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Finding Premises and Conclusions It’s one thing for your mom or your teacher to cut your arguments up
into little pieces for you, and draw a nice line between the premises and
the conclusion; it’s another thing entirely to catch arguments in the wild,
and dissect them yourself. In real life there’s usually no little line
separating the parts of an argument. Plus, there’s often some extra
filler material throw in just to pretty it up. Plus, as we’ll see soon
enough, there are other complications. If you want to survive in this
world, you need to learn how to find arguments in their natural
environment,
and tell them from non-argument imposters, and gut and clean those arguments
all by yourself.Fortunately there are some useful skills for all this that you can add to your Logical bag of tricks. 1. Finding the Conclusion. For this there are a couple of good tricks. First, look for the conclusion in the most likely places. Conclusions don’t typically show up just anywhere in an argument. Considerations of order and conversational structure usually stick the conclusion either (i) at or near the beginning of the argument, or else (ii) at or near the end of the argument. This isn’t 100% guaranteed – we’ll see some weird little arguments where the conclusion is wedged between two premises – but it’s still a pretty reliable rule of thumb. Consider Argument (2) yet again: (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. Notice how the conclusion comes at the end of the passage? A likely place for a conclusion. I could have made a variation on (2) instead: (2B)
You owe me $20. After all, I loaned you $10 last Friday; I loaned you $10 more on Saturday; and you haven’t paid any of it back. Here I didn’t carve it up for you, with a little line and all. It’s still pretty clear, though, that the conclusion of (2B) is “You owe me $20,” just like in (2). But now the conclusion comes at the beginning of the passage – another likely place for a conclusion. And there’s an even better second clue for finding the conclusion of an argument: conclusions often get marked as conclusions by special words and phrases whose only purpose in life is to point out what the conclusion is. For obvious reasons, I call such words and phrases conclusion markers. In (2), the conclusion sentence started with the word “so”. “So” is a classic conclusion marker: it’s only there to point out that what follows is the conclusion. Conclusion markers are just a convenience – they don’t add anything new to the conclusion, and we can get by without them. (In (2B), for instance, the conclusion sentence didn’t have “so,” or any other conclusion marker; still, we could figure out what the conclusion was.) Here is a list of some favorite conclusion markers: Conclusion Markers:
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Therefore Thus So Hence Consequently In conclusion We conclude (that) |
It follows (that) Shows (that) Proves (that) Indicates (that) Demonstrates (that) For these reasons, we see (that) Modal Phrases (must, have to) |
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Any of these would provide natural variations on the conclusion in (2): I could have said “Therefore, you owe me $20,” “Thus, you owe me $20,” “Hence, you owe me $20,” and so on. |
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A Little Something on Modal Phrases
You noticed in that list of conclusion markers that I had modal phrases at the end; and now you’re wondering just what modal phrases are, and how they mark the conclusion.
Here’s how it works: modal phrases are phrases that talk about how things could possibly be, or must necessarily be – as opposed to just plain how they are. Modal phrases include: possible, possibly, may, maybe, might, can, could, necessary, necessarily, must, have to – and others I can’t think of right now. In particular, it’s those last couple of phrases – must and have to – that act as conclusion markers. So we could make an argument like this: (4) John is either at the pub, or at the football match. But since the football match ended hours ago, John must be at the pub. I didn’t clean this one up for you, and draw the
pretty line. But it’s not that hard – the only real trick is noticing
that the second sentence contains both a premise and the conclusion.
Cleaned up some, the argument would read:
(4) (Cleaned Up Some) John is either at the pub, or at the football match. The football match ended hours ago. ____________________________________ John must be at the pub. Actually, the word “must” is just a conclusion
marker: it’s not a core part of the conclusion, just a road-sign pointing
to the conclusion. It isn’t a question of whether John must
be at the pub, but whether John actually is. Really, the fully
cleaned-up version of this argument would strip out the “must,” like
so:
(4) (Cleaned Up Some More) John is either at the pub, or at the football match. The football match ended hours ago. ____________________________________ John is at the pub. But beware: modal terms lead many different lives,
and only in some of those lives do they mark conclusions. Sometimes
they talk about how things (and people) are obliged to be, as in the following
devious variation on (4):
(4B) Everyone must be at their place of business for the town inspection. John owns and operates the pub. _________________________________ (So) John must be at the pub. Now the “must” means something like “is obliged to”. Here “must” is not a conclusion marker at all – it really is a part of the conclusion.
Looks tricky, right? So finally, in response to this trickiness, here’s a mini-test as to whether the “must” is acting like a conclusion marker, or saying something else (like obligation). When you see a “must” in the middle of a sentence, ask: can it be replaced by “It must be that,” at the beginning of the sentence, and still mean the same thing? If must can be replaced by it must be that, then odds are the “must” was just a conclusion marker. Try it with our must-sentence, “John must be at the pub”. When reworded, we get: It must be that John is at the pub. Now, that’s a pretty good rewording of the conclusion in Argument (4) – showing
that the “must” in Argument (4) was likely just a conclusion marker.
But notice how it’s a really bad rewording of the conclusion in Argument (4B). The conclusion in (4B) was saying that John was obliged to be at the pub – showing us that in (4B), the “must” was not acting like a conclusion marker.
It may not be a perfect test, but at least it’s something. |
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2. Finding the Premise(s). What works for the conclusion, works as well for the premises: premises have a classic set of phrases that come right before them, marking them as premises. As you’ve probably already guessed, I call these phrases premise markers. Here is a list of some classic premise markers: Premises Markers:
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Since
Because For Follows from May be inferred from May be deduced from |
As shown by
As indicated by On the grounds that For the reason that After all |
| These are all the tools in our Logical Bag of Tricks so
far; but they’re plenty for just dissecting arguments. Between tricks
for finding the conclusion, and tricks for finding the premises, you can
generally carve up an argument pretty easily.
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next: "combo" sentences
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