completeness results for various systems.
Paul Herrick Introduction to Logic Although this was designed in conjunction with an open access course, the text is not completely free. The electronic version is $30 from CourseSmart, because the author waived his royalties. The paper version is $60 from Oxford University Press. The whole thing is wrapped in DRM, so you can’t just pass around a .pdf file or edit the original source files to your liking.
The chief advantage of this book is the wealth of free online materials. The open courseware for the book lets you download an angel package containing a couple dozen quizzes and exams, PowerPoints, online lectures and links to the videos Herrick made on Youtube, like this one. The videos are well produced and shot in pretty outdoor locations. There doesn’t seem to be a Youtube channel or other portal that gathers them together, though. Additional resources are available at the webpage for Herrick’s previous logic textbook, The many worlds of logic
Ian Barland, et al. Intro to Logic Written for a logic course in the computer science department at Rice University. It begins by trying to motivate the study of logic using a deceptive proof that 90 = 100. Students are meant to see the need for logic to understand what is wrong with the proof.
Wikibooks Formal Logic For math-oriented students. Begins with a discussion of set theory.
Institutions with open logic courses
MIT: Logic 1: 24.241 Not much here. Class based on Bergmann, Merrie, James Moor, and Jack Nelson. The Logic Book. Contains homework exercises with answers, tests without answers, and outlines of lectures. Homework exercises often just ask you to work certain problems in the book.
Logic Software and Teaching Websites
Christian Gottschall’s Gateway to Logic has a truth table builder, proof checker, several proof builders, including one that works with the axioms from Principia Mathematica. The Fitch-style proof builder is compatible with For All X, the Lorain County Remix
Wandering Mango Deductions says it is compatible with many textbooks. Website does not seem to be working properly.
General Logic and Critical Thinking Resources
Introduction to Reasoning by Cathal Woods. See my note under the heading “Highly Recommended” above.
General Opencourseware Pages
Open Culture’s list of 500 free online courses
Open Culture’s list of 150 free textbooks.
Yale Open Courseware. I strongly recommend the Greek history course taught by Donald Kagan. I listened to his lectures during my commute one semester and it filled in a lot of my knowledge of the historical background for ancient philosophy. Death taught by Shelly Kagan and Tamar Gendler’s course on the science of human nature have video and audio. No logic classes yet.
Peter Adamson’s History of Philosophy Without Any Gaps This is my favoritest philosophy resource online. I generally listen to new episodes as soon as they are available. Adamson gives you lively and funny tour that lets you know about all those parts of the history of philosophy that got skipped in school.
MIT Open Courseware They have some content for almost all their linguistics and philosophy courses, but sometimes it is just lecture notes. About a dozen courses have multimedia content. The logic class doesn’t have much content.
Webcast.Berkeley Courses by Searle and the philosophy of language and society, and by John Campbell on the philosophy of mind. No logic courses.