Critical Thinking: Arguments and Reasoning

What is Critical Thinking?

• Fundamentally, critical thinking is about ensuring you have good reasons for your beliefs.

• It involves distinguishing between good and bad reasons for believing something.

• A good reason is one that makes a belief probable or likely to be true; the best reasons guarantee the belief.

• The term "good" here relates to truth, not morality.

• Critical thinking is important because rational people want their beliefs to be true and avoid false beliefs.

What is an Argument?

• An argument is a set of statements (premises) that together provide a reason for a further statement (conclusion).

• Premises: The statements that offer the reason.

• Conclusion: The statement that the premises support.

• A good argument has premises that make the conclusion likely to be true; i.e., the premises support the conclusion.

• Critical thinking involves evaluating arguments to determine if their premises support their conclusions.

• Example 1:

  • Premise 1: "I can't stand Monty."

  • Premise 2: "I want to have a good time."

  • Conclusion: "Monty won't be at the party."

  • Evaluation: Bad argument because the premises don’t make the conclusion more likely.

• Example 2:

  • Premise 1: "Monty's in Beijing."

  • Premise 2: "He can't get from Beijing to the party in time."

  • Conclusion: "Monty won't be at the party."

  • Evaluation: Good argument because the premises guarantee the conclusion if they are true.

• Bad arguments can sometimes be improved with additional background premises.

Deductive vs. Ampliative Arguments

• Deductive Argument: An argument where the premises guarantee the truth of the conclusion.

  • If the premises are true, the conclusion must be true.

  • Example:

    • Premise 1: "Monty's in Beijing."

    • Premise 2: "He can't get from Beijing to the party in time."

    • Conclusion: "Monty won't be at the party."

• Ampliative Argument: An argument where the premises make the conclusion probable but do not guarantee it.

  • The conclusion could be false even if the premises are true.

  • Example:

    • Premise 1: "Monty's really shy."

    • Premise 2: "He rarely goes to parties."

    • Conclusion: "Monty won't be at the party."

• Evaluating Arguments:

  • It is important to know whether an argument is deductive or ampliative when evaluating it.

  • If a deductive argument fails to guarantee the conclusion, it can be rejected.

  • For ampliative arguments, the premises do not need to guarantee the conclusion; they only need to make it probable.

Summary

• Critical thinking is about having good reasons for our beliefs, where a good reason makes the belief probable.

• An argument consists of premises that provide a reason for a conclusion.

• In a good argument, the premises support the conclusion.

• A deductive argument guarantees the conclusion if the premises are true, while an ampliative argument makes the conclusion probable but does not guarantee it.