Chapter 5: Fallacies. 23 February 2015

Transcription

1 Chapter 5: Fallacies 23 February 2015

2 Plan for today Talk a bit more about arguments notice that the function of arguments explains why there are lots of bad arguments Turn to the concept of fallacy and consider some examples

3 Arguments (review) The point of an argument is to give somebody a reason to believe its conclusion A good argument gives a reason by presenting, through its premises, evidence that the conclusion is true The premises present evidence if they are (recognizably) true, and their truth (recognizably) supports the truth of the conclusion.

4 Belief and inference Because you yourself are an intelligent person if you believe some statements PQR to be true, and if you recognize that the truth of PQR supports the truth of a statement C then you are likely to believe C already. Thus, belief is closed under evident entailment. E.g., You see that there are 100 people registered in A1 You see that are 99 people registered in A2-A5 So you also see that someone in A1 is not registered in A2-A5

5 Rational argumentation is hard Now, suppose Tony is trying to persuade you that C is true So Tony constructs an argument PQR, therefore C. Let s suppose that Tony s argument does give you a reason to believe C Tony needs to give you an argument for C because you don t just take his word for it. So then you surely can t take his word for PQR either But since PQR do present evidence for C, you must have already believed PQR before talking to Tony But since belief is closed under evident entailment, you re likely already to believe C yourself And of course, Tony cannot persuade you that C is true if you already believe it Therefore, it is almost impossible for someone to give you a good reason to believe something through argument

6 Objection: how about inferential skill? Reasoning can require effort and skill Everyone may fail to recognize that something follows from stuff we already accept A mathematician might discover it, though, and write it up Although mathematicians do discover things through reason... this is hardly ever the case with ordinary argumentation. When you re discovering that something follows from stuff you knew already... there s a characteristic feeling of mental strain That is not the feeling you get when you are reading an Op-Ed!

7 So why argue? Nonetheless, people do try to persuade each other Moreover, for that purpose they construct what look like arguments But if an argument can almost never give you a reason to believe something, then why bother with it?

8 The allure of argument People want to make sense of things Reasons help them do it So people have a desire for reasons So people are willing to accept as a reason what merely looks like one

9 Fallacies

10 Fallacious arguments An argument which only seems to present a reason is said to be fallacious Because people have a desire for reasons... fallacious arguments can be persuasive Indeed, people often commit fallacies when trying to make sense of things for themselves

11 An example There s no way Brian Williams misremembered. I was shot down once, and when something like that happens to you, you don t forget it.

12 What is a fallacy? In a fallacious argument, something seems to present a reason but really doesn t Thus, fallacious arguments involve illusions Just as there are typical kinds of optical illusions, so there typical kinds of illusions in argument A fallacy is a typical kind of argumentative illusion We ll spend the rest of the week going through well-known fallacies

13 Equivocation To equivocate is to slide between different meanings of the same word. E.g., You promised you would shovel the sidewalks I just meant the sidewalks on your property Do women need to worry about man-eating sharks?

14 Equivocation as a fallacy Often, the validity of an argument depends on a word s being used with the same meaning: E.g., All Fs are Gs, and all Gs are Hs, so all Fs are Hs Here, it must be the same G both times! An argument contains a fallacy of equivocation occurs when the validity of the argument depends on a word s being used univocally while the word is actually being used equivocally

15 Equivocation: example 1 Criminal actions are illegal, and all murder trials are criminal actions, thus all murder trials are illegal.

16 Equivocation: example 2 Everyone agrees that a fetus is human, and all humans have a right to life.

17 Eauivocation: example 3 Margarine is better than nothing. Nothing is better than butter. Therefore, margarine is better than butter.

18 Begging the question Begging the question means presupposing the claim in question When somebody makes an argument, the point is to persuade you that C is true In that case, C cannot itself be among the premises It is very common that the conclusion appears among the premises of the argument Of course, the conclusion will be a premise which is left implicit

19 Begging the question: example 1 Why do you believe that God exists? The Bible says so. But why do you take the Bible s word for anything? Because it is the word of God.

20 Begging the question: example 2 It is surely wrong to use federal funds to indulge the sexual appetites of foreign government officials. Even the Washington Times denounced this misappropriation of funds.

21 Begging the question: example 3 Do you still cheat on your taxes? Either way, you ve done something wrong, and you ll be punished for it.

22 Begging the question: example 3 Do you still cheat on your taxes? Either way, you ve done something wrong, and you ll be punished for it. Note in this case that what is presupposed is not the conclusion itself, but an intermediate step. More generally, an argument can beg the question by assuming something which is at least as controversial as its conclusion

23 Begging the question some further notes 1. You might think that fallacious arguments cannot be valid But actually, an argument that begs the question is guaranteed to be valid After all, it has the form PQR, therefore Q And it is impossible for an argument with those premises to have a false conclusion. The problem is rather that the premises are made to look antecedently acceptable when they aren t 2. Sometimes people use begging the question to mean making me curious Please don t.