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Arguments It will come as no surprise to you that Logic studies arguments. In particular, Logic aims to evaluate
arguments, to tell whether an argument is good or bad. We will soon
enough set about separating good arguments from bad ones; but before we can
even begin making those value judgments, we need to get clear on what we’re
judging. So our first question is a simple descriptive one: what is an argument?Consider Passages (1) and (2): |
| (1) You owe me $20. |
(2) I loaned you $10 last Friday. I loaned you $10 more last Saturday. You haven’t paid any of it back. -------------------------------------------- So, you owe me $20. |
| Obviously the two passages have something in common: if I say either of these
things to you (and I’m serious about it), I’m trying to get into your head
the idea that you do owe me $20 – to get you to believe this. But they go
about this in different ways. (1) simply states: You owe me twenty dollars.
Here, I’m just claiming this; either you believe me or you don’t, and that’s
that. If (1) does the trick, and you take my word for it, then I’ve succeeded;
otherwise I’m out of luck.
On the other hand, (2) doesn’t just ask you to take my word for it that you owe me $20. It tries to give reasons why you should believe this; it backs up the claim with some evidence. (I’ve conveniently drawn a line between the evidence, and the claim it’s evidence for.) Maybe that evidence is reliable, or maybe it’s not, but that’s a worry about evaluation we can put off for later. The point right now is that (2) doesn’t just make a claim out of the blue, and ask you to believe it, (2) also gives some reason to believe it. (1) is just a claim. (2) is an argument. We set about drawing some useful morals from these simple examples. 1. One consequence is clear already: in an argument, we expect to find two parts: (1) something the speaker wants us to believe, and (2) some reasons the speaker gives for believing it. In Logic we have names for these two essential parts of an argument. The claim the speaker wants us to believe is called the conclusion. The reasons the argument offers for believing the conclusion go by many different names: the reasons, the evidence, the grounds. But nobody ever got rich using such ordinary words, so we’ll coin a special technical term for these supporting claims: in Logic they’re called the premises. Every argument has to be arguing for something; and to be an argument (instead of a mere claim) it needs to offer reasons why we should believe that something. So clearly:
Every argument has a conclusion, and one or more premises.
2. Another point is even more obvious: (2) is a string of four sentences. You don’t typically find dollar bills and calendars and apples and shoes in arguments (though you could find claims about all these things) – you find sentences. Indeed, every argument we look at will be just a string of sentences. Of course being a string of sentences isn’t all there is to being an argument. (After all, (1) is a string of sentences too – just a very short, one-sentence-long string of sentences.) But even if this point isn’t the whole story about arguments, it’s useful enough to mention:
Every argument is a string of sentences.
We can even tweak this a little, and say what kind of sentences make up an argument. The conclusion is what the arguer wants you to believe – believe to be true. And for the premises to work their magic on you, you have to believe them – believe them to be true. So all the sentences in an argument have to be the kind of sentences that can be true. We call such sentences declarative sentences. Declarative sentences are sentences that can be true or false – as opposed to commands or questions, which can’t be true or false. (“Close the door!” – true or false? It doesn’t make any sense to ask that, right? Because a command isn’t the kind of sentence that can be true or false. It’s not declarative.) Every sentence in an argument has to be a declarative sentence. Now admittedly, sometimes an argument can contain, say, a question in it – but even then the question itself won’t be a premise or conclusion. Consider (3):
(3)
If you want to pass logic, you should study. Now, do you want to pass logic, or fail it? ------------------------------------------- OK, then -- clearly, you should study. (3) is arguing that you should study. And there is a question in there, masquerading as a second premise. But that question is only there to point out its obvious answer: you want to pass logic. It’s the (unspoken but obvious) answer that’s doing the work in this argument, and that answer is a declarative sentence. The question is only there to point it out. Even here, all the premises and the conclusion are declarative sentences. So we tweak our earlier claim a little bit:
Every argument is a string of declarative sentences.
3. Finally, notice something about what an argument does. Both (1) and (2), for example, try to get you to believe that you owe me $20. But with (1) the speaker just has to hope you believe it; whereas in (2), the speaker uses premises to bring you to believe it, to cause you to believe it. Using reasons to cause someone to believe something is called convincing. (2) tries to convince you that you owe me $20; (1) just throws out the claim, hoping you’ll buy it. Since every argument is providing reasons (good or bad) for believing some conclusion, every argument is intended to convince someone (the audience) of something (the conclusion).
Arguments are intended to convince someone of something.
Now I admit, in Logic we do sometimes build arguments in a vacuum, just to study them, and not really with any hope of convincing someone of something. Still, the real purpose of arguments is to convince people in everyday life. (By the same token, we sometimes buy a new car only to fill it with dummies and crash it in a lab; but still, the real purpose of cars is to carry people and their things around in everyday life.) Putting these points together, we get a nice working definition of an argument: |
| An argument is a string of declarative sentences intended to convince someone of something. |
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When you read a string of sentences – like (1) or (2) – you can quickly decide
if it is an argument, or just a (non-argumentative) string of sentences,
by asking: is it trying to convince me of something? If it is, there will
be a claim being set out (the conclusion) and also some evidence for that
claim (the premises) meant to convince you of that claim. |