Desirable features in an introductory logic textbook?

Question

I have been very unsatisfied with the quality of the free, open-source textbooks in logic I have found so far. Some, like P. D. Magnus's forall x and the wikibooks Formal Logic text seem overly mathematical and too fast paced. Others, like Velleman's blogic, don't seem to be available in book form. There are plenty of nice introductory books in logic, like Barwise & Etchemendy, Hurley, Copi & Cohen, etc. But those are all prohibitively expensive. What I am proposing to do is to write a such a textbook and release it for free in pdf and latex source code with a creative commons license (CC-BY-NC-SA probably). I want to cover basically the same information as Barwise & Etchemendy, and at about the same pace. The class I am envisioning is a standard 1 semester class in first order logic through identity.

What I want to know is which features the community here think make for an excellent introductory textbook? Here are some specific things I'd like feedback on:

• What kind of problem sets do you find most helpful? Do you like having a complete answer key, or are selected solutions in the back of the book sufficient?
• Do you think it is useful to include informal topics, i.e. fallacies?
• What about a short unit or two on inductive logic?
• Is it worth even talking about Venn Diagrams, or should we just jump right into the mechanics of contemporary quantification theory?
• Do you ever use the index or glossary of a textbook?
• How about short little bios of famous logicians like Ruth Barcan Marcus in a sidebar?

My ultimate goal here would be to create the text and then start a kickstarter to crowd-fund the development of a set of software packages for the student and instructor. If there were enough funding, I might even consider doing the Khan Academy thing and creating a series of videos teaching through the book. What do people think about that? What kind of software would be useful to you, as a student or instructor? Are there any logic teachers here interested in the "flipped classroom" approach that think these tools would be helpful to them?

Answer 1

There's quite a few questions in there, but I'm interested in the topic as well. I share your general frustration. I will be teaching a "critical thinking" course this upcoming semester, and the number of qualifying textbooks is limited. They tend either to bore me to tears or rapidly jump to complexity.

First, I think at least in the initial units, it would be helpful to provide a full answer key. For later units, it may be acceptable to leave at least some questions as "exercises for the readers."

Second, the inclusion of fallacies seems to be wholly or at least generally absent from texts that consider formal logic. I think for students that take it seriously, they will recognize things as fallacious on their own. At the same time, I do cover some fallacies myself. The problem is that fallacies tend to involve judgments calls -- is something a slippery slope or a legitimate consequence of a chain rule? Is it an equivocation or are the two really the same? Was that a biconditional and valid or a conditional and thus affirming the consequent? Moreover, I've always run into taxonomy problems regaring some fallacies (genetic or ad hominem?)

Third, inductive logic also tends to turn out to be a question of individual method. There's Mill's methods and a crap ton of other ways to do it.

Fourth, I think Venn diagrams work for some but not all students. I don't mind teaching them, but I do question their value -- at least the AEIO subset that's normally taught. But I think they do help for students overall.

Fifth, I don't use the index.

Sixth, I think the biographies would be only minimally important. I would be more interested in them if they brought up thinkers who faced and solved problems -- e.g. Austin and Searle and the limits of logical positivism, the barber problem, Wittgenstein's disappointment with logic, Lewis's bullet-biting williningness to accept an infinite number of worlds as all real.

I' m interested in flipped classroom as well. My one worry is that students will be rocking their cell phone while the computer goes through the lecture... and then not sufficiently prepared for class.

Answer 2

Fallacies are a good idea, but they should be also be subject to critical inquiry otherwise they may become sacred cows in the minds of the student.

Exercises with full solutions are great for motivated students. Even better if there are hints.

Venn diagrams are good because they are visual. You don't want your textbook to be a wall of text, or do you?

Bios are nice to give some backfrop to the discussion. But I think it might be even nicer to have a discussion of the tradition of logic and its many modalities to give a greater depth and coherence to the subject.