Identifying and Reconstructing Arguments

Identifying Arguments• Arguments have two parts, premises and

conclusions. It’s easiest to identify a conclusion first. If you’ve got a passage you think might contain an argument, try to determine just what it is that you’re supposed to be convinced of. Then try to determine why the author (or speaker) thinks you ought to be convinced.

• If that method fails then look for indicator words. Words like ‘since’ and ‘because’ suggest that a premise follows. Words like ‘hence’ and ‘therefore’ suggest that a conclusion follows.

Examples

• Alan won’t reveal a third year of tax information. He must be hiding something shady.

• Barb is not an American citizen since she has not revealed a third birth certificate.

• Charlie believes that the state should intervene in cases of market failure. Thus, since all adherents of government intervention are socialists, Charlie is a socialist.

Caution

Relying exclusively on indicator words can sometimes lead you astray. Consider the following examples:

• He fell because he tripped.• He tripped because he fell.• The price has fallen since the company

insiders sold their stake.• He couldn’t get a loan since he’d had a short

sale within the last seven years.

Reconstructing Arguments

• An argument in standard form is one with the premises above a line and the conclusion below a line. For an example consider the third argument on slide three in standard form.1. Charlie believes that the state should intervene

in cases of market failure.2. All adherents of government intervention are

socialists.3. So, Charlie is a socialist.

Extended Arguments

Some arguments have premises for which evidence has been offered. For example:

A short sale is as bad for your credit score as a foreclosure. Anyone with a foreclosure will have a low credit score for years. So, anyone with a short sale will have a low credit score for years. Since Bob just completed a short sale of his house, he’ll have a low credit score for years.

Notice that at least one sentence is both a premise and a conclusion.

The example in Standard Form

1. A Short sale is as bad for your credit score as a foreclosure.

2. Anyone with a foreclosure will have a low credit score for years.

3. So, anyone with a short sale will have a low credit score for years.

4. Bob Just completed a short sale of his house.5. So, Bob will have low credit score for years.

Two Flaws

• There are only two possible flaws of an argument: a false premise, and bad form.

• Contrast these two arguments:1. All reptiles are green.2. Bernie Madoff is a reptile.3. So, Bernie Madoff is green.

1. Iraq borders Syria2. So, The Hague is in the Netherlands

Missing Premises

• Sometimes premises (or conclusions) are unstated. This might be because they are too obvious to include or because they are assumptions that are unrealized even to the argument’s author.

• When reconstructing arguments you should fill in the missing premises, but if they are unstated, how do you know what they are?

• There are two rules to follow when adding premises:

Charity and Faithfulness

• Charity: You should make the argument as good as possible. Give the argument the best form possible while giving it only true premises.

• Faithfulness: You should present the argument that the author intended to give.

• What if the author didn’t intend to give the best possible argument? That is, what if the rules conflict?

Examples

• Iguanas are cold-blooded because they are reptiles.

• That person’s name is ‘Charlie’ so that person is male.

• Richard Nixon says “You can trust people who aren’t crooks, so you can trust me.”

• I was trying my best; and if you’re not cheating, you’re not trying.