4. Critical Thinking's Dirty Secret: The Importance of Background Knowledge


In this lecture I want to talk about the fourth item on our list of the five essential components of critical thinking, five areas of study or personal development that you need to pay attention to if you really want to develop as an independent critical thinker.

Just to review, our list includes logic, argumentation, rhetoric, background knowledge, and finally a certain set of attitudes and values. Here we’re going to talk about the importance of background knowledge to critical thinking.

I titled this episode “Critical Thinking’s Dirty Secret”, but what I really mean is Critical Thinking instruction’s dirty secret. For anyone who teaches critical thinking, or for the industries devoted to cranking out textbooks on critical thinking, a guiding premise of the whole enterprise is that critical thinking skills can actually be taught, and the crude version of this view is that if students can master some formal and informal logic and some fallacies, they’ll be better critical thinkers.

The dirty secret of critical thinking instruction, which everyone knows if they’ve done it for a while, is that while logic and argument analysis are necessary components of effective critical thinking, they aren’t sufficient, not by a long shot.

What’s missing is the importance of background knowledge. Background knowledge informs critical thinking at multiple levels, and in my view it’s among the most important components of critical thinking. But you can’t teach background knowledge in a one-semester critical thinking course. Or at least, you’re very limited in what you can teach.

That’s the dirty secret that most textbooks avoid talking about. The most important component of critical thinking can’t be taught, at least not in the way you can teach, say, formal logic and fallacies. Background knowledge comes from learning and living in the world and paying attention to what’s going on. Mastering this component of critical thinking requires a dedication to life-long learning, a genuine openness to different points of view, and a certain humility in the face of all that you don’t know. This isn’t a set of skills you can master with worksheets and worked examples. This is a philosophy, this is a lifestyle choice. Textbooks don’t talk about this. Or at least not as much as they should.

There are at least two importantly different types of background knowledge that are relevant to critical thinking, and they each deserve attention. In this lecture I want to focus on background knowledge involved in evaluating arguments on a specific subject matter. Next lecture I’m going to talk about the kind of attitude you need to have if you want to really understand the background on all sides of an issue.

i. Background Knowledge of Subject Matter

Okay, let’s remind ourselves of the basic elements of argument analysis. You’re given an argument ― it’s a set of premises from which a conclusion is supposed to follow.

i. Argument Analysis: Does the Conclusion Follow?

Argument analysis involves two distinct steps. The first is evaluating the logic of the argument. When you’re evaluating logic you’re asking yourself, does the conclusion follow from these premises? The key thing to remember about this step is that it’s an exercise in hypothetical reasoning. You assume, for the sake of argument, that the premises are all true, and you ask yourself, if the premises are true, how likely is it that the conclusion is also true? This is a question that you can answer using basic logical techniques ― you can teach this. Students can learn to distinguish good logic from bad logic with textbook exercises, and they can learn to extract the logical structure of real-world arguments and evaluate the logic. If the logic is bad then the argument is bad. But if the logic is good, then we move to the second step in argument analysis.

ii. Argument Analysis: Do We Have Good Reason to Accept the Premises?

The second step is where you ask the question, but are the premises in fact true? Do I actually have good reasons to accept them? If we, or the intended audience of the argument, doesn’t have good reasons to accept them, then we have reason to reject the argument, even if the logic is good, because we’ll judge that it rests on faulty or contentious or implausible premises.

Now here’s the point I want to emphasize: This step, where you assess the truth or falsity of the premises, is not something you can teach in a logic or critical thinking class. And the reason why is obvious. This is a question of background knowledge. Premises are judged plausible or implausible relative to your background knowledge, what you bring to the table in terms of your knowledge of the subject matter. If you’re ignorant about the subject matter then you’ll make lousy judgments, it’s that simple.

iii. An Example: The Mars Hoax

Let me give you an example. We had a friend over to our house and she mentioned that she’d received an email about a spectacular appearance of Mars in the night sky that we should be on the lookout for some time in August. The claim was that Mars was going to be so unusually close to the earth at that time and that it would appear as large as the Moon to the naked eye. It’ll look like the earth has two moons.

Now, my “bs” detector went off right away. I just knew this was false, there’s no way that Mars is ever going to look as big as the Moon. Unless it’s knocked out of its orbit, it’s astronomically impossible. But our friend wasn’t an amateur astronomer, it didn’t raise any red flags for her, she didn’t have any reason to doubt it. In this case, her lack of background knowledge made her susceptible to a hoax, and no amount of training in formal logic would have made her less susceptible to this hoax.

By the way, if you’re interested (and I hadn’t heard of this before this incident) if you google “mars hoax” you’ll see that this has been circulating for quite a while.

iv. The Moral: All the Logic in the World Won’t Make Up for Ignorance

The moral of this story is simple. If you want to become an independent critical thinker about a particular subject matter, you need to learn something about that subject matter. If you want to argue about Obama’s health care plan you need to learn something about the plan and the economics and politics and ethics of health care. If you want to argue about how to address global climate change you need to learn something about the scientific and economic and political and ethical issues that bear on this question. And similarly for issues in history, religion, culture, media, science, philosophy ― you’ve got to learn something about the subject matter. All the logic in the world won’t make up for ignorance.

Now, I know this is easier said than done, but there’s no avoiding it, no escaping it. Critical thinking demands a commitment to life-long learning. This is part of what it means to take responsibility for your own beliefs.