Analysing fallacies to improve our thinking has a long tradition.
In On Sophistical Refutations, Aristole outlines a number of sham arguments that have a certain likeness to genuine ones. These include the fallacies of composition and division, begging the question, and affirming the consequent.
Nearly 2000 years later, John Locke outlined many of the ad- fallacies - ad hominem, ad verecundiam, and ad ignorantiam - in An Essay Concerning Human Understanding.
And much more recently (in philosophical terms at least), Charles Hamblin (1970) renewed interest in fallacies as a way to teach critical thinking.
And it's easy to understand why.
Fallacies are concrete examples of poor reasoning. They provide students with exemplars to identify common patterns of bad arguments, as well as a common language to label and discuss them.
What's more, spotting fallacies in the media and political discourse is fun. Well ... for some of us anyway.
But simply teaching students about fallacies is far from a sure-fire way to improve their thinking skills. Fallacy-based approaches can also present a number of problems.
The problem with fallacies
Fallacies provide us with labels to name patterns of poor reasoning.
But this strength is also a weakness. That's because the long (nearly 2500 year) history of fallacy theory has resulted in a great deal of duplication and overlap.
For example, in 1724 Isaac Watts described argumentum ad populum as a public appeal to the passions.
Today, we might call it appeal to popular opinion or the bandwagon fallacy but Wikipedia shows that it has been variously labelled the common belief fallacy, appeal to the majority, appeal to the masses, appeal to popularity, the argument from consensus, the authority of the many, consensus gentium , the democratic fallacy, appeal to the mob, and even truth by association.
This excess-of-names is made worse by the fact that over time, these labels have also changed meaning.
When Locke wrote of argumentum ad hominem (playing the person rather than the argument), he described it as a way "to press a man with consequences drawn from his own principles or concessions" (Book 4 Chapter 17).
This conception of ad hominem is a far cry from what we typically associate with the term today - to attack the character or motive of a person, rather than the content of their argument.
But perhaps the biggest problem with fallacy-based approaches to critical thinking is that the various fallacies are neither mutually exclusive nor collectively exhaustive.
A single argument can contain multiple fallacies and it's quite common to see a classroom discussion getting bogged down on whether an argument commits the fallacy of x, y, or z (and made even worse when half the class is calling them p, q, and r).
What's more, there are far more possible patterns of poor reasoning than named fallacies. No single taxonomy of fallacies could ever hope to identify them all.
It turns out that focusing on which fallacy a particular poor argument commits, rather than why it is a poor argument, wont improve critical thinking any more that being able to correctly identify a bad serve will improve your tennis game.
Making fallacies work
Just because these problems can arise, doesn't mean the have to. To ensure a fallacy-based approach to critical thinking actual improves critical thinking, keep these points in mind:
Get clear about what we mean when we talk about critical thinking. There are lots (and I mean lots!) of different and often conflicting definitions of critical thinking.
We prefer an actionable definition that simplifies its pedagogy:
Critical thinking is thinking that is both metacognitive and evaluative according to norms of rationality (where what we are evaluating is the quality of our thinking).
Use activities like the identification of fallacies as an opportunity to have students reflect on and evaluate their thinking..
Since critical thinking means thinking about our thinking and evaluating it, we can improve our student's (and our own) critical thinking by getting them to do exactly that.
Fallacies provide an excellent opportunity to get students thinking about why arguments are good or bad, strong or weak, justified or unjustified.
They also provide us with concrete examples that can be contrasted with good reasoning. When is an appeal to authority justified and when is it not? What is it about someone or something that makes them an authority?
With these points in mind, you'll be able to avoid the problems and make a fallacy-based approach to critical thinking work.