Skip to main content
note
This page was translated from the German original, partly by machine. Some passages may read awkwardly or contain inaccuracies. When in doubt, please read the original.

1. Introduction to Critical Thinking

 

Wireless Philosophy, Fundamentals, 9:50. Original title: CRITICAL THINKING - Fundamentals: Introduction to Critical Thinking [HD]

Summary​

Geoff Pynn (Northern Illinois University) opens the series with three questions: what is critical thinking, what is an argument, and what is the difference between deductive and ampliative arguments?

What is critical thinking?​

Fundamentally, critical thinking is about making sure that we have good reasons for our beliefs.

The whole lesson is built around one small scene. You and a friend are talking about who will be at tonight's party, and she says confidently: "Monty won't be at the party." Not sure whether to believe her, you ask the natural follow-up question, "Why do you think so?" She could answer in three ways:

  • "I can't stand him, and I want to have a good time."
  • "He's really shy, and he rarely goes to parties."
  • "He's in Beijing, and it's impossible to get here from Beijing in an afternoon."

The first answer gives no good reason to believe that Monty will stay away. The second does: if he is shy and rarely goes to parties, it is probable that he will not be there. The third does too, and more strongly: if he is in Beijing and cannot get back in an afternoon, his absence is guaranteed. Noticing differences of exactly this kind, telling good reasons from bad ones, is what exercising critical thinking consists in.

What "good" means here​

The word "good" carries no moral weight in this context. Believing something on the basis of a bad reason is not wicked or evil. "Good" is tied to truth: a good reason is one that makes the belief probable, that is, likely to be true, and the very best reasons make it certain.

That is also why critical thinking matters. Rational people want to have true beliefs and want not to have false ones, and the best way to manage that is to form beliefs only when we find good reasons for them.

What is an argument?​

An argument is a set of statements that together comprise a reason for a further statement. The statements that provide the reason are the premises, and the statement they support is the conclusion:

Premise 1: Monty is really shy.
Premise 2: Monty rarely goes to parties.
Conclusion: Monty won't be at the party.

A good argument is one whose premises give a good reason for the conclusion, that is, they make it likely to be true. In that case we say the premises support the conclusion. Bad arguments fail to do so.

The first answer, taken as an argument, is bad: that your friend can't stand Monty and wants a good time is simply unrelated to whether he shows up; it does nothing to make the conclusion more likely. Pynn adds an instructive twist, though. Add a background premise and the same statements become a good argument: if your friend is the person deciding who gets invited, then her dislike of Monty does give you reason to think he won't be there, because it gives you reason to think she never invited him.

Deductive and ampliative arguments​

Both good answers support the conclusion, but not in the same way:

  • The Beijing argument is deductive. If its premises are true, the conclusion must be true; thinking through the information in the premises is all it takes to deduce it.
  • The shyness argument is ampliative. Even with true premises the conclusion might still be false: Monty could get over his shyness, suspend his usual policy, and turn up unexpectedly. Unlikely, but possible. The premises make the conclusion probable without guaranteeing it.

Ampliative arguments can be very good arguments; they are simply not deductive. This is why it matters to know which kind of argument we are dealing with before evaluating it. If an argument is meant to be deductive and the premises turn out not to guarantee the conclusion, that is usually a good reason to reject it. Raising the same objection against an ampliative argument misses the point entirely: that the premises do not guarantee the conclusion is taken for granted there, since what the argument offers is grounds for thinking the conclusion probable.

Key takeaway​

Critical thinking is making sure we have good reasons for our beliefs, where a good reason is one that makes a belief probable or even certain. Arguments are how reasons get laid out, and knowing what type of argument we face is essential to knowing which tools to use in evaluating it.