So far, I’ve talked about clarifying the language and structure of arguments, as a first step in evaluating them. But how do we take the next step, and actually consider whether they’re good or bad arguments? And what even makes an argument a good one?
The short answer is that a good argument has premises that adequately support its conclusion. How? By meeting three criteria: they need to be acceptable, relevant, and sufficient. The resulting abbreviation, ARS, sounds a little too much like the British word “arse” to some people, so sometimes you’ll see it shuffled to spell RAS, or ARG (by changing “sufficient” to “sufficient Grounds”). But I say damn the torpedoes. Let’s keep ARS, and remember this: when you’re making a good argument, you’re covering your ARS.
Are the Premises Acceptable?
Truth and Plausibility
The most complex of the ARS criteria is acceptability, because there are several ways to judge the acceptability of premises. The first thing is that acceptable premises are true, or at least plausible--they can be provisionally accepted for the purposes of the argument. If they aren’t true or plausible, then they can’t support the conclusion, and thus aren’t acceptable. Here's an example:
P1: No mammal lays eggs.
P2: Platypuses lay eggs.
___________________________
C: Therefore, platypuses are not mammals.
That would be a good argument, except that the first premise is false: some mammals (platypuses and echidnas) do lay eggs. Obviously, a premise can’t be acceptable if it’s false.
But then, how do we know which premises are true and which are false? That’s the big question, and there are no easy answers. Some philosophical skeptics claim there’s little or nothing we can know for sure. We might say we know something is true because we saw it with our own eyes, but we’ve seen how error-prone perception and memory can be. People in prehistory could have argued that the earth is flat because they can see with their own eyes that it’s flat. But the earth isn’t flat. Perception can be limited and deceiving, so seeing something with your own eyes doesn’t mean you see it accurately.
Another problem that extreme skeptics point to is the infinite regress of premises, sometimes called the skeptical regress. We might say a premise is true if it’s supported by other true premises, but then, how do we know those premises are true? If we say that they’re supported, in turn, by other true premises, then where does the chain of premises end? Consider the following dialogue:
Jill: “Some mammals lay eggs, because platypuses are mammals, and they lay eggs.”
Lil: “How do you know platypuses lay eggs? Have you ever seen it happen?”
Jill: “No, but I’ve read it in books written by other people who have seen it. It’s well-documented that platypuses lay eggs.”
Lil: “Then how do you know the people writing the books aren’t lying?”
Jill. “Because I don’t know of any reason why they would lie.”
Lil: “How do you know there aren’t reasons you haven’t thought of? What if platypuses are a hoax?”
Jill: “......”
This line of questioning could go on forever, if Lil refuses to accept any of Jill’s premises. And to some extent, Lil does have a point. Everything Jill knows about platypuses is secondhand. And that’s true for all of us--if not about platypuses, then about other things. Most of what we think we know is secondhand. We didn’t see it ourselves, so we’re taking people’s word for it. I didn’t see dinosaurs walk the earth, or watch the battle of Waterloo. I’ve never seen Greenland with my own eyes, and I’ve never seen a platypus in real life. But does that make it unreasonable for me to believe in all these things? No, because it’s much more plausible that they exist than that they’re elaborate, centuries-long hoaxes. The same argument about plausibility could be made to someone who says that perception is fallible. Yes, perception is fallible, but it’s not THAT fallible. Yes, it’s conceivable that we all live in the Matrix, and all our experiences have just been images piped into our brains, but it’s not at all likely.
So, while the extreme skeptics are right that there’s little we can know for absolute certain, it’s a mistake to think we need absolute certainty to accept premises as true. Unless we’re talking about things that are true by definition (”No bachelor is married”) or logical necessity, (Platypuses either exist or don’t exist”) then when we say something is true, that just means it’s extremely likely to be true.
So how do we know what’s extremely likely to be true? There are a few ways. If we see a thing happen with our own eyes, and it’s not wildly at odds with our normal experience, that’s a reason to think it’s probably true. If I see someone walking a dog down the street, there’s no reason to think my eyes deceived me. On the other hand, if I see someone walking a miniature horse down the street, I might want to look twice. It wouldn’t hurt to check to see if other people saw it, too, or if someone had taken a picture of the horse. The more we try to verify our direct perceptions, the more likely they are to be true. That still doesn’t make them certain, because some illusions are very persistent, and look the same to most people. The earth looks flat to everyone walking on it, even though it isn’t. Still, lots of things we experience firsthand are perfectly plausible, and there’s no particular reason to doubt them. I could speculate that I’m laying in bed dreaming right now, and not really sitting here typing, but what’s most likely is that I’m sitting here typing.
Testimony
But what about all those things we don’t see with our own eyes? What about when we need to rely on the testimony of others? After all, that’s something we have to do every day. If I watch the news, check the weather forecast, read a history book, or hear that platypuses lay eggs, I’m relying on testimony. Luckily, there are several ways of judging the plausibility of testimony. First, it’s more plausible if it fits with our ordinary experience: If the weather report says a snowstorm is bearing down on Denver in January, that’s plausible. If it says a hurricane is coming, that isn’t plausible. A person’s claims are also more plausible if they don’t conflict with other claims they’re making. If a coworker tells you they were out sick yesterday, that seems pretty plausible…unless you hear them telling someone else they went skiing. Testimony is also more plausible if the person giving it has always been trustworthy in the past, and doesn’t have conflicts of interest that might tempt them to bend the truth. If your coworker who lied about being sick calls in sick again, you have good reason to be suspicious. If a car salesman says you won’t get a better deal anywhere, you have reason to take that with a grain of salt, because he has an interest in telling you that car. That doesn’t necessarily mean he’s lying, of course. It just means his claims need extra scrutiny.
What about the testimony of experts, like doctors, scientists, and economists? Let’s stick a pin in that question, and come back to it in a later post about arguments from authority.
Other Unacceptables: Unclarity, Contradiction, and Presumption
Premises are also unacceptable if they’re too vague or ambiguous for us to judge whether they’re true, or even what they mean. I could make the claim that free will exists, and base it on a premise that says something like, “The will exists in four-dimensional quantum potentiality beyond time and space”. But what does that even mean? Nothing, because I just made it up. Such pseudoprofundity is common and impresses many people, but it’s often more or less meaningless, and can’t be taken as an acceptable premise. Premises are also unacceptable if they conflict with each other, or if they presume the truth of the conclusion they’re supposed to be supporting, as persuasive definitions and other circular arguments do.
Premises About Values
Oftentimes premises make claims about values, not facts. If I argue that bloodsports like dogfighting are morally wrong, and support it with the premise, “It is wrong to inflict suffering on animals for entertainment”, that premise isn’t an empirical fact. You can’t measure wrongness in a laboratory. Does that mean it’s unacceptable or meaningless, or that dogfighting is morally right? Of course not. There are very good reasons for thinking dogfighting is ethically atrocious, but the reasons aren’t all things that can be grounded in fact. That makes judging premises (and whole arguments) about values and ethics unusually difficult. But it’s also extremely important. Most people will find the premise above acceptable--perhaps even true--even though it’s not an empirical fact. It’s a reasonable premise that we can start to build an argument on. We can’t prove it in a lab, but we can’t write it off as meaningless or unimportant, either. It would be nice to have more certainty than that, but sometimes we have to do the best we can.
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