Basic Concepts: Arguements

As my first contribution to the growing list of basic terms and concepts, I'm going to explain a few things no one asked about when I opened the request line. But, these are ideas that are crucial building blocks for things people actually did ask about, like falsifiability and critical thinking, so there will be a payoff here.

reposted from: Adventures in Ethics & Science
my highlights / edits

Philosophers talk a lot about arguments. What do they mean?

An argument is a set of claims. One of those claims is the conclusion which the other claims are supposed to support. While logicians, geometers, and that crowd customarily give you the conclusion as the last claim in the argument, arguments in novels and op-ed pieces may give you the conclusion at the very start of the argument.

The non-conclusion claims in the argument are generally referred to as premises or assumptions. These claims are the reasons being offered to support the conclusion of the argument. Note that some of the claims labeled as "assumptions" feel like certainties.

The point of an argument is to give good reasons for accepting the conclusion. An argument is something stronger and more persuasive than a mere opinion. What makes an argument more persuasive is that it makes its assumptions clear and then shows how these assumptions lead logically to the conclusion.

A valid argument is one where the truth of the premises guarantees the truth of the conclusion. In other words, if your argument is valid, someone who accepts your premises as true will have to accept your conclusion or else embrace a logical contradiction.

Do you like Ps and Qs (and upside down As and backward Es)? If so, you'll find a wide selection of symbolic logic textbooks that set out a dizzying array of valid patterns of inference. Many philosophers manage to set out arguments without talking in Ps and Qs and upside down As and backward Es, though. There are some patterns of inference that careful thinkers will recognize as valid (even if they can't whip out the old school name of the syllogism) and others that they will recognize as not guaranteeing a true conclusion even if the premises are true.

Here's an example of an invalid argument:

1. If my battery is dead, my car won't start. (premise)
2. My car won't start. (premise)
3. Thus, my battery must be dead. (conclusion)

It's perfectly possible for both premises to be true, yet for the conclusion to be false (because something else is wrong with my car that is keeping it from starting). In other words, we shouldn't take (1) and (2) as sufficient reasons for accepting (3).

Here's an example of a valid argument:

1. Britney Spears is from Mars. (premise)
2. Martians have astounding vocal range and are great dancers. (premise)
3. Hence, Britney Spears has astounding vocal range and is a great dancer. (conclusion)

If claims (1) and (2) were true here, there is no way that claim (3) could fail to be true. Accepting the assumptions commits you to the conclusion -- unless, of course, you choose to opt out of the shared rules of valid inference we've been trained to accept. That's always an option, but it's not one that puts you in a very good place to engage with others who accept those rules (which is something you'd want to do to persuade them to accept some of your conclusions)!

Valid or not, most of you are not accepting my argument's conclusion, that Britney Spears has astounding vocal range and is a great dancer. Why not? Perhaps because you reject my premise that Britney Spears is from Mars and/or my premise that Martians have astounding vocal range and are great dancers. Even if the logical connections between my premises and my conclusion are good, if any of my assumptions are false, you're entitled to reject my argument as giving good reasons to believe the conclusion. (By the way, even people who accept the truth of the claim that Britney Spears has astounding vocal range and is a great dancer will reject the argument offered here in favor of that conclusion -- they won't want to endorse the false premises about Martians.)

An argument that is valid and whose premises are true is a sound argument. Not only does it have the right kind of logical connections between the conclusion and the reasons offered to support the conclusion, but all those reasons are true claims. The challenge, of course, is in being sure of the truth of your premises. "All men are mortal" sure sounds like a true claim, but given that there are scads of people who haven't yet demonstrated their mortality by kicking off, can we be certain that one of them won't turn out to be immortal?

Don't go whipping out data on all the humans who have dies so far, thus proving themselves to be mortal and making it a good bet that we are all mortal, too. The argument:

1. Guy 1 died.
2. Guy 2 died.
3. Guy 3 died.
4. Guy 4 died.
5. Guy 5 died. ...

Thus, we're all going to die eventually.

looks like an appealing argument, but it is not a valid argument -- at least, there's no guarantee that the truth of the conclusion follows from the truth of the premises. Rather than being a deductive argument, it's an inductive argument.

Inductive inference can be plenty useful, but as any broker -- or any kid who plays a lot of Duck Duck Goose -- will tell you, there is a real danger in inferring future outcomes from past performance. More about this when we take up "falsifiability".