I begin my Logic course with a selection from Descartes’s Discourse on Method (parts of §§1 and 2), because for me that book lays out the most important stakes of the course. Descartes suggests that we all have equal capacity to judge, and that therefore we should be able to compare reasons and methods rather than just fighting about differing conclusions. When I teach logic, my course is intended to help my students make more rigorous and intellectually honest arguments and to do a better job engaging with the opposing views of others.

I have split my course between formal and informal logic. This in itself is not an unusual approach, but one unusual feature of my syllabus is that I begin with the formal logic. When I have tried starting with informal logic, I have found that I get students who have a hard time distinguishing premises from a conclusion, tracking logical inferences, and separating the question of an argument’s strength from the question of whether or not they agree with the conclusion. An eight-week “conditioning” sequence in formal logic seems to really help here, and I have found that the shift to argument diagramming in the second half of the semester now feels like a natural progression into content rather than the arbitrary imposition of form onto recalcitrant matter.

I teach my students a very “stripped-down” version of SD:

• We use negation, conjunction, disjunction, and conditionals; I don’t use biconditionals in the course.
• I use the derivation rules for SD presented by Bergman, Moore, and Nelson in their The Logic Book; with the absence of biconditionals, this means that we use only nine rules for derivations.

The reason for this pared-down version of SD, rather than the more popular and expansive SD+, is that SD+ is intended to reflect common sense and natural reasoning. I know that this sounds weird—but the arbitrarily-limiting formality of basic SD is actually why I chose it! Derivation is presented to the students as a kind of a game or a logic puzzle: Get from the starting axioms to the goal inference using only these nine rules. Most students—especially the quick thinkers—will intuitively see something like a disjunctive syllogism: If A v B is true, and A is false, then B must be true. The frustrating thing about Bergman, Moore, and Nelson’s SD rules is that it forces you to slowly unpack this inference using the “disjunction elimination” process. Students can’t just say, “But I know it works!” Instead, they have to be able to show, step by step, how to make the rules say it. In addition to being good practice in formal reasoning, I also like to show my students that this is the same skill at work in law, in computer programming, and even in formatting academic articles according to a stylesheet!

When we turn to informal logic, my approach is a bit more traditional: Argument diagramming has a proven track record for improving critical thinking skills, and of course no critical thinking course would be complete without a unit on informal fallacies. But the defining feature of the informal half of my logic course is the three-essay sequence:

• Coming back from the midterm, I have my students write a short, argumentative essay: It can be on any topic of their choosing, as long as it is something they have a strong stance on—I regularly have students choose topics ranging from abortion, religion, and capital punishment, to which video game or pizza topping is best—and as long as it’s something they’ll want to spend the next eight weeks on.
• For Essay #2, I assign each student a new thesis: the opposite of whatever they argued in Essay #1. If a student has argued that Breath of the Wild is the greatest video game of all time, I assign them the thesis that Breath of the Wild is wildly overrated. If a student has argued that abortion ought to be illegal, I assign them the thesis that abortion ought to be widely available and legally protected. Furthermore, Essay #2 comes with a very strict constraint: No fallacies, no rhetorical appeals to the already-convinced, and no appeals to emotion. I ask the students for a rigorous, compelling argument, and I suggest that they do some research to try to understand where “the other side” is coming from. Many students find that they really enjoy this challenge, and of course some come to me quite frustrated, convinced that there’s no way to make a logical argument for the other side. (In some rare cases they are right, and it turns out that they have chosen to argue about something trivial—but of course in most cases they just need some assistance tracking down better opponents and reading a bit more charitably.)
• Essay #3 allows students to again take up any side of the argument that they wish, and every semester I have at least one student who has changed their mind over the course of writing Essay #2. With Essays 1 and 2 in hand, the students can now argue for their thesis by engaging with strong counterarguments and objections.

By the end, my students are making stronger arguments that try to engage with and convince the opposing side of a debate. Most students report getting a lot out of the experience, and they come away with tools and skills that they can directly apply in their other courses and beyond.

Finally, many students choose to take a logic course because they’ve been told that it will help them do well on the LSAT, and you’ll notice that I have a “bonus” unit on graduate school exams at the end of my course. However, since the LSAT has now dropped the logic games section (and replaced it with a second Logical Reasoning section), that bonus unit mostly just shows my students how useful the argument diagramming and fallacy units were!

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