The red argument is the first response that she gave, two premises, "I can't stand Monty" and "I[br]want to have a good time." And the conclusion is "Monty[br]won't be at the party." And the third argument,[br]which we'll put in purple, consisted also of two premises, "Monty's in Beijing" and[br]"He can't get from Beijing to the party in time, so[br]he won't be at the party." Now, as I indicated[br]before, the first argument is not good, while the[br]purple argument is good.
And here I can explain a[br]little bit more about why.
The fact that your[br]friend can't stand Monty and wants to have a good[br]time doesn't do anything to make it more likely[br]that Monty won't be there. In the purple argument,[br]though, the premises, if they're true, they guarantee[br]the conclusion is true. The truth of the premises[br]guarantees the truth of the conclusion, and so[br]in the purple argument, the premises do support the conclusion.Good arguments support their conclusions, and bad arguments don't[br]support their conclusions.So a key part of critical[br]thinking is learning to evaluate arguments to determine whether or not they're good or bad, that is, whether or not their premises support their conclusions.So critical thinking is making sure we have good reasons for our beliefs, and so one of the essential[br]skills that you learn when you're studying[br]critical thinking is how to distinguish good reasons[br]for believing something from bad reasons for believing something.Now, it's worth saying something about how I'm using the term "good" here.Similarly, it's not morally[br]wrong, or evil, or wicked to believe something on[br]the basis of a bad reason.Rather, here, what it is to[br]say that a reason is good is closely tied to the notion of truth.First, she might say, "I can't stand him, and I want to have a good time." Second, she might say,[br]"Well, he's really shy, and he rarely goes to parties." And third, she might say, "He's in Beijing, and it's impossible to get here from[br]Beijing in an afternoon." The first response that she gives you does not give you a good reason to believe that Monty won't be at the party.The second reason,[br]though, is a good reason to believe that Monty[br]won't be at the party. I teach at Northern Illinois University, and this is an introduction[br]to critical thinking. And third, what's the difference between deductive and ampliative arguments? Well, fundamentally, critical thinking is about making sure that you have good reasons for your beliefs. So suppose that you and your friend are talking about who's[br]gonna be at tonight's party.In this lesson, we're gonna[br]talk about three things. And she says to you, quite confidently, "Monty won't be at the party." You're not sure whether[br]or not to believe her, so it would be natural[br]for you to follow up by asking, "Why do you think so?