Placeholder Image

Subtitles section Play video

  • Crash Course Philosophy is brought to you by Squarespace.

  • Squarespace: Share your passion with the world.

  • You probably think you know a lot of things.

  • But do you know what it means to know something?

  • Weve spent quite a bit of time discussing beliefs and knowledge, but we haven’t really

  • been specific about what we mean when we talk about those things.

  • Thankfully, philosophers love a good definition. They have very specific and lucid ideas in

  • mind when they use terms like know or believe or proposition or justification.

  • And, about ten minutes from now, you too will know what youre really saying when you use those words.

  • But, just because these terms have been defined, doesn’t mean that philosophers aren’t still arguing over them.

  • Because you know, that’s how philosophers do.

  • Their definitions might seem kind of obvious at first, but the more you think about them,

  • the more nuanced they turn out to be.

  • Like, is having knowledge of something the same thing as being correct?

  • Or, if you believe something to be true, and it is true, does it matter if your belief in it is justified?

  • And can you be right about something without really trying?

  • Answers to these questions and more await you, as well as

  • cats!

  • [Theme Music]

  • So youve heard this already: Philosophers love a good argument.

  • But youve figured out by now that philosophers argue in a different way than, like, kindergarten

  • kids, or Internet trolls, or other people who confusearguingwith sniping back

  • and forth or just thinking up witty comebacks.

  • Nope. Philosophers have all kinds of rhetorical devices at their disposal that they can use

  • to advance an idea, or call into question the ideas of their interlocutors.

  • So in order to hold your own in a philosophical debate, youre gonna have to know the difference

  • between two things that sound like exactly the same thing: an assertion, and a proposition.

  • And youll need to be able to tell whether someone actually knows what theyre talking

  • about, or if they just believe what theyre saying might be true.

  • For example: The sentence I’m saying right now is an assertion. An assertion is a linguistic

  • acteither spoken or writtenthat has a truth value. And despite what it might

  • sound like, truth value isn’t a measure of how right something is. It’s just the

  • state of being either true, or false, or indeterminate. All declarative sentences have truth values.

  • Declarations that assert something about the past or present are either true or false.

  • And assertions about the future are indeterminate, at least when theyre expressed, because

  • no one knows if theyre right or not yet.

  • For example, I’m gonna assert thatThis cat will pee on my desk before the end of the show.”

  • That assertion has a truth value, but it’s indeterminate, because the show’s not over yet.

  • Were just gonna have to wait and see.

  • Now, all of this contrasts with other kinds of linguistic acts, like questions, which don’t assert anything.

  • This is a catis an assertion, as opposed toIs that a cat?,” which is a linguistic

  • act, but not an assertion.

  • But the substance of what you assert has a name, too.

  • The content of your assertion is your proposition. It’s the underlying meaning of what youre saying.

  • So even though an assertion itself can change, depending on say, what language it’s spoken

  • in, its meaning doesn’t change just because its outer packaging does.

  • Like, “This is a catandEste es un gato,” both assert the same proposition.

  • And a proposition is true if it asserts a claim that corresponds to reality.

  • The proposition when I assertThis is a cat,” is true if the object of thethis

  • is in fact a cat, and false if it is anything other than a cat. Like, “This is a cat.”

  • It’s worth pointing out that attitude counts, too, when youre asserting something.

  • A speaker’s mental state toward the proposition theyre making is their propositional attitude.

  • If I say, like, “This is a cat,” but I actually believe it to be a rat and I’m

  • trying to fool you, then philosophers would say that I have a propositional attitude of disbelief.

  • Whereas, if I think I’m speaking truthfully, I have a propositional attitude of belief.

  • And of course, youre not going to get very far as a philosopher unless you understand

  • the classic definition of belief itself. Based on the lingo youve learned so far today,

  • belief is just when you take a propositional attitude of truth.

  • I believe that this is a cat, if I think it’s truethat is, if my attitude is that the

  • assertion corresponds to reality. And even if I’m wrong -- even if there were an aardvark

  • on my desk, or if there weren’t a cat on my desk at all, which there isn’t anymore

  • -- if I really thought there was a cat on my desk, that would just be my belief.

  • My propositional attitude, in other words, is what determines if I have a belief.

  • What all this means is that I, like everyone else, can have false beliefs. Simply thinking

  • something doesn’t make it correspond to reality, which is what’s needed for truth.

  • But of course, the fun of arguing is showing off what you know to other people, or at least

  • producing really clever evidence to support your case.

  • So, this raises the question of what it means to actually know something, in the philosophical sense.

  • The traditional definition of knowledge is that it’s a justified true belief.

  • Note that there are three separate components here.

  • So, I have knowledge that this is a cat if: I first believe i’s a cat

  • And also that it is in fact a catthat is, my belief corresponds to reality and is

  • therefore true. And finally, I can be said to have knowledge about this cat if my belief

  • is justifiedmeaning, I have some sort of legitimate evidence to support my belief.

  • Now, weve already defined truth and belief. Justification is simply evidence, or other

  • support, for your belief. If you remember back to episode 2, youll recall that premises

  • offer justification for conclusions. And justification can come in a variety of forms. Most often,

  • it comes about through testimonyjust taking someone’s word for it. Not all testimony

  • is strong, or trustworthy, of course. But if it comes from someone who’s an expert

  • on the topic in question, you might consider the testimony to be reliable.

  • And the fact is, most of what you know about the world, you learned through testimony.

  • You took your teachersword for it when they were teaching you stuff, and the same

  • goes for every book youve ever read and every news report youve ever seen. Theyre

  • all just forms of testimony, which you accepted as justification for your knowledge, and your beliefs.

  • But justification can come in other forms, too. Another common type is first person observation

  • information you acquire through your senses.

  • If I believe that a cat is a cat, because I already have robust and well-informed beliefs

  • about cats, then, having had extensive experience with them in the past, I’m identifying the

  • cat as a cat through my direct contact with it

  • It looks, feels, acts like a cat. Ergo: cat!

  • But! Philosophy wouldn’t be any fun if the key to knowledge were that easy, right?

  • Until American philosopher Edmund Gettier came along in the 1960s, philosophers were

  • in pretty widespread agreement about the definition of knowledge -- that it’s justified true belief.

  • Because, you can believe any old thing, but in order to know something, it just makes

  • sense that you must also have evidence for your belief, and it must be true. In other

  • words, you can have a false belief, but you can’t have false knowledge. And if something

  • you thought you knew turns out not to be true, then the fact is, you never actually knew it, you just believed it.

  • And likewise, you might happen to hold a true belief, but if you don’t have any justification for it, if you

  • just accidentally happened to be right, which happens sometimesthat doesn’t count as knowledge, either.

  • Enter Edmund Gettier. Gettier wrote a short but fabulously influential paper that turned

  • the standard understanding of knowledge upside down.

  • He did this by proposing what came to be known as Gettier casessituations in which one

  • can have justified true belief, but not knowledge.

  • Which brings us to this week’s Flash Philosophy! Let’s go to the Thought Bubble.

  • Here’s one of Gettier’s original cases. Smith and Jones have both applied for the same job.

  • The president of the company told Smith that Jones will get the job. This counts as evidence;

  • the president of the company would seem to be a reliable source of this information.

  • Meanwhile, Smith counts the coins in Jonespocket and sees that there are

  • ten coins in there. Smith then forms a belief, based on his first person observational evidence

  • of the coins, as well as the testimony of the company president.

  • He comes to believe that: The person who gets the job has 10 coins in his pocket.

  • But, it turns out, the testimony of the president was false, and it’s Smith, not Jones, who gets the job.

  • AND, it just so happens, unbeknownst to Smith, that he also has 10 coins in his own pocket.

  • So, Smith has a beliefthat the person who gets the job has 10 coins in his pocket.

  • And that is justifiedbecause he counted Jonescoins, and the president told him

  • Jones was getting the job. And his belief also turns out to be truethe person who

  • got the job did have 10 coins in his pocket.

  • However, neither pieces of justification actually pointed Smith to the right answer. The president’s

  • testimony was wrong, and the 10 coins that he saw were in Jonespocket, not his own.

  • So it seems Smith simply lucked into being right.

  • Gettier argued that we now have a case of justified true belief that is not knowledge.

  • As he pointed out, you don’t KNOW something if you simply stumbled into the right answer.

  • Thanks Thought Bubble, the philosophical world was turned upside down by this idea, and philosophers

  • loving a good counterexamplebegan generating their own Gettier cases.

  • American philosopher Roderick Chisholm proposed this one:

  • Looking across a field, you see an object that looks like a sheep, and you form the

  • belief thatthere is a sheep in the field.”

  • It turns out that the object you see is actually a dog.

  • Yet, there is also a sheep, obscured from your vision by a hill.

  • So, you have a justified true belief, but the justification for your belief -- the object

  • that you sawis not a sheep. You just lucked into being right.

  • Once you understand how it works, it’s pretty easy to generate Gettier cases of your own.

  • And many philosophers today think that Gettier successfully destroyed thejustified true beliefdefinition of knowledge.

  • But even though the 1960s might seem long ago to you, remember: philosophers are in

  • the business of having millennia-long debates about stuff. So it shouldn’t surprise you

  • that the philosophical debate about this is still a-raging.

  • But if knowledge is not justified true belief, thenwhaaat is it?

  • Next time, we will look at one possible answer.

  • In the meantime, you learned about some of the key concepts we use when discussing belief

  • and knowledge. You learned what defines an assertion and a proposition, and that belief

  • is a kind of propositional attitude. We also learned about forms of justification and the

  • traditional definition of knowledge, which Edmund Gettier just totally messed with, using his Gettier cases.

  • And the cat did not pee on my desk! Because the cat was unable to spend any time at all

  • on my desk. So it turns out the assertion that I made was false.

  • But it is a true assertion that this episode was 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 {dot com} {forward slash} crash course 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 Game/Show, The Chatterbox, and Physics Girl

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

  • with the help of these awesome people and our equally fantastic graphics team is Thought Cafe.

Crash Course Philosophy is brought to you by Squarespace.

Subtitles and keywords

B1 INT US belief cat assertion knowledge justification true

The Meaning of Knowledge: Crash Course Philosophy #7

  • 2710 58
    羅紹桀   posted on 2016/05/08
Video vocabulary

Go back to previous version