Arguments

1. An argument is a set of propositions (represented by sentences) that justify (imply, lead to) a conclusion that the giver of the argument wants its recipient to believe.

2. Example:

Howard Dean wants you to believe he’d be a responsible President. So he might say:

[Premise 1]: People who were responsible Governors make responsible Presidents.

[Premise 2]: I was a responsible Governor.

[Conclusion]: Therefore I would be a responsible President.

Notice that you can’t accept both premises as true and still deny the conclusion. The conclusion is justified by (follows from) the premises. If you believe the premises you should believe the conclusion.

3. So, if you want to dispute the argument, you need to find something wrong with one of the premises. You could counter-argue either by giving reasons for thinking that a person’s conduct as Governor isn’t reliable evidence about their probable conduct as President, or you could give reasons for doubting that Dean was a responsible Governor as claimed, or both.

4. We distinguish between two general properties of arguments: soundness and validity. To justify a conclusion (make it convincing), an argument must be both valid and sound.

5. An argument is valid if the conclusion follows from the premises, regardless of whether the premises are true or justified. For example:

[Premise 1] All pigs can fly.

[Premise 2] Arnold is a pig.

[Conclusion] Therefore Arnold can fly.

If these premises were true or justified, then the conclusion would be justified. So the argument is valid. However, it isn’t sound: one of the premises (#1) is false.

6. An argument is sound if it is valid and all its premises are justified. So, for example:

[Premise 1]: The newest city in Alabama isn’t its capital.

[Premise 2]: Birmingham is the newest city in Alabama

[Conclusion]: Therefore Birmingham isn’t Alabama’s capital.

This argument is valid, because its conclusion is justified by its premises. And both of its premises are justified. Therefore, it’s sound. You should believe its conclusion.

7. An argument is invalid if its conclusion doesn’t follow from its premises. In this case, it’s unsound regardless of whether the premises are true.

Example:

[Premise 1]: Michael Jackson is an odd person.

[Premise 2]: Child molesters are odd people.

[Conclusion]: Therefore Michael Jackson is guilty of child molestation.

The premises here are both justified. However, the argument is invalid because its conclusion doesn’t follow from its premises. For the conclusion to follow from premises on these two topics, one of them would have to say that all odd people are child molesters. But no premise says this. Therefore, the conclusion is unjustified (doesn’t follow from the premises).

Notice here that the conclusion might be true. But even that wouldn’t make the argument valid. Even if Michael Jackson is guilty, this argument gives you no reason to believe it.

8. Q: What makes a premise justified? A: A justified premise should itself be the conclusion of a sound and valid argument.

9. This means that you can always question an argument, if it’s valid, by asking for the justifications for its premises. Doesn’t this imply that any argument can be questioned forever? Each argument will need a back-up argument for its premises. This back-up argument will itself have premises. So can’t you then always go on to ask for the arguments for those premises?

10. Yes, actually. But for practical purposes we stop we reach an argument that has no controversial premises.

11. How do you know when a premise is controversial? There’s no mechanical rule for this. You have to rely on your wider knowledge of what the world is like. But you can reasonably expect to persuade somebody that a conclusion is justified if you can give them an argument that doesn’t depend on any premises they regard as controversial. Thus, for example, a Christian might be able to persuade another Christian of something using fewer arguments than she’d need to persuade an atheist of the same thing, because fewer premises would be viewed as controversial by either party in the first case.

12. In philosophy, we’re usually interested in finding arguments that would persuade anybody. Therefore, we need to try to justify our conclusions back to premises that nobody (at least, nobody who’s not crazy) would regard as controversial. Thus in philosophy we don’t take much for granted. This is not, then, because philosophers are people who don’t believe anything. It’s because philosophers are trying to find general arguments that will work in as many contexts as possible.

13. People don’t usually spell out their arguments explicitly into premises and conclusions as we’ve been doing above. They just say stuff. When they’re trying to persuade you of something, you need to do some analysis to try to find and construct the underlying argument they’re trying to use. This is often the hardest part – by far! – of settling issues, questions and disagreements. But there’s no way around the need to do it. If you’re not willing to do this work, then … I have a lot of useless stuff I’d like to sell you!

14. Putting all this together:

When somebody tries to persuade you of something, here are the steps you need to follow in deciding whether to believe them:

(i) Analyze what they say to try to figure out what their underlying argument is. It’s usually not too hard to figure out the intended conclusion. But what are the premises?

(ii) Is the argument valid? If no, don’t be persuaded. If yes, go to step (iii).

(iii) Are the premises controversial to you? Are the premises controversial to others? If they’re uncontroversial to you but controversial to others, why do these others find them controversial? Maybe the others have good reasons, and you should think again about your own view before accepting the conclusion. If the premises are controversial to you – on either first or second thought – go to step (iv).

(iv) Ask for new arguments for all controversial premises.

(v) Repeat (i) – (iv) until either:

(a) The would-be persuader can’t find a valid argument for one of the premises she needs. Then don’t accept the conclusion. (This doesn’t mean rejecting it; you might just consider it unsettled.)

or

(b) All premises that have been produced at every step are uncontroversial, and all arguments that have been given are valid. Accept the conclusion. Congratulations: you have a brand new belief!