Placeholder Image

字幕表 動画を再生する

  • Crash Course Philosophy is brought to you by Squarespace.

  • Squarespace: Share your passion with the world.

  • How do you know that aspirin will take care of your headache?

  • Why do you really want to see the new Marvel movie, even though you haven’t heard anything about it, good or bad?

  • Your ability to do things like predict how a medication will affect you, or what movie

  • you might like, or even things like what the perfect gift might be for your best friend,

  • or what’s the fastest way to get to campus –- all of this stuff, you know through induction.

  • Deductive arguments are great because they give us certain answers.

  • But unfortunately, much of the world cannot be summed up in a neat deductive proof.

  • Deduction requires a fair amount of general information to give you a specific conclusion

  • that is, frankly, probably kind of obvious.

  • So, philosophy -- and basically, you know, life as well -- require that you have other ways of reasoning.

  • In addition to knowing how one fact leads to another, you also need to take what youve

  • experienced before, and use that to predict what might happen in the future.

  • And you need to be able to rule out what can’t be true, so you can focus on what can.

  • Through these kinds of reasoning, youre not only able to figure out stuff like how

  • to fix your headache, and why your roommate might be acting weird. You can also come up

  • with better, more skillful argumentsand counterargumentswhich are some of the

  • most important maneuvers in the philosophical game.

  • And maybe the best part is, you already know how to use these techniques.

  • In fact, I bet youve used them this very day. You know this!

  • [Theme Music]

  • If you possess any ability to really predict the future, it lies in your ability to reason inductively.

  • Inductive reasoning relies on the predictability of nature to reveal that the future is likely

  • to resemble the past, often in important ways.

  • For example, there’s tons of research to support the knowledge that aspirin -- acetylsalicylic

  • acid -- is an effective treatment for pain, like headaches.

  • And you probably have personal experience with the effects of aspirin, too.

  • So, you believe that this aspirin tablet will cure the headache you have right now, because

  • countless aspirin tablets have cured countless headaches in the past.

  • Likewise, you want to see the new Marvel movie, because you liked most of the other ones,

  • so you believe that theyll continue to deliver for you, entertainment-wise.

  • But it’s important to remember that, unlike deduction, where true premises entail true

  • conclusions, inductive premises only mean that the conclusion is likely to be true.

  • Inductive arguments don’t provide you with certainty. Instead, they work in terms of probabilities.

  • And theyre useful for more than predicting what’s going to happen. For example:

  • Most men in ancient Athens had beards. Socrates was a man who lived in ancient Athens.

  • Therefore, Socrates probably had a beard

  • This is an inductive argument, because it starts with what we already knowabout

  • the grooming habits of ancient Athenian men, and about the time and place in which Socrates

  • livedand makes an educated guess based on that information.

  • There’s no guarantee that the conclusion is correct, but what’s known would seem to support it.

  • Reasoning like this is incredibly useful, which is why it’s so common. But there’s also a problem.

  • The future doesn’t always resemble the past. And every pattern has its outliers.

  • So induction always has the potential to produce false results. Aspirin might not work on a

  • really bad headache. The new Marvel movie might be awful. And, yeah, maybe a specific

  • guy in Athens had a beard but it’s possible he didn’t!

  • While the world tends to work according to predictable rules, sometimes those rules are violated.

  • And you know what you need when that happens? A little Flash Philosophy. Off to the Thought Bubble.

  • Contemporary American philosopher Nelson Goodman confronts the problems of induction, using

  • a thought exercise about a hypothetical substance called grue.

  • According to Goodman’s scenario, grue is anything that’s the color green before a

  • certain time, a time that we will call t.

  • And another property of grue is that, while it’s green before time t, it’s blue after it.

  • Now, let’s assume that were living in a time before t. T could happen a hundred

  • years from now or tomorrow, but we know that all of the emeralds weve ever seen are green

  • So, inductive reasoning lets us conclude that all emeralds are green, and will remain green

  • after time t -- since emeralds haven’t been known to change color.

  • BUT! All emeralds are grue! Because it's not yet time t, and they're green, which is part of the definition of grue.

  • So we have no choice but to conclude that the emeralds will be blue after time t arrives.

  • Now weve got a problem. Because inductive reasoning has led us to conclude that emeralds

  • will be blue after time t, but inductive reasoning also tells us that theyll remain green.

  • Goodman’s riddle reminds us that inductive evidence can be flawed, or contradictory.

  • It can make you think that you can predict the future, when of course you can’t.

  • So, there are times when you need to get at the truth in other ways. Like by eliminating

  • what’s obviously not true, and considering what’s most likely.

  • And for this, we turn our attention to one of the most important philosophical figures

  • of 19th century England: Sherlock Holmes.

  • In chapter six of Sir Arthur Conan Doyle’s “The Sign of the Four,” Mr. Holmes says, and I quote:

  • When you have eliminated the impossible, whatever remains, however improbable, must be the truth.”

  • This is probably the best, most succinct description ever given of the kind of reasoning known as abduction.

  • Which I know, it sounds like were talking about a kidnapping or something, but abduction

  • is a thought process sometimes described asinference to the best explanation.“

  • Abduction doesn’t reason straight from a premise to a conclusion, as weve seen in deduction and induction.

  • Instead, it reasons by ruling out possible explanations until youre left with the

  • most plausible one, given the evidence. Consider this:

  • Anna told you she failed her physics midterm.

  • Anna hasn’t been in physics class since your teacher graded the exams.

  • Anna has been in sociology class, which meets right after physics.

  • Anna dropped physics.

  • Now, with only these premises, we can’t deductively or inductively prove our conclusion

  • that she dropped physics.

  • But, it’s a justifiable conclusion, because, given what we know, dropping the class is

  • the most plausible explanation of events.

  • We know she’s not sickbecause she’s still going to sociologyand we know she

  • had good reason to withdraw from the class, because she was unlikely to pass.

  • Concluding that she dropped the course makes the most tidy use of our information, without

  • leaving any loose ends. So let’s look at another one:

  • You and your roommate ate sushi last night.

  • You both wake up with violent stomachaches.

  • You and your roommate ate some bad sushi.

  • The mere fact that youre both sick doesn’t prove that the sushi caused the sickness.

  • But, given that you both ate the same thing and you both have the same symptomsabsent

  • other information, like that a stomach virus is going around your dormthe best explanation

  • is that the sushi caused your intestinal anguish.

  • Now, like induction, abduction doesn’t give us certainty.

  • But it is a really useful way to get through puzzling situations when you don’t have

  • clear evidence from the past to help you out.

  • Doctors use abduction a lot when theyre diagnosing illnesses, and detectives of course

  • use it when piecing together evidence.

  • You probably use it pretty often toojust beware, because abduction must be used carefully!

  • It uses only information you have at hand -- that’s why doctors and detectives work

  • so hard to dig up more data, and re-create events from the past, so they can help draw better conclusions.

  • All right, now that weve looked at some argument types, let’s find out how philosophers

  • use arguments to interact with each other.

  • Because, philosophers don’t argue like other people do.

  • It’s not like the conversation you have around the dinner table about whether the

  • Patriots are better than the Seahawks, or why plain M&Ms are superior to peanut, which

  • is clearly a preposterous position to take.

  • Philosophers hold each other to different, higher standards.

  • They don’t teach each other get away with saying, “I reject your argument because

  • I don’t like its conclusion.” Or, “That’s preposterous, peanut M&Ms are so good.”

  • Instead, if you disagree with a conclusion, you need to give reasons, just like the first

  • person did when they made their case.

  • Both people involved in this kind of exchange are known as interlocutors, because we have

  • to name everything. The first one advances an argument, and the second one can either

  • accept it, or offer a counterargument, which is just what it sounds likean argument

  • offered in opposition to another argument.

  • Think back to Socrates and the beard.

  • You think Socrates had a beard, and your reasoning is that most men in his time and place had them.

  • I, however, think youre wrong. So I give you a counterargument.

  • Gorgias, a contemporary of Socrates, said Socrates couldn’t grow a beard and that

  • he would sneak into barbershops and steal discarded clippings to fashion fake beards

  • for himself. Therefore, Socrates didn’t have a (real) beard.

  • And I just want to point out that this is an actual philosophy conspiracy theory.

  • Gorgias was a real guy, who differed with Socrates on many things, and the dispute was

  • said to have gotten personal.

  • According to accounts of the time, Gorgias actually spread the rumor that Socrates wore,

  • like, a beard-wig, in an effort to shame and discredit his rival. I mean, how could you

  • be a good thinker if you weren’t a good beard-grower.

  • Gorgiasgossip didn’t go over well with everyone, and in this instance, let’s say

  • you are skeptical about it too.

  • So you counter my counterargument with a counter-counterargument.

  • Gorgias was known for being a gossip, and for hating Socrates, and trying to make him

  • look bad. His fake beard tale seems wildly unlikely. Therefore, we can’t take Gorgias

  • statement seriously, so we should fall back on the best information we have, which is

  • that most of the men in his time and place had beards.

  • And as you can see, arguments of different styles can be used in the same exchange.

  • Like, the original argument, about Socrates probably having a beard, was inductive.

  • But this last counterargument is abductive. And that’s fine.

  • Arguments are meant to be useful, so we don’t have to use the same kind of reasoning when we argue.

  • This way of exchanging ideas through dialogue was popularized by Socrates, and so has become

  • known as the Socratic method.

  • Socrates thought dialogue was the best way to learn, and to get at truth.

  • And it’s important to note that, while philosophers have a reputation for being an argumentative

  • lot, they don’t think of the Socratic method as something that results in a winner and a loser.

  • Rather, it’s an exercise that brings both interlocutors closer to the truth.

  • The goal of the philosopher is not to win, but to find truth, so you shouldn’t be disappointed

  • if someone presents a counterargument that you can’t find a response to.

  • When that happens, a good philosopher will be grateful to their interlocutor for helping

  • them reject false beliefs and build stronger ones.

  • Today you learned about two more types of philosophical reasoning, induction and abduction.

  • Youve seen their strengths, and their weaknesses. And youve also learned about counterarguments,

  • and the Socratic method.

  • This episode is brought to you by Squarespace. Squarespace helps to create websites, blogs

  • or online stores for you and your ideas. Websites look professionally designed regardless of

  • skill level, no coding required. Try Squarespace at squarespace.com/crashcourse for a special offer.

  • Crash Course Philosophy is produced in association with PBS Digital Studios. You can head over

  • to their channel to check out amazing shows like BrainCraft, It’s OK To Be Smart, and PBS Idea Channel.

  • This episode was filmed in the Doctor Cheryl C. Kinney Crash Course Studio with the help

  • of these amazing people and our Graphics Team is Thought Cafe.

Crash Course Philosophy is brought to you by Squarespace.

字幕と単語

ワンタップで英和辞典検索 単語をクリックすると、意味が表示されます

B1 中級

議論の仕方 - 誘導と誘導。クラッシュコースの哲学#3 (How to Argue - Induction & Abduction: Crash Course Philosophy #3)

  • 133 20
    羅紹桀 に公開 2021 年 01 月 14 日
動画の中の単語