Section Progress:

3.1  Identifying Arguments

Let's return to our detective story. You solved your first case. Thanks to you, Quinn is behind bars.

But instead of an award, the Sergeant put you on paperwork all afternoon.

As you exit the building that evening, you realize you haven't left the office in 36 hours.

"Psst!"

You're not sure if you heard something or if it's the sleep deprivation talking.

"Hey you."

You look toward the sound and see a figure in the shadows. A hand waves you over.

"I'm off duty," you say, dreaming of bed. "Take it up at the station."

"I just thought you'd like to know," the voice says, "there was false evidence in that file."

There was false evidence in the file.

You freeze. You start to feel queasy, and you don't think it was the leftover pizza you had to eat for breakfast.

You take a step toward the shadow and see that it's Raquel. She must have been released this morning.

"How do you know that?" you demand, a bit defensively.

Because Quinn is innocent.

"Because Quinn's innocent," she says.

You don't want to believe it, but that queasy feeling gets stronger.

Raquel is making an argument here, though it's a bit harder to evaluate than the arguments we've already seen.

First, let's see if we can identify what her argument is. Here's her claim: "There was false evidence in the file, because Quinn is innocent."

Identifying arguments can be surprisingly difficult, so let's see how to master this skill.

You are already familiar with arguments. An argument in logic isn't two people yelling at each other. It is a collection of sentences, one of which (the conclusion)  is supposed to follow from the others (the premises).

Argument: a set of premises and a conclusion.

When someone makes an argument, they often use signal words that indicate what the premises or conclusion are.

For example:

Signal words come in two varieties: they are either premise signals or conclusion signals.

Premise signals: words that indicate a premise. "Because", "since", "for", "given".
Conclusion signals: words that indicate a conclusion. "Thus", "so", "hence", "therefore".

"Because" is a premise signal: it indicates a premise, a reason or grounds for thinking that the conclusion is true.

Other premise signals are "since", "for", and "given". Common conclusion signals are "therefore", "so", and "hence".

If we pay attention to the signals, it is easier to identify an argument correctly.

Let's practice.

Kierkegaard didn't have the happiest personal life, which you could probably have guessed.

Now let's make sure you know what each of these words is signaling. Sort all the words according to whether they are premise or conclusion signals.

If you are having trouble, imagine using each word in an argument to see what role it plays.

Not every argument will use signal words, but there's also a way to figure out the cases that don't. Just rephrase the argument in your head with signal words and see if it captures the author's intent. If it does, then you can now identify the premises and conclusion.

Once we know about signals, we can tell Raquel is arguing this:

1. Quinn is innocent.
So:
2. There was false evidence in the file.

Next we need to assess her reasoning.

3.1 Identifying Arguments